Strabismus Surgery and its Complications 3540327037, 9783540327035

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David K. Coats Scott E. Olitsky

Strabismus Surgery and its Complications

1

1 23

David K. Coats  •  Scott E. Olitsky

Strabismus Surgery and its Complications

David K. Coats  •  Scott E. Olitsky

Strabismus Surgery and its Complications With 479 Figures and 40 Tables

123

David K. Coats, MD Professor of Ophthalmology and Pediatrics Cullen Eye Institute Baylor College of Medicine Chief of Ophthalmology Texas Children‘s Hospital Clinical Care Center 6701 Fannin Houston, TX 77030 USA Scott E. Olitsky, MD Chief of Ophthalmology Children‘s Mercy Hospitals and Clinics 2401 Gilham Road Kansas City, MO 64108 and Professor of Ophthalmology and Pediatrics University of Missouri – Kansas City School of Medicine and Clinical Associate Professor of Ophthalmology University of Kansas School of Medicine, Kansas City, MO USA

Library of Congress Control Number: 2007922497 ISBN

978-3-540-32703-5  Springer Berlin Heidelberg New York

This work is subject to copyright. All rights are reserved, wether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broad-casting, reproduction on microfilm or any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in it current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. Springer-Verlag is a part of Springer Science+Business Media springer.com © Springer-Verlag Berlin Heidelberg 2007 The use of general descriptive names, registed names, trademarks etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every individual case the user must check such information by consulting the relevant literature. Editor: Marion Philipp, Heidelberg, Germany Desk Editor: Martina Himberger, Heidelberg, Germany Cover design: Frido Steinen-Broo, eStudio Calamar, Spain Typesetting and Production: LE-TEX Jelonek, Schmidt & Vöckler GbR, Leipzig, Germany Printed on acid-free paper 24/3100/YL  5 4 3 2 1 0

Dedication To our wives, Evelyn and Andrea and our children Madeline, Rosalind, Jenna, Ellie and Peri. Thank you for your support, commitment and understanding, which helped us through the entire publication process.

Preface

Strabismus Surgery and its Complications is divided into two distinct sections. Part I outlines the surgical management of strabismus in 17 chapters. A full range of topics is covered including basic anatomy and physiology, surgical planning, preoperative and postoperative management, and surgical techniques. Surgical techniques are described in dedicated chapters, each richly illustrated with figures and photographs. Detailed descriptions of the basic steps of surgery as well as surgical nuances are provided. The figures and figure legends are designed to stand alone as basic surgical instruction for the surgeon who has experience with the surgical management of strabismus. More detailed instruction is available in the text for those wanting elaboration. Chapters on the use of botulinum toxin in the management of strabismus and on the medical management of strabismus conclude Part I of the textbook. Part II reviews a wide range of surgical complications, both common and uncommon, in 15 chapters. Most published reports on complications related to strabismus surgery consist of case reports or small case series. An attempt has been made to compile these numerous reports into the concise pages of this textbook in a user-friendly format, to create a single source reference on strabismus surgery complications. Advice on how to avoid and how to manage complications of strabismus surgery

is provided based on evidence-based medicine where available. Consensus and/or common sense advice is provided where evidence-based medicine is not available. A chapter on managing patients with atypical and unexpected anatomical features and a chapter on the medicolegal aspects of strabismus surgery are included. The textbook is extensively referenced and indexed to facilitate rapid identification and review of desired information. Cross-reference is made throughout each chapter to other chapters containing related information. A DVD is provided containing video footage of basic surgical techniques to compliment the information on surgical techniques provided in Part I of the textbook. The DVD also contains electronic copies of all photographs and illustrations that are unique to this textbook, divided by chapters. The owner of this textbook and DVD is free to use these photographs and illustrations in lectures and other nonpermanent teaching mediums provided that this textbook is cited as their source. Materials that were used with the permission of others has not been included on the DVD as the publisher does not have the right to authorize use of materials provided by others for use exclusively in this textbook. David K. Coats and Scott E. Olitsky

Foreword

Two well-known strabismologists present in this book their combined experience and philosophy of the surgical treatment of strabismus. In doing so they have, whenever possible, shied away from unfounded hypotheses and speculation, and relied on clinical evidence instead. If such is unavailable, a common sense approach is taught. Certain variations notwithstanding, the surgical techniques demonstrated in this volume represent the current state of the art. The reader will welcome this information and enjoy the clear illustrations. However, it is the second part, dealing with surgical complications, that sets this book apart from other recently published texts. Instructions on how to manage a complication effectively

and, more importantly, how to prevent some by avoiding certain pitfalls during the preoperative work-up of a patient are widely dispersed in the literature and not always easily located. The authors have succeeded in collecting this information and presenting it comprehensively and in an easily accessible format. This book fills a void and is a welcomed addition to the ophthalmic literature. Gunter K. von Noorden, MD Professor of Ophthalmology and Pediatrics Baylor College of Medicine Houston, Texas

Contents

Part I 1 1.1 1.1.1 1.1.2 1.1.3 1.1.4 1.1.5 1.1.6 1.2 1.3 1.4 1.4.1 1.4.2 1.5 1.6 1.6.1 1.7 1.8 1.9 1.9.1 1.9.2 1.9.3 1.9.4 1.9.5 1.9.6 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.10.1 2.10.2

Surgical Management of Strabismus Surgically Important Anatomy  . . . . . . . . . . . .   3 The Ocular Adnexa  .. . . . . . . . . . . . . . . . . . . . . . .   3 Surgical Access  .. . . . . . . . . . . . . . . . . . . . . . . . . . .   3 Eyelid Fissure Orientation  . . . . . . . . . . . . . . . . .   4 Facial Asymmetry  .. . . . . . . . . . . . . . . . . . . . . . . .   4 Pseudostrabismus  . . . . . . . . . . . . . . . . . . . . . . . . .   5 Strabismus-Induced Eyelid Changes  . . . . . . . .   6 Pseudoptosis  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   7 The Conjunctiva  . . . . . . . . . . . . . . . . . . . . . . . . . .   7 The Sclera   .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   7 Fascial System  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   9 Tenon’s Fascia  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   9 Function of Tenon’s Capsule and Orbital Connective Tissues  .. . . . . . . . . . . . . . . . . . . . . . .   9 The Rectus Muscle Pulley System  .. . . . . . . .   10 Gross Anatomy of the Extraocular Muscles    12 Rectus Muscles   . . . . . . . . . . . . . . . . . . . . . . . . .   12 Innervation of the Extraocular Muscles   .. .   15 Blood Supply to Extraocular Muscles  . . . . .   15 Surgically Important Anatomy of Individual Extraocular Muscles  . . . . . . . .   16 Medial Rectus Muscle  . . . . . . . . . . . . . . . . . . .   16 Lateral Rectus Muscle  . . . . . . . . . . . . . . . . . . .   16 Inferior Rectus Muscle  .. . . . . . . . . . . . . . . . . .   17 Superior Rectus Muscle  .. . . . . . . . . . . . . . . . .   17 Superior Oblique Muscle/Tendon  .. . . . . . . .   18 Inferior Oblique Muscle  . . . . . . . . . . . . . . . . .   18 References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   19 Physiology of Eye Movements  . . . . . . . . . . .   Axes of Ocular Rotation and Listing’s Plane    Duction Movements  .. . . . . . . . . . . . . . . . . . . .   Version Movements  . . . . . . . . . . . . . . . . . . . . .   Vergence Movements  .. . . . . . . . . . . . . . . . . . .   Basic Laws Governing Eye Movements  .. . .   Sherrington’s Law of Reciprocal Innervation  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   Herring’s Law of Equal Innervation  .. . . . . .   Donders’ Law  .. . . . . . . . . . . . . . . . . . . . . . . . . .   Cardinal and Diagnostic Positions of Gaze    Actions of Individual Muscles  . . . . . . . . . . . .   Horizontal Rectus Muscles  .. . . . . . . . . . . . . .   Vertical Rectus Muscles  .. . . . . . . . . . . . . . . . .  

21 21 22 22 22 22 23 23 23 23 24 24 24

2.10.3

The Oblique Muscles  . . . . . . . . . . . . . . . . . . . .   25 References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   26

3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9

Indications for Strabismus Surgery  . . . . . . Restoration of Binocular Vision   .. . . . . . . . . Diplopia  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Incomitant Strabismus  .. . . . . . . . . . . . . . . . . . Asthenopia  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Asymptomatic Patients  . . . . . . . . . . . . . . . . . . Compensatory Head Posture  .. . . . . . . . . . . . Miscellaneous Surgical Indications  .. . . . . . . Nystagmus  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Expansion of the Field of Vision in Patients with Esotropia  . . . . . . . . . . . . . . . . . . . . . . . . . . Psychosocial and Vocational Indications  . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

                 

4 4.1 4.1.1 4.1.2 4.2 4.2.1 4.2.2 4.2.3 4.3 4.3.1 4.3.2 4.4

Surgical Decision Making  . . . . . . . . . . . . . . . Preoperative Evaluation  .. . . . . . . . . . . . . . . . . Strabismus History  .. . . . . . . . . . . . . . . . . . . . . Ocular Motor and Sensory Examination  . . Devising the Surgical Plan  . . . . . . . . . . . . . . . Which Eye to Operate?  . . . . . . . . . . . . . . . . . . How Many Muscles to Operate?  . . . . . . . . . . Surgical “Dose”  . . . . . . . . . . . . . . . . . . . . . . . . . Special Considerations  .. . . . . . . . . . . . . . . . . . Torsion  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Incomitant Strabismus  .. . . . . . . . . . . . . . . . . . Adjustable Suture Surgery  .. . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

                         

35 35 35 35 36 36 36 37 39 39 39 39 39

5 5.1 5.2 5.3 5.4 5.5 5.6

Preoperative and Postoperative Care  .. . . . Scheduling Surgery  .. . . . . . . . . . . . . . . . . . . . . Preparation for Surgery  .. . . . . . . . . . . . . . . . . Arrival in the Operating Room  .. . . . . . . . . . Care of the Patient Following Surgery  .. . . . Timing of the First Postsurgical Visit  .. . . . . Preoperative and Postoperative Drops  .. . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

               

41 41 41 42 43 43 43 46

6 6.1 6.1.1 6.1.2 6.1.3

Anesthesia Considerations  . . . . . . . . . . . . . . Preoperative Preparation  .. . . . . . . . . . . . . . . . Laboratory Testing  . . . . . . . . . . . . . . . . . . . . . . Fasting Recommendations  . . . . . . . . . . . . . . . Preoperative Medications  . . . . . . . . . . . . . . . .

         

47 47 47 47 48

3.10

27 27 28 28 28 29 29 30 30

  30   31   32

XII

Contents

6.2 6.2.1 6.3 6.4 6.5 6.5.1 6.6 6.7 6.8 6.9 7 7.1 7.2 7.3 7.4 7.4.1 7.4.2 7.4.3 7.5 7.5.1 7.5.2 7.6 7.6.1 7.6.1.1 7.6.1.2 7.7 7.8 7.9 8 8.1 8.1.1 8.1.2 8.1.3 8.1.3.1 8.1.4 8.1.4.1 8.1.4.2 8.1.5 8.2 8.2.1

General Anesthesia  .. . . . . . . . . . . . . . . . . . . . . Induction of Anesthesia  . . . . . . . . . . . . . . . . . Retrobulbar and Peribulbar Anesthesia  .. . . Sub-Tenon’s Anesthesia  .. . . . . . . . . . . . . . . . . Topical Anesthesia  . . . . . . . . . . . . . . . . . . . . . . Modification of Surgical Technique for Topical Anesthesia  . . . . . . . . . . . . . . . . . . . Postoperative Nausea and Vomiting  .. . . . . . The Oculocardiac Reflex  .. . . . . . . . . . . . . . . . The Ocular Respiratory Reflex  .. . . . . . . . . . . Postoperative Pain  .. . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equipment, Operating Room Supplies, and Patient Preparation  .. . . . . . . . . . . . . . . . Preoperative Patient Preparation  . . . . . . . . . Draping the Patient  .. . . . . . . . . . . . . . . . . . . . . Arrangement of the Operating Room Space  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surgical Instruments  . . . . . . . . . . . . . . . . . . . . Curved Locking 0.5-mm Forceps  .. . . . . . . . Gass Muscle Hook  . . . . . . . . . . . . . . . . . . . . . . Scobee Muscle Hook  . . . . . . . . . . . . . . . . . . . . Surgical Needles   .. . . . . . . . . . . . . . . . . . . . . . . Choosing a Surgical Needle  . . . . . . . . . . . . . . Use of a Surgical Needle  . . . . . . . . . . . . . . . . . Sutures  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Absorbable Sutures  .. . . . . . . . . . . . . . . . . . . . . Collagen Sutures  . . . . . . . . . . . . . . . . . . . . . . . . Synthetic Sutures  .. . . . . . . . . . . . . . . . . . . . . . . Nonabsorbable Sutures  . . . . . . . . . . . . . . . . . . Surgical Gloves  .. . . . . . . . . . . . . . . . . . . . . . . . . Magnification  .. . . . . . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Techniques of Exposure and Closure and Preliminary Steps of Surgery  .. . . . . . What to do Prior to Making a Conjunctival Incision for Strabismus Surgery  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visual Inspection of the Patient’s Conjunctival Anatomical Landmarks  . . . . . Visual and Tactile Identification of the Rectus Muscles  .. . . . . . . . . . . . . . . . . . . Rectus Muscle Forced Traction Testing  .. . . Technique for Rectus Muscle Traction Testing  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oblique Muscle/Tendon Forced Traction Testing  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Technique for Forced Traction Testing of the Superior Oblique Muscle/Tendon  .. . Technique for Forced Traction Testing of the Inferior Oblique Muscle  . . . . . . . . . . . Spring Back Test for Slipped or Lost Muscle  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conjunctival Incisions for Rectus Muscle Surgery  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fornix (Cul-de-Sac) Incision  .. . . . . . . . . . . .

         

48 48 49 49 49

           

50 51 52 53 53 54

  57   57   57                                

58 58 61 61 62 62 62 63 63 63 63 64 64 64 64 65

  67   67   67   67   67   69   69   69   71   71   72   73

Fornix Incision Technique  . . . . . . . . . . . . . . . Initial Incision  . . . . . . . . . . . . . . . . . . . . . . . . . . Isolation of a Rectus Muscle  .. . . . . . . . . . . . . Heel or Toe Maneuver  . . . . . . . . . . . . . . . . . . . Exposure of the Muscle Insertion  .. . . . . . . . The Pole Test  .. . . . . . . . . . . . . . . . . . . . . . . . . . . Dissection of the Muscle Fascia  .. . . . . . . . . . Closure of a Fornix Incision  .. . . . . . . . . . . . . Limbal Incision  . . . . . . . . . . . . . . . . . . . . . . . . . Limbal Incision Technique  .. . . . . . . . . . . . . . Initial Incision  . . . . . . . . . . . . . . . . . . . . . . . . . . Isolation of the Muscle and Dissection of the Muscle Fascia  . . . . . . . . . . . . . . . . . . . . . 8.2.2.1.3 Closure of a Limbal Incision  . . . . . . . . . . . . . 8.2.2.1.4 Modified Limbal Incision  . . . . . . . . . . . . . . . . 8.2.2.1.5 Conjunctival Recession  .. . . . . . . . . . . . . . . . . 8.2.3 Converting a Fornix Incision into a Limbal Incision  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.3.1 Technique  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.4 Swan “Over the Muscle” Incision  . . . . . . . . . 8.2.4.1 Technique   .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Conjunctival Incisions for Oblique Surgery  References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.2.1.1 8.2.1.1.1 8.2.1.1.2 8.2.1.1.3 8.2.1.1.4 8.2.1.1.5 8.2.1.1.6 8.2.1.1.7 8.2.2 8.2.2.1 8.2.2.1.1 8.2.2.1.2

9 9.1 9.2 9.2.1 9.3 9.3.1 9.3.2 9.3.3 9.3.4 9.4 9.4.1 9.4.1.1 9.4.1.2 9.4.1.3 9.4.2 9.4.2.1 9.4.2.2 9.4.2.3 9.4.2.4 9.5 9.5.1 9.5.2 9.5.3 9.5.4 9.5.5 9.5.6

                     

73 74 75 76 76 76 76 79 79 80 80

       

80 81 82 82

           

83 83 84 84 86 86

Recession of the Rectus Muscles and Other Weakening Procedures  . . . . . . .   General Principles for Recession of the Rectus Muscles  .. . . . . . . . . . . . . . . . . . .   Measurement of Recession  .. . . . . . . . . . . . . .   Muscle Insertion Artifacts  . . . . . . . . . . . . . . .   Specific Considerations for Surgery on Individual Rectus Muscles  . . . . . . . . . . . .   Medial Rectus Muscle  . . . . . . . . . . . . . . . . . . .   Inferior Rectus Muscle  .. . . . . . . . . . . . . . . . . .   Lateral Rectus Muscle  . . . . . . . . . . . . . . . . . . .   Superior Rectus Muscle  .. . . . . . . . . . . . . . . . .   Rectus Muscle Recession Techniques  .. . . . .   Standard Rectus Muscle Recession Technique  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Placing Suture Near the Muscle Insertion     Detachment of the Muscle from the Globe    Securing the Muscle to the Sclera at its New Location  .. . . . . . . . . . . . . . . . . . . . . . . . . .   Hang-Back Recession Techniques  .. . . . . . . .   Introduction  .. . . . . . . . . . . . . . . . . . . . . . . . . . .   Securing the Muscle to the Sclera  .. . . . . . . .   Measuring the Recession  .. . . . . . . . . . . . . . . .   Hemi Hang-Back Modifications  . . . . . . . . . .   Modified Recession Procedures   .. . . . . . . . .   A- and V-Patterns  .. . . . . . . . . . . . . . . . . . . . . .   Recession Following Scleral Buckling Procedures  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Recessions in Patients with Thin Sclera  .. . .   Free Tenotomy of a Rectus Muscle   . . . . . . .   Recession with Fixation to the Adjacent Orbital Wall  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Y Splitting of the Lateral Rectus   .. . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  

87 87 88 88 88 88 88 89 89 89 90 90 90 92 92 92 94 94 95 96 96 96 96 96 97 97 97

 

10 10.1 10.1.1 10.1.2 10.1.3 10.1.4 10.2 10.3 11 11.1 11.1.1 11.1.1.1 11.1.1.2 11.1.1.3 11.2 11.2.1 11.2.1.1 11.2.2 11.2.3 11.2.4 11.2.5 11.2.6 11.2.7 11.2.8 11.3 11.3.1 11.3.2

12 12.1 12.2 12.2.1 12.2.1.1 12.2.1.2 12.2.1.3 12.2.2 12.2.2.1

Resection of the Rectus Muscles and other “Strengthening” Procedures  .. . . . . . . . . . . .   99 Technique of Rectus Muscle Resection  . . . .   99 Preparation of the Muscle for Resection  .. .   99 Resection of the Muscle  .. . . . . . . . . . . . . . . . .   99 Reattaching the Muscle to the Sclera  . . . . .   101 Dual Suture Modification  . . . . . . . . . . . . . . .   101 Resection Clamp Technique  .. . . . . . . . . . . .   102 Rectus Muscle Tuck (Plication) Technique    102 References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   103 Surgery on the Inferior Oblique Muscle    Identification and Isolation of the Inferior Oblique Muscle  . . . . . . . . . . . . . . . . . . . . . . . .   Technique  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Exposure of the Surgical Site  . . . . . . . . . . . .   Isolating the Muscle on a Muscle Hook  .. .   Dissection of the Capsule of the Inferior Oblique Muscle  . . . . . . . . . . . . . . . . . . . . . . . .   Weakening Procedures on the Inferior Oblique Muscle  . . . . . . . . . . . . . . . . . . . . . . . .   Technique of Inferior Oblique Muscle Recession  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Graded Inferior Oblique Recession  . . . . . .   Technique of Inferior Oblique Muscle Disinsertion   .. . . . . . . . . . . . . . . . . . . . . . . . . .   Technique of Inferior Oblique Myectomy    Technique of Inferior Oblique Myotomy     Technique of Denervation and Extirpation    Technique of Inferior Oblique Anterior Transposition  .. . . . . . . . . . . . . . . . . . . . . . . . .   Technique for Nasal Myotomy of the Inferior Oblique Muscle  . . . . . . . . . .   Technique for Anterior and Nasal Transposition of the Inferior Oblique Muscle  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Strengthening Procedures on the Inferior Oblique Muscle  . . . . . . . . . . . . . . . . . . . . . . . .   Technique for Advancement of the Inferior Oblique Muscle With and Without Resection   . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Technique for Tucking Procedure on the Inferior Oblique Muscle  .. . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   Surgery on the Superior Oblique Tendon    Forced Traction Testing of the Superior Oblique Tendon  .. . . . . . . . . . . . . . . . . . . . . . .   Superior-Oblique-Strengthening Procedures  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Technique of Superior Oblique Tucking Procedure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Identifying the Superior Oblique Tendon    Isolation of the Superior Oblique Tendon    Tucking of the Superior Oblique Tendon    Technique for the Fells Modification of the Harada-Ito Procedure  .. . . . . . . . . . . .   Using Adjustable Sutures  .. . . . . . . . . . . . . . .  

105 105 106 106 107

Contents

12.2.3 12.3 12.3.1 12.3.2 12.3.3 12.3.4 12.3.5

Technique for the Classic Harada-Ito Procedure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Superior-Oblique-Weakening Procedures    Technique of Superior Oblique Tenotomy and Tenectomy  .. . . . . . . . . . . . . . . . . . . . . . . .   Technique for Guarded Superior Oblique Tenotomy  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Technique for Superior Oblique Tendon Expander  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Technique for Superior Oblique Recession    Technique for Superior Oblique Posterior Tenotomy/Tenectomy  . . . . . . . . . . . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .  

116

Transposition Procedures  . . . . . . . . . . . . . .   Surgical Exposure for Transposition Procedures  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   13.2 Transposition Surgery Techniques  . . . . . . .   13.2.1 Technique for Full Tendon Transposition    13.2.2 Technique for Full Tendon Transposition with Posterior Fixation Suture Augmentation (Foster Procedure)  . . . . . . .   13.2.3 Technique for Full Tendon Transposition with Lateral Rectus Muscle Fixation  . . . . .   13.2.4 Techniques for Vessel-Sparing Full Tendon or Near Full Tendon Transposition  . . . . . .   13.2.5 Technique for Hummelsheim-Type Transposition  .. . . . . . . . . . . . . . . . . . . . . . . . .   13.2.5.1 Augmentation of a Hummelsheim-Type Procedure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   13.2.6 Technique for the Knapp Transposition Procedure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   13.2.7 Technique for the Jensen Procedure  .. . . . .   13.2.7.1 Vessel-Sparing Modification of the Jensen Procedure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   13.2.8 Technique for Superior Oblique Tendon Transposition  .. . . . . . . . . . . . . . . . . . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .  

116

14 14.1

107 108 109 109 111 111 112 113 113 115 115

116 117 119 119 119 119 120 120 121 122 123

13 13.1

XIII

124 124 126 126 127 128 128 129 131 132 133 133 133 134 134 135 135 136 136 137 138 139

Adjustable Suture Techniques  . . . . . . . . . .   141 Modifications of the Surgical Site for Adjustable Sutures  . . . . . . . . . . . . . . . . . .   141 14.1.1 Surgical Site Modifications for Adjustable Sutures Through a Limbal Incision   .. . . . .   142 14.1.2 Surgical Site Modifications for Adjustable Sutures Through a Fornix Incision   . . . . . .   142 14.1.3 Bucket Handle Globe Manipulation Suture    142 14.2 Adjustable Suture Techniques  . . . . . . . . . . .   145 14.2.1 Technique for Bow-Type Adjustable Sutures  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   145 14.2.2 Technique for Cinch Knot Adjustable Sutures  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   145 14.2.3 Technique for Traction Knot Adjustable Sutures  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   145 14.2.4 Technique for Ripcord Adjustable Sutures     145 14.2.4.1 Recession Technique  . . . . . . . . . . . . . . . . . . .   148 14.2.4.2 Resection Technique  . . . . . . . . . . . . . . . . . . .   148 References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   150

XIV

Contents

15 15.1 15.2 15.3 15.4 15.5 15.6 15.7

16 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 17 17.1 17.1.1 17.1.2 17.1.3 17.1.4 17.2 17.2.1 17.2.2 17.3 17.4

Special Procedures  .. . . . . . . . . . . . . . . . . . . . Periosteal Flap Fixation of the Globe  .. . . . Recession and Periosteal Fixation of a Rectus Muscle  . . . . . . . . . . . . . . . . . . . . . Postoperative Traction Sutures  . . . . . . . . . . Marginal Tenotomy/Myotomy  .. . . . . . . . . . Treatment of Esotropia and Hypotropia Associated with High Axial Myopia  .. . . . . Horizontal Transposition of the Vertical Rectus Muscles to Treat Isolated Ocular Torticollis/Torsion  . . . . . . . . . . . . . . . . . . . . . Posterior Fixation Suture (Retroequatorial Myopexy, Fadenoperation)  .. . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . The Use of Botulinum Neurotoxin in the Treatment of Strabismus  . . . . . . . . . Mechanism of Action   . . . . . . . . . . . . . . . . . . Effect on the Neuromuscular Junction  . . . Other Actions of Botulinum Neurotoxin  History of Botulinum Neurotoxin in the Treatment of Strabismus  . . . . . . . . . . Injection Techniques   .. . . . . . . . . . . . . . . . . . Treatment of Strabismus with Botulinum Toxin  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Botulinum Toxin in the Treatment of Nystagmus  . . . . . . . . . . . . . . . . . . . . . . . . . . Complications  . . . . . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . Nonsurgical Treatment of Strabismus  .. . Spectacles   .. . . . . . . . . . . . . . . . . . . . . . . . . . . . Accommodative Esotropia   .. . . . . . . . . . . . . Poor Uncorrected Visual Acuity  .. . . . . . . . Over Minus Lens Therapy  .. . . . . . . . . . . . . . Bifocal Lenses  .. . . . . . . . . . . . . . . . . . . . . . . . . Occlusion Therapy  . . . . . . . . . . . . . . . . . . . . . Part-Time Occlusion  . . . . . . . . . . . . . . . . . . . Full-Time Occlusion  .. . . . . . . . . . . . . . . . . . . Orthoptic Therapy  . . . . . . . . . . . . . . . . . . . . . Prism Correction  .. . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

  151   151   151   153   153   154   156   156   158        

159 159 159 159

  159   160   161   162   163   163                        

165 165 165 165 166 166 166 166 167 167 168 169

       

173 173 173 173

       

174 174 174 175

Part II Complications of Strabismus Surgery Preoperative Management Errors  .. . . . . . Errors in Preoperative Decision-Making   Field of Single Vision   .. . . . . . . . . . . . . . . . . . Monocular Diplopia  .. . . . . . . . . . . . . . . . . . . Nystagmus and Strabismus in Patients with a Compensatory Head Posture  .. . . . . 18.1.4 Restrictive Strabismus  . . . . . . . . . . . . . . . . . . 18.1.5 Paralytic Strabismus  .. . . . . . . . . . . . . . . . . . . 18.1.6 Torsional Strabismus  . . . . . . . . . . . . . . . . . . . 18.1.7 Misdiagnosis of Apparent Duction Abnormalities  .. . . . . . . . . . . . . . . . . . . . . . . . . 18.1.7.1 Apparent Duction Deficits  . . . . . . . . . . . . . . 18.1.7.2 Pseudo Oblique Overaction  .. . . . . . . . . . . . 18 18.1 18.1.1 18.1.2 18.1.3

  176   176   176

Errors in Measurements of Strabismus  . . . Primary Position Measurement Errors  . . . Krimsky and Hirschberg Tests  .. . . . . . . . . . Prism Measurement Errors   .. . . . . . . . . . . . Improper Prism Position  .. . . . . . . . . . . . . . . Addition of Stacked Prisms  . . . . . . . . . . . . . Addition of Prisms Held in Front of Both Eyes  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spectacle-Induced Measurement Errors  . . 18.2.4 18.2.4.1 Large Refractive Errors  . . . . . . . . . . . . . . . . . 18.2.4.2 Unrecognized Prism  .. . . . . . . . . . . . . . . . . . . 18.2.5 Duction Limitation Errors  . . . . . . . . . . . . . . 18.2.6 Poor Fixation  . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.7 Poor Cooperation  .. . . . . . . . . . . . . . . . . . . . . 18.3 Incomplete Diagnosis  .. . . . . . . . . . . . . . . . . . 18.4 Management Errors at the Time of Surgery  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.1 Marking the Surgical Site  . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

18.2 18.2.1 18.2.2 18.2.3 18.2.3.1 18.2.3.2 18.2.3.3

19

Anterior Segment and Ocular Surface Complications of Strabismus Surgery  . . . 19.1 Corneal Complications  . . . . . . . . . . . . . . . . . 19.1.1 Dellen  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.1.2 Corneal Abrasions  . . . . . . . . . . . . . . . . . . . . . 19.1.3 Corneal Ulcer  .. . . . . . . . . . . . . . . . . . . . . . . . . 19.1.4 Filamentary Keratitis  . . . . . . . . . . . . . . . . . . . 19.1.5 Reduced Endothelial Cell Count  .. . . . . . . . 19.1.6 Corneal Toxicity  . . . . . . . . . . . . . . . . . . . . . . . 19.2 Conjunctival Complications  .. . . . . . . . . . . . 19.2.1 Inadvertent Advancement of the Plica Semilunaris Conjunctivae   . . . 19.2.1.1 Limbal Incision Closure Tips  .. . . . . . . . . . . 19.2.2 Retraction and Coiling  . . . . . . . . . . . . . . . . . Chemosis  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.3 19.2.3.1 Technique for Correction of Prolapsed Inferior Conjunctiva  .. . . . . . . . . . . . . . . . . . . 19.2.4 Pyogenic Granuloma  . . . . . . . . . . . . . . . . . . . 19.2.5 Prolapse of Tenon’s Fascia  .. . . . . . . . . . . . . . 19.2.6 Epithelial Inclusion Cyst   .. . . . . . . . . . . . . . . 19.2.7 Sudoriferous Cyst  . . . . . . . . . . . . . . . . . . . . . . 19.2.8 Subconjunctival Abscess  .. . . . . . . . . . . . . . . 19.2.9 Conjunctival Adhesions  . . . . . . . . . . . . . . . . 19.2.10 Primary Amyloidosis  .. . . . . . . . . . . . . . . . . . 19.2.11 Subconjunctival Foreign Bodies  . . . . . . . . . 19.2.12 Conjunctival Buttonholes  .. . . . . . . . . . . . . . 19.3 Scleral Complications  . . . . . . . . . . . . . . . . . . 19.3.1 Grey Spot  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2 Scleral Ridge  .. . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.3 Scleral Dellen  .. . . . . . . . . . . . . . . . . . . . . . . . . 19.3.4 Scleritis  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.5 Agyrosis  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4 Anterior Segment/Intraocular Complications  . . . . . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 20.1 20.2

           

176 176 177 177 177 178

               

178 178 178 180 180 181 181 182

  182   182   183                  

185 185 185 186 186 188 188 188 188

       

188 190 191 191

                               

192 193 193 194 196 197 197 198 198 198 198 198 199 200 200 200

  200   200

Anterior Segment Ischemia  .. . . . . . . . . . . .   203 Blood Supply of the Anterior Segment  . . .   203 Incidence   . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   204

 

20.3 20.4 20.5 20.6 20.7 20.7.1 20.7.2 20.7.3 20.7.4 20.7.5 20.8 21 21.1 21.2 21.3 21.3.1 21.4 21.5 21.6 21.7 21.8 22 22.1 22.1.1 22.1.2 22.2 22.3 22.4 22.5 22.6 22.7 22.8 22.9 22.10 23 23.1 23.1.1 23.1.2 23.1.3 23.2 23.2.1 23.2.1.1 23.3 23.4 23.5

Risk Factors and Prevention   . . . . . . . . . . . . Signs and Symptoms  .. . . . . . . . . . . . . . . . . . . Treatment  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prevention of Anterior Segment Ischemia   Mitigating Risk Through Surgical Planning  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conjunctival incision   . . . . . . . . . . . . . . . . . . Minimizing Number of Muscles Operated in an Eye  .. . . . . . . . . . Sparing of the Anterior Ciliary Arteries  .. . Mechanical Fixation of the Globe  .. . . . . . . Staging of Surgery  .. . . . . . . . . . . . . . . . . . . . . Summary and Recommendations  .. . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

       

204 205 205 206

Scleral Perforation and Penetration  .. . . . Risk Factors  . . . . . . . . . . . . . . . . . . . . . . . . . . . Clinical Evidence of Perforation  . . . . . . . . . Potential Sequelae of Scleral and Eye Wall Perforation   .. . . . . . . . . . . . . . . . . . . . . . . . . . . Retinal Detachment  . . . . . . . . . . . . . . . . . . . . Vitreous and Anterior Chamber Hemorrhage  .. . . . . . . . . . . . . . . . . . . . . . . . . . Endophthalmitis  . . . . . . . . . . . . . . . . . . . . . . . Anterior Chamber Perforation  . . . . . . . . . . Prevention  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . Treatment  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

  211   214   217

  206   206            

206 207 208 209 209 209

  218   218

Contents

23.6 23.6.1 23.6.2 23.7

  243   243   246

Hemorrhage  .. . . . . . . . . . . . . . . . . . . . . . . . . . Introduction  .. . . . . . . . . . . . . . . . . . . . . . . . . . Risk Factors  . . . . . . . . . . . . . . . . . . . . . . . . . . . Eyelid Hemorrhages  .. . . . . . . . . . . . . . . . . . . Orbital Hemorrhage  .. . . . . . . . . . . . . . . . . . . Muscle Hemorrhage  .. . . . . . . . . . . . . . . . . . . Vortex Vein Hemorrhage  . . . . . . . . . . . . . . . Subconjunctival Hemorrhage  . . . . . . . . . . . Intraocular Hemorrhage  .. . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

                   

247 247 247 247 248 249 250 250 250 250

25 25.1 25.2 25.3 25.4 25.5

Adherence and Adhesion Syndromes  . . . Fat Adherence Syndrome  . . . . . . . . . . . . . . . Incidence  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prevention  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . Treatment  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Miscellaneous Adhesion Syndromes Due to Strabismus Surgery  .. . . . . . . . . . . . . Adhesion Syndrome Following Superior Oblique Tendon Expander Surgery  . . . . . . Inferior Oblique Inclusion Syndrome  . . . . J-Deformity of a Rectus Muscle  .. . . . . . . . . Scarring of Tenon’s Capsule and Conjunctiva  . . . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

         

253 253 253 254 255

218 219 219 219 220 220

         

223 223 223 223 224

25.5.2 25.5.3 25.5.4

         

227 229 230 230 230

26

       

231 231 231 231

26.3

Slipped and Lost Muscles  .. . . . . . . . . . . . . .   The Slipped Muscle  .. . . . . . . . . . . . . . . . . . . .   Presentation and Diagnosis  . . . . . . . . . . . . .   Treatment  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Prevention  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   The Lost Rectus Muscle  .. . . . . . . . . . . . . . . .   Clinical Presentation and Diagnosis  . . . . .   Intraoperative Muscle Loss  .. . . . . . . . . . . . .   The Snapped or Torn Extraocular Muscle    Delayed Loss of an Extraocular Muscle  .. .   Traumatic Disinsertion of an Extraocular Muscle   .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  

233 233 233 237 237 238 238 239 240 241

26.6 26.7 26.8 26.9

242

  242   242

24 24.1 24.2 24.3 24.4 24.5 24.6 24.7 24.8

           

Postoperative Infection  . . . . . . . . . . . . . . . . Risk Factors  . . . . . . . . . . . . . . . . . . . . . . . . . . . Glove Perforation  . . . . . . . . . . . . . . . . . . . . . . Operating Room Equipment and Supplies  Endophthalmitis  . . . . . . . . . . . . . . . . . . . . . . . Periocular Infection (Orbital and Preseptal Cellulitis)  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scleritis  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subconjunctival Abscess  .. . . . . . . . . . . . . . . Corneal Ulcer  .. . . . . . . . . . . . . . . . . . . . . . . . . Concurrent Systemic Infections  . . . . . . . . . Subacute Bacterial Endocarditis Prophylaxis  .. . . . . . . . . . . . . . . . . . . . . . . . . . . Concurrent Surgeries  .. . . . . . . . . . . . . . . . . . Special Situations  .. . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Surgical Treatment of the Lost Extraocular Muscle  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Retrieval and Reattachment  .. . . . . . . . . . . . Transposition Procedures when Attempted Retrieval and Reattachment is Unsuccessful  .. . . . . . . . . . . . . . . . . . . . . . . . Stretched Scar Syndrome  . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

XV

25.5.1

26.1 26.2

26.4 26.5

27 27.1 27.2 27.3 27.4

  255   255   255   256   256   256

Complications Involving the Ocular Adnexa  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Eyelid Retraction and Advancement Following Vertical Rectus Muscle Surgery    Aberrant Regeneration of the Third Cranial Nerve  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Eyelid Changes Following Horizontal Rectus Muscle Surgery  .. . . . . . . . . . . . . . . . .   Ptosis and Pseudoptosis  .. . . . . . . . . . . . . . . .   Lid Changes Associated with Inferior Oblique Muscle Anterior Transposition  . .   Eyelid Adhesions  .. . . . . . . . . . . . . . . . . . . . . .   Preseptal Cellulitis  . . . . . . . . . . . . . . . . . . . . .   Eyelid Ecchymosis and Hematoma  .. . . . . .   Burns  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .   Unexpected and Atypical Anatomy  . . . . . Congenital Aplasia of the Extraocular Muscles  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Craniofacial Dysostosis Syndromes  .. . . . . Aplasia of the Superior Oblique Muscle and/or Tendon  .. . . . . . . . . . . . . . . . . . . . . . . . Aplasia of the Inferior Oblique Muscle  . . .

259 259 261 262 263 264 264 265 265 265 266

  267   267   267   268   269

XVI

Contents

27.5 27.6 27.7 27.8

Aplasia of the Inferior Rectus Muscle  . . . .   Aplasia of the Superior Rectus Muscle  .. . .   Aplasia of the Horizontal Rectus Muscle  .   Abnormal Muscle Paths and Heterotopic Rectus Muscle Pulleys  .. .   27.9 Abnormal Extraocular Muscle Insertions    27.9.1 Inferior Oblique Muscle   .. . . . . . . . . . . . . . .   27.9.2 Superior Oblique Muscle/Tendon  .. . . . . . .   27.9.3 Bifid Rectus Muscles  .. . . . . . . . . . . . . . . . . . .   27.9.4 Abnormal Rectus Muscle Insertions  . . . . .   27.10 Accessory Muscle  . . . . . . . . . . . . . . . . . . . . . .   27.11 Atypical Restrictive Strabismus  .. . . . . . . . .   27.11.1 Thyroid-Related Ophthalmopathy  . . . . . . .   27.11.1.1 Oblique Muscle Involvement  .. . . . . . . . . . .   27.11.2 Superior Rectus Muscle Involvement  .. . . .   27.11.2.1 Exotropia in Thyroid-Related Ophthalmopathy  .. . . . . . . . . . . . . . . . . . . . . .   27.12 Strabismus Following Scleral Buckling Surgery  . . . . . . . . . . . . . . . .   27.13 Hydrogel Explants  .. . . . . . . . . . . . . . . . . . . . .   27.14 Occult Orbital Fractures  . . . . . . . . . . . . . . . .   27.15 Strabismus Associated with Glaucoma Setons  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27.16 High Myopia Related Strabismus  . . . . . . . .   27.17 Brown Syndrome  .. . . . . . . . . . . . . . . . . . . . . .   Congenital Extraocular Muscle Fibrosis  . .   27.18 27.19 Miscellaneous Muscle Abnormalities  .. . . .   27.20 Abnormalities of the Sclera  .. . . . . . . . . . . . .   27.20.1 Thin Sclera  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .  

270 271 271 272 272 272 272 273 273 273 274 274 274 275 276 277 279 279 279 280 280 281 282 282 282 282

28 28.1 28.2 28.3 28.4 28.5 28.6 28.7 28.8

Anesthesia-Related Complications  .. . . . . General Anesthesia  .. . . . . . . . . . . . . . . . . . . . Malignant Hyperthermia  . . . . . . . . . . . . . . . Postoperative Nausea and Vomiting  .. . . . . Unintended Intraoperative Awareness  .. . . Local Anesthesia  . . . . . . . . . . . . . . . . . . . . . . . Retrobulbar and Peribulbar Injection  . . . . Sub-Tenon’s Anesthesia  .. . . . . . . . . . . . . . . . Topical Anesthesia  . . . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

                   

285 285 285 286 287 287 287 288 288 288

29 29.1 29.2 29.3 29.4 29.5

Unexpected Postoperative Alignment  .. . Prism Problems   . . . . . . . . . . . . . . . . . . . . . . . Unsuspected Myasthenia Gravis  .. . . . . . . . Postoperative Duction Limitation  .. . . . . . . Concurrent Neurological Disease  .. . . . . . . Diplopia Associated with the Chiari Malformation  .. . . . . . . . . . . . . . . . . . . . . . . . . Spectacle-Induced Prism and Refractive Issues  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Undetected Prism  .. . . . . . . . . . . . . . . . . . . . .

         

291 291 291 291 292

29.6 29.6.1

Anisometropia  .. . . . . . . . . . . . . . . . . . . . . . . . Unsuspected Torsion, Aniseikonia, and Central Disruption of Fusion  .. . . . . . . Torsion  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aniseikonia  .. . . . . . . . . . . . . . . . . . . . . . . . . . . Central Disruption of Fusion   . . . . . . . . . . . Under- and Overcorrections  . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

  293            

293 293 293 293 293 294

30 30.1 30.2 30.3 30.4

Altered Postoperative Vision  . . . . . . . . . . . Anterior Segment Ischemia  . . . . . . . . . . . . . Cystoid Macular Edema  . . . . . . . . . . . . . . . . Unrecognized Diplopia  . . . . . . . . . . . . . . . . . Change in Refractive Error  .. . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

           

295 295 295 296 296 297

31 31.1 31.2 31.3

Persistent Diplopia Following Surgery  . .   The Double Vision Seeking Patient  . . . . . .   Diplopia Due to Incomitant Strabismus  . .   Central Disruption of Fusion (Horror Fusionis)  . . . . . . . . . . . . . . . . . . . . . .   Dragged-Fovea Diplopia Syndrome  .. . . . .   Aniseikonia  .. . . . . . . . . . . . . . . . . . . . . . . . . . .   Spectacle-Induced Diplopia  . . . . . . . . . . . . .   Unrecognized Torsional Diplopia  .. . . . . . .   Anomalous Retinal Correspondence  .. . . .   Identifying the Patient at High Risk for Intractable Diplopia  .. . . . . . . . . . . . . . . .   Closed Head Injury  .. . . . . . . . . . . . . . . . . . . .   Prolonged Monocular Visual Deprivation    Markedly Incomitant Strabismus  . . . . . . . .   History of Anti-Suppression Therapy  . . . .   Procedures Which May Induce Permanent Diplopia  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Managing the Patient with Intractable Diplopia  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .  

299 299 300

29.6.2 29.7 29.7.1 29.7.2 29.7.3 29.7.4

31.4 31.5 31.6 31.7 31.8 31.9 31.9.1 31.9.2 31.9.3 31.9.4 31.10 31.11

32

Medicolegal Aspects of Strabismus Surgery  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Informed Consent   . . . . . . . . . . . . . . . . . . . . . Written Consent  . . . . . . . . . . . . . . . . . . . . . . . Medical Malpractice   . . . . . . . . . . . . . . . . . . . Intentional Torts  . . . . . . . . . . . . . . . . . . . . . . . Battery   .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unintentional Torts  . . . . . . . . . . . . . . . . . . . . Elements of Negligence  .. . . . . . . . . . . . . . . . The Medical Record  . . . . . . . . . . . . . . . . . . . . The Unhappy Patient  . . . . . . . . . . . . . . . . . . . References  .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

                     

300 300 301 301 301 302 304 304 304 304 305 305 305 306 307 307 307 308 308 308 308 309 309 309 309

  292

32.1 32.2 32.3 32.4 32.4.1 32.5 32.5.1 32.6 32.7

  292   292

Subject Index  .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   311

Part I

Surgical Management of Strabismus

Chapter

Surgically Important Anatomy

1

1 A clear grasp of the relevant anatomy and an understanding of important anatomical variations are obvious prerequisites for the strabismus surgeon. The strabismus surgeon must not only be familiar with the anatomy of the extraocular muscles, but must also be cognizant of adjacent structures in the orbit and the ocular adnexa. Much of the anatomy that the strabismus surgeon must be familiar with is covered routinely during the normal course of training in an ophthalmology residency program. This standard training should be considered as an introduction. The strabismus surgeon needs to understand many intricacies of the ocular anatomy as they relate to cause and surgical treatment in order to both effectively plan and execute surgery to correct strabismus. A clear understanding of the implications of the palpebral fissures and orbital shape, for example, is important not only because it may affect surgical access to the extraocular muscles, but because anatomical clues may also provide insight about the etiology of the ocular motility disturbance. Indeed, many patients who present with concerns about ocular misalignment actually have pseudostrabismus because of an illusion created by normal and abnormal ocular adnexa. Additionally, unwanted lid fissure changes induced by strabismus surgery are not uncommon because of the close anatomical relationship between the extraocular muscles and eyelid structures. The implications for changes in eyelid shape and/or position following strabismus surgery should be clearly understood, and reviewed with patients preoperatively, when applicable. While the conjunctiva is often inappropriately considered to be little more than a structure that must be incised to gain surgical access to the extraocular muscles, an understanding and recognition of key features of the conjunctival anatomy, especially nasally, is necessary to devise and carry out appropriate conjunctival incisions to optimize access to the extraocular muscles, to assure proper conjunctival closure and good cosmesis following surgery, and to avoid scarring and contracture of the conjunctiva which can produce unanticipated restrictive strabismus postoperatively. We have encountered many patients who have obtained good alignment following strabismus surgery but who were unhappy with the results of surgery because of the appearance of their conjunctiva afterwards. Tenon’s fascia and other orbital tissues have a direct impact on the function of the extraocular muscles and on ocular alignment, both by helping to direct and alter the paths of the extraocular muscles through the formation of soft tissue pul-

leys, and by transmitting forces generated by contraction of the extraocular muscles indirectly to the sclera. Even a “lost” rectus muscle may continue to have a minor to moderate ability to move the eye through these secondary attachments with the globe, despite complete disruption of the normal anatomical insertion. This chapter will highlight key elements of ocular and orbital anatomy that are important for the strabismus surgeon to understand. Major structures of anatomical importance involving the eyelids, conjunctiva, Tenon’s fascia, and other orbital tissues will be reviewed, concluding with an assessment and review of key elements of the ocular and orbital anatomy that the strabismus surgeon may encounter during surgery on individual extraocular muscles. Cross-referencing to chapters on the recognition, prevention, and treatment of strabismus surgery complications is made throughout the chapter as appropriate.

1.1 The Ocular Adnexa 1.1.1 Surgical Access Rarely does the shape or size of the palpebral fissures significantly alter the surgical approach for strabismus surgery. However, small palpebral fissures and deeply set eyes can make surgical access more difficult. Recognition of these features prior to surgery can be important in helping the surgeon to estimate the amount of time the procedure will take and in determining the skill level of the surgical assistant that is needed during surgery. Surgical access is most likely to be compromised when performing large recessions on the medial rectus muscles of small infants and when operating on elderly patients with significant lid fissure abnormalities and deeply set eyes as a result of orbital fat atrophy. While these anatomical issues should not deter the surgeon from performing surgery, they may impact the surgical plan. A limbal incision, which provides broad, unimpeded access to the extraocular muscles for example, may be a good option to facilitate surgery in the two examples cited. Just as small palpebral fissures and deeply set eyes may limit surgical access, prominent eyes, and wide palpebral fissures may facilitate access. Proptosis in a patient with thyroid-re-



Surgically Important Anatomy

lated ophthalmopathy may be associated with greater ocular discomfort and a greater risk for exposure keratopathy following surgery.

Chapter 1

The recognition of atypical strabismus in a patient with a craniofacial abnormality may prompt consideration of neuroimaging studies to evaluate for abnormalities in muscle positions within the orbit, absent muscles, and other abnormalities [2] (Chap. 27).

1.1.2 Eyelid Fissure Orientation Careful analysis of the ocular adnexa can provide import clues as to the etiology of strabismus in some patients and may help guide preoperative evaluation and surgical management. For example, strabismus is not only common in patients with craniofacial syndromes, but it is often atypical, involving both horizontal and/or vertical deviations and is commonly associated with marked overaction and/or underaction of the oblique muscles that may be secondary to incyclorotation or excyclorotation of the globe in these cases or due to the absence of one or more oblique muscles and/or tendons, most commonly the superior oblique tendon. A combination of several different factors may lead to the development of strabismus in patients with craniofacial syndromes. Recognizing that the patient has strabismus due to a craniofacial skeletal abnormality should prompt the surgeon to carefully evaluate for an A- or V-pattern, oblique muscle dysfunction, and other disturbances. Often the facial features of a patient with a craniofacial abnormality will be subtle, but may still have an important impact on both the etiology and treatment of strabismus. In general, patients with significant down-slanting palpebral fissures tend to demonstrate apparent inferior oblique overaction during adduction and may have V-pattern strabismus (>Fig. 1.1), while those with up-slanting palpebral fissures tend to demonstrate apparent superior oblique overaction during adduction and may have A-pattern strabismus. Patients with spina bifida, for example, commonly have A-pattern horizontal strabismus in association with up-slanting palpebral fissures [1] (>Fig. 1.1). Anatomical variation in paths of the extraocular muscle through the orbit have been shown to be altered and heterotopia of rectus muscle pulleys has been implicated as the cause of A-pattern horizontal strabismus in these patients [1].

1.1.3 Facial Asymmetry Facial asymmetry has been reported in association with congenital superior oblique palsy [3, 4]. It is manifested as midfacial hemihypoplasia on the side of the face in the direction of the head tilt. Thus it most commonly is seen on the side of the face opposite the superior oblique palsy. The nose and mouth are typically deviated toward the hypoplastic side of the face (>Fig. 1.2). This facial asymmetry is thought to be associated with congenital and early-onset superior oblique palsies. This facial asymmetry has been postulated to occur as a result of a chronic head tilt from a young age [5] though others have questioned its association at all [6]. Many strabismus surgeons believe that the presence of facial asymmetry as characterized above and/or the presence of a chronic head tilt in a patient with a recently diagnosed superior oblique palsy is sufficient evidence to warrant a diagnosis of congenital or early-onset superior oblique palsy, negating the need for neurologic evaluation. Patients with congenital superior oblique palsy are often found to have a “floppy” or otherwise abnormal superior oblique tendon at surgery [7]. This finding may help to dictate the surgical approach used in these patients. Patients with unilateral coronal synostosis (plagiocephaly) often present with an ocular motility condition that clinically resembles superior oblique muscle palsy. The apparent “palsy” is due to asymmetric orbital growth. The trochlea on the involved side does not advance anteriorly as would occur in a normal orbit where it ultimately is located anterior to the equator of the globe. The resulting position of the trochlea more posterior than normal relative to the equator of the globe results in a reduction of depressing action during contraction

Fig. 1.1a,b. Lid fissure anatomy may provide initial clues in evaluating a patient with strabismus. a V-pattern strabismus and apparent inferior oblique overaction in a patient with down-slanting palpebral fissures. b A-pattern strabismus is common in patients with up-slanting palpebral fissures

 

1.1  The Ocular Adnexa

gist may be the first physician to recognize the presence of the condition, prompting referral to a neurosurgeon for surgical treatment. Flattening of the forehead and mild to moderate prominence of the eye resulting from the presence of a shallow orbit on the involved side, and skull asymmetry are noteworthy findings in these patients. Neurosurgical treatment of coronal synostosis may alter ocular alignment, changing the ultimate surgical plan, or even eliminating the need for strabismus surgery altogether.

1.1.4 Pseudostrabismus

Fig. 1.2. Facial asymmetry in a patient with a history of early-onset superior oblique palsy. Note the midfacial hemihypoplasia on the side of the face toward the head tilt

of the superior oblique muscle (>Fig. 1.3). This mechanical disadvantage can result clinically in an ocular motility disturbance that resembles a superior oblique palsy [8]. Patients will usually present with a head tilt and frequently will have facial asymmetry that subtly resembles the facial asymmetry that has been reported with early-onset superior oblique palsy. It is important to recognize the difference in presentation of patients with unilateral coronal synostosis because the ophthalmolo-

Both normal and pathologic variations in eyelid fissure anatomy can produce the appearance of strabismus, despite normal alignment of the visual axis of the two eyes. In a pediatric ophthalmology practice, diagnosis of pseudoesotropia in infants with large epicanthal folds is probably the most common example (>Fig. 1.4a). Family members and primary care physicians alike may believe that strabismus is present because they do not see much “white” on the nasal aspect of the eye compared to the temporal aspect of the eye. Good advice to parents in this setting is to “ignore the white and look at the light,” pointing out the need to assess the corneal light reflex. After careful explanation, most parents can often recognize that the position and shape of the eyelids and other ocular adnexal structures can produce the appearance of strabismus, when in fact the eyes are aligned. It is sometimes difficult, however, to convince

Fig. 1.3. Failure of the trochlea to advance anterior to the equator in a patient with unilateral coronal synostosis may result in reduction of depressing action on the globe with contraction of the superior oblique muscle





Surgically Important Anatomy

Chapter 1

Fig. 1.4a–d. Pseudostrabismus: a pseudoesotropia, b with a simple demonstration to parents that the epicanthal folds are producing the

illusion of strabismus; c pseudoexotropia due to eyelid fissure asymmetry, and d pseudohypotropia due to right upper lid retraction.

doubting parents that the eyes are straight. A simple demonstration of tightening the epicanthal folds by pinching the bridge of the nose can be an effective tool in convincing parents that the crossing that they see is an illusion (>Fig. 1.4b). In the same way that prominent epicanthal folds can create the illusion of esotropia, abnormalities involving the lateral canthal area can create the illusion of exotropia. Temporal ptosis and dermatochalasis with prominent temporal hooding are just two examples of conditions that may produce the illusion of exotropia. An example of lid fissure asymmetry causing pseudoexotropia is shown in Fig. 1.4c. The illusion of vertical strabismus can be created by asymmetric ptosis and/or upper or lower eyelid retraction (>Fig. 1.4d). Similarly, changes in

the lid fissures induced by strabismus surgery, especially when asymmetric, can be distressing to patients postoperatively (Chap. 26), both because of the presence of the eyelid asymmetry itself and because the patient may continue to believe that strabismus is still present, when in fact the eyes are actually well aligned.

1.1.5 Strabismus-Induced Eyelid Changes One of the hallmarks of thyroid-related ophthalmopathy is retraction of one or more of the eyelids (>Fig. 1.5). While stra-

 

Fig. 1.5. Eyelid retraction in a patient with thyroid-related ophthalmopathy

bismus due to thyroid-related ophthalmopathy is generally obvious, subtle ocular motility disturbances can present. The presence of eyelid retraction may be the initial clue that the problem is due to thyroid-related ophthalmopathy, and can significantly alter key aspects of treatment including preoperative evaluation, timing of surgery, and the surgical plan itself.

1.1.6 Pseudoptosis Patients with a large hypotropia, particularly those with a restrictive hypotropia, often present with a concurrent ptosis or pseudoptosis. An infant with a monocular elevator deficiency, for example, may appear to have concurrent, severe ptosis. When the child is made to fixate with the hypotropic eye, the apparent ptosis will resolve if the child can bring the hypotropic eye to the primary position, confirming the diagnosis of pseudoptosis in such cases. On the other hand, correction of the strabismus with surgery is often required to confirm a diagnosis of pseudoptosis if the child cannot bring the eye to the primary position (Chap. 27).

1.3  The Sclera

the palpebral conjunctiva as it relates to strabismus surgery remains ­important. The palpebral conjunctiva begins on the lid margin at the mucocutaneous junction. The conjunctiva is tightly adherent to the underlying tarsus as it progresses into the fornix. The conjunctiva in the fornices is loose and is reflected into several folds, allowing movement of the globe not to be inhibited by connections between the palpebral and bulbar conjunctivae. The upper fornix is typically much deeper than the inferior fornix. A fat pad present in the inferior fornix should be identified and avoided during strabismus surgery (>Fig. 1.6; Chap. 25). Finally, from the fornices, the conjunctiva is reflected upon the globe where it is loosely adherent to the underlying Tenon’s fascia overlying the sclera, finally ending at the limbus. There is some redundancy of the conjunctiva so that excision of small parts of the conjunctiva is well tolerated without altering its function and without significantly reducing its secretory capacity. Only the bulbar conjunctiva is routinely incised during strabismus surgery. Except for a small segment of conjunctiva immediately adjacent to the limbus, Tenon’s fascia will always be found deep to the bulbar conjunctiva. The lateral angle of the conjunctiva is rather nondescript and featureless compared to the medial angle of the conjunctiva. A fold of conjunctiva known as the plica semilunaris conjunctivae (referred to simply as plica here) is present in the medial angle of the conjunctiva and represents a fold in the bulbar conjunctiva. It serves no particular function in the human eye but corresponds to the nictitating membrane of some animal species. When malpositioned or accidentally incised during strabismus surgery, it can produce serious cosmetic and/or functional problems (Chap. 19). Another fold of conjunctiva near the medial canthus forms the caruncle, a transition zone between the conjunctiva and skin. It contains elements of skin and mucous membrane. Small lanugo hairs can often be seen growing out of its head. While the plica is essentially never intentionally incised or surgically altered during strabismus surgery, an incision through the caruncle may occasionally be used in the treatment of complex strabismus, such as the creation of a periosteal flap (Chap. 15) or repair of a lost muscle (Chap. 23).

1.2 The Conjunctiva The conjunctiva is a mucous membrane that covers the posterior surface of the eyelids and the anterior surface of the globe with the exception of the cornea. The bulbar conjunctiva merges with the stroma and epithelium of the cornea. Histologically, the conjunctiva is covered by nonkeratinized stratified squamous epithelial cells and has an underlying substantia propria. The bulbar conjunctiva overlies Tenon’s capsule. The conjunctiva contains numerous mucin-producing goblet cells, particularly in the fornix. The stroma consists of fragile connective tissue that contains lymphoid tissues. Accessory lacrimal glands are found in the conjunctiva of the upper and lower fornix. Though it is a single, continuous membrane, conceptually it is useful to divide the conjunctiva into two parts, namely the palpebral and bulbar conjunctivae. In general, the strabismus surgeon should never enter the palpebral conjunctiva, though an understanding of the anatomy and function of

1.3 The Sclera The sclera is composed of densely packed collagen lamellae. It is continuous with the dura mater of the optic nerve. It also continues across the optic nerve head to form the lamina cribrosa. The sclera is penetrated by a variety of vascular and neural structures anteriorly and posteriorly. The thickness of the sclera also varies with age. It is typically thinnest in a newborn. The thickness of the sclera varies depending on its location on the globe. The sclera is thinnest behind the insertions of the rectus muscles, where its thickness is approximately 0.45 mm [9], a fact that is important to the strabismus surgeon since sutures may need to be passed into this thin sclera to recess a rectus muscle (>Fig. 1.7). The sclera is approximately 0.6–0.7 mm thick at the corneal limbus and 1.1–1.3 mm thick at the posterior pole [9] (>Fig. 1.8).





Surgically Important Anatomy

Chapter 1

Fig. 1.6. Relationship of orbital fat to Tenon’s capsule and other structures. Violation of the posterior portions of Tenon’s capsule can result in intrusion of orbital fat into the surgical space

Fig. 1.7. Thin sclera posterior to the rectus muscle insertions, highlighted area

 

1.4  Fascial System

1.4.2 Function of Tenon’s Capsule and Orbital Connective Tissues

Fig. 1.8. Thickness of the sclera varies depending on its position around the globe

1.4 Fascial System 1.4.1 Tenon’s Fascia The globe is suspended within the bony orbit by a fascial system, the bulk of which is represented by Tenon’s capsule. Tenon’s capsule is a condensation of fibrous tissue that covers the globe from the entrance of the optic nerve into the posterior aspect of the globe extending to within 1 mm of the corneal limbus, where it becomes fused with the overlying conjunctiva. Tenon’s capsule is thick and readily manipulated surgically in young patients, but becomes thin and fragile in older patients. Potential spaces exist both deep and external to Tenon’s capsule, known as the episcleral (sub-Tenon’s space) and the subconjunctival spaces, respectively. We will generally utilize the term episcleral space in this textbook to refer to the potential space deep to Tenon’s capsule. These spaces are important during strabismus surgery as they must be entered in order to gain access to the extraocular muscles. The anterior aspect of Tenon’s capsule is better formed than its posterior aspect. Several large and small structures penetrate Tenon’s capsule including the optic nerve, the extraocular muscles, the vortex veins, and numerous other small neurovascular structures. Strabismus surgery is performed in the episcleral space, on the distal aspect of the extraocular muscles and/or tendons after they have penetrated Tenon’s capsule approximately midway along their lengths. The rectus muscles penetrate Tenon’s capsule to enter the episcleral space posterior to the equator, while the oblique muscles enter the episcleral space anterior to the equator.

Tenon’s capsule and the fascial and ligament system of the orbit are critical to normal control of eye movements. They reduce or check movement of the globe and help to smooth eye movements through their elastic properties, among other functions. Abnormalities of some of these structures, notably the rectus muscle pulleys (see below), have been shown to be associated with anomalous eye movements including some cases of incomitant strabismus [10]. Brown syndrome represents another possible abnormality of the orbital connective tissue structures that may produce unwanted alteration of eye movements. Tenon’s capsule, as with all orbital tissues, should be hand­led with care. Tenon’s capsule acts as a barrier to orbital fat, and violation of the posterior aspects of the capsule can result in unwanted intrusion of orbital fat into the surgical space (>Fig. 1.6). This surgical complication can cause significant difficulties in completing planned surgery and can also lead to fat adherence and restrictive strabismus postoperatively (Chap. 25). The strabismus surgeon must become very familiar with Tenon’s capsule, as it must be manipulated during all strabismus operations. The extraocular muscles penetrate Tenon’s capsule to enter the episcleral space, coursing toward their insertions into the sclera (>Fig. 1.9). Thus it is in the episcleral space, containing a length of about 7–10 mm of the rectus muscles, where the majority of extraocular muscle surgery is performed. After entering the episcleral space, the muscles have no sheath, but instead are covered by episcleral connective tissues that are loosely fused with the muscle. This tissue expands laterally along the edges of the muscles to form the intermuscular membrane and is present all the way to the muscle insertion. These tissues fuse with Tenon’s capsule posteriorly where the muscles penetrate Tenon’s capsule. The orbital aspect of the sheath of the superior rectus muscle is closely adherent to the internal surface of the sheath of the levator palpebrae superioris muscle of the upper eyelid. The close association of these two muscles through their fascial sheaths accounts, in part, for the cooperative action seen during contraction of these two muscles, such as depression of the upper eyelid with downward gaze. The surgeon must be aware of these connections because they can have important implications for the patient following strabismus surgery on the vertical rectus muscles (Chap. 26). The global portion of the sheath is tenuously associated with the sheath of the superior oblique tendon (>Fig. 1.10). The fascial sheath surrounding the inferior rectus muscle is complex. It tends to be thicker and more readily apparent than the fascial sheath surrounding the other rectus muscles, and this is readily apparent during surgery. The global portion of this sheath fuses with and becomes continuous with Tenon’s capsule, while the orbital portion contributes to the formation of Lockwood’s ligament of the lower eyelid, helping to explain why surgery on the inferior rectus muscle can alter the position of the lower eyelid (Chap. 26). The fascial sheath surrounding the portion of the superior oblique tendon distal to the trochlea is both strong and thick.



10

Surgically Important Anatomy

Chapter 1

Fig. 1.9. Diagrammatic representation of Tenon’s capsule and relationship to the extraocular muscles. Note that the rectus muscles are located external to Tenon’s capsule posteriorly. They penetrate Tenon’s capsule to enter the episcleral space, then course anteriorly to insert on the sclera. The inferior oblique muscle and superior oblique tendon enter the episcleral space anteriorly and course posteriorly to insert on the sclera. The rectus muscle pulleys, muscle capsule, and intermuscular septum are not represented in this diagram

Fig. 1.10. Complex sheath of the superior oblique tendon. Note tenuous attachments to the sheath of the superior rectus muscle and to the levator muscle of the upper eyelid

The potential space inside the superior oblique tendon sheath is continuous with the episcleral space. Numerous attachments extend from the sheath to adjacent structures including attachments to the global aspect of the sheath of the superior rectus muscle and attachments to the sheath of the levator palpebrae superioris muscle of the upper eyelid (>Fig. 1.10). Abnormalities involving this sheath often play a role in the etiology of Brown syndrome. The fascial sheath of the inferior oblique muscle surrounds the muscle from its origin to insertion. It becomes thicker as the muscle approaches its insertion and it is usually tightly adherent to the orbital aspect of the sheath of the inferior rectus muscle. Small extensions of the sheath near the inferior oblique muscle insertion are directed to the sheath of the lateral rectus muscle and to the sheath surrounding the optic nerve posteriorly.

the capsule at this position in the orbit. Fibroelastic sleeves consisting of dense bands of collagen, elastin, and smooth muscle surround the rectus muscles. These sleeves are suspended from the orbit and adjacent extraocular muscle sleeves by bands of tissue having similar composition. Often referred to as check ligaments, these sleeves and their connections to the orbital walls have a significantly more complex function than simply to “check” movement of the globe and the term check ligaments should probably be discarded. Condensations and extensions from these muscle sheaths ultimately are associated with connections anteriorly as well. Some consider all of these structures collectively as Tenon’s capsule [11] though for practical purposes while they may all be continuous, with one blending gradually into the other, the rectus muscle pulleys are so specialized in function that they should be considered separate from Tenon’s capsule. High-resolution computed tomography and magnetic resonance imaging have demonstrated that the paths of the rectus muscles remain stable relative to their adjacent orbital walls throughout most of their course in the orbit, even during eye movements and following large surgical transposition procedures [12, 13]. Only the anterior aspect of the muscles actually moves during normal eye movements into secondary gaze

1.5 The Rectus Muscle Pulley System A reflection extending from Tenon’s capsule envelops the posterior portion of the extraocular muscles that are extrinsic to

 

1.5 The Rectus Muscle Pulley System

positions, while the posterior aspects of the rectus muscles are relatively fixed in position by rectus muscle pulleys which are in part located near the equator of the globe. The rectus muscle pulleys essentially function as the effective origins of the rectus muscles [14] (>Fig. 1.11). These muscle sleeves are continuous with Tenon’s capsule anteriorly and posteriorly. The pulleys are important for altering both the paths of the rectus muscles through the orbit and their function. These sleeves are located near the equator of the globe and are approximately 13–19 mm in anterior–posterior dimension [13]. During muscle contraction, the sleeves act as pulleys, restraining the rectus muscles paths and re-directing

the force of contraction toward the globe. The orbital layer of the rectus extraocular muscles has been demonstrated to insert into the corresponding rectus muscle pulley, rather than on the globe [15]. The active-pulley hypothesis proposed by Demer and coworkers [15] suggests that the global layer of each rectus extraocular muscle rotates the globe while the orbital layer of the muscle inserts on its respective pulley and influences the rotational axis of the rectus muscle through changes in the position of the pulley during movements of the globe (>Fig. 1.11c). This arrangement is believed to provide a mechanical explanation of important aspects of eye movements including Listing’s law [15, 16].

Fig. 1.11a–c. Rectus muscle pulleys. a Schematic of rectus muscle pulleys. (GL Global layer, IO inferior oblique, IR inferior rectus, LE lateral enthesis, LG lacrimal gland, LPS levator palpebrae superioris, LR lat-

eral rectus, ME medial enthesis, MR medial rectus, OL orbital layer, SO superior oblique, SR superior rectus)

11

12

Surgically Important Anatomy

Chapter 1 Fig. 1.11a–c. (continued) Rectus muscle pulleys. b Magnetic resonance imaging demonstrating position of pulley for medial rectus muscle. c Change in pulley position that occurs during muscle contraction. {a With permission from Demer JL (2006) Current concepts of mechanical and neural factors in ocular motility. Curr Opin Neurol 19: 4–13; copyright 2006 Lippincott Williams and Wilkins [16]; b and c courtesy of Joseph L Demer, MD; NIH grant EY08313}W

1.6 Gross Anatomy of the Extraocular Muscles 1.6.1 Rectus Muscles Each of the four rectus muscles originates in the posterior orbit at the annulus of the Zinn surrounding the optic canal and the inferior portion of the superior orbital fissure. Fascial attachments between the origins of the medial and superior rectus muscles into the dura covering the optic nerve are thought to be the cause of pain with eye movements in patients with acute optic neuritis. The origin of the lateral rectus muscle has a superior and inferior head that are located on opposite sides of the superior orbital fissure [17]. For practical purposes, the rectus muscles can be considered to be approximately 40 mm in length in an adult. Coursing anteriorly from the annulus of Zinn, the medial, lateral, and inferior rectus muscles follow the course of adjacent orbital walls for a good portion of their length, while the superior rectus muscle is separated from the orbital roof by the levator palpebrae superioris muscle of the upper eyelid. The paths of the rectus muscles in the orbit curve sharply toward the globe starting approximately 7–10 mm from the equator as the connective tissue/muscular pulleys described above alter their paths. The thin rectus muscles eventually penetrate Tenon’s capsule 7–10 mm from their insertions into the

sclera. After entering the episcleral space and coursing further anteriorly, each eventually becomes tendinous, ultimately inserting into the sclera as a tendon posterior to the limbus. The tendinous insertions of each of the rectus muscles are roughly 10–11 mm in width [18] (>Table 1.1). The average distance of each rectus muscle insertion from the limbus is shown in Table 1.1 and Fig. 1.12, along with other key anatomical features. The medial rectus muscle insertion is typically located closest to the limbus, followed by the inferior rectus, lateral rectus, and finally the superior rectus muscle, which is typically inserted furthest from the limbus. The insertions, particularly those of the vertical rectus muscles, are curved with their convexity away from the limbus. The temporal corners of the vertical rectus muscles are further from the limbus than are the nasal corners. Variations from the means shown are common. A circular line connecting the center of the rectus muscle insertions is known as the spiral of Tillaux (>Fig. 1.13). The spiral of Tillaux has several important implications: (1) helping the surgeon to remain oriented during surgery, and helping to assure surgery is performed on the correct muscle, (2) providing some insight as to the amount and type of previous strabismus surgery performed during reoperations, and (3) providing landmarks to help guide reinsertion of transposed and advanced muscles. It is not uncommon for small bundles of muscle fibers to be re-directed posteriorly near the insertion to insert several millimeters behind the remainder of the rectus muscle insertions (>Fig. 1.14). These

 

Fig. 1.12. Important measurements of rectus muscle dimensions. Average width of rectus muscle insertions, distance of insertion to the corneal limbus and length of tendon, in adults. (With permission from

1.6  Gross Anatomy of the Extraocular Muscles

Apt L. An anatomical reevaluation of rectus muscle insertions. Trans Am Ophthalmol Soc 1980;78:365–375 [18])

Table 1.1. Important measurements of rectus muscle dimensions. Average width of rectus muscle insertions in an adult [18], distance of insertion to the corneal limbus [18], and length of tendon [26] Muscle

Rectus muscle tendon dimensions Distance from limbus (mm)

Width (mm)

Length (mm)

Medial rectus

5.3

11.3

4

Inferior rectus

6.8

10.5

4.2

Lateral rectus

6.9

10.1

6.65

Superior rectus

7.9

11.5

5

Fig. 1.13. The spiral of Tillaux

13

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Surgically Important Anatomy

Chapter 1 Fig. 1.14. Muscle “footplates” (left of asterisk) representing muscle bundles redirected posterior to the insertion are common and are probably of no functional significance

Fig. 1.15. Identifying the rectus muscle insertions by visualizing their anterior ciliary vessels beneath the conjunctiva as the eye is rotated. Note movement of the anterior ciliary vessels relative to the conjunctival vessels

Fig. 1.16. Palpation of a rectus muscle border. After visual identification of the insertion, a hook is placed adjacent to the muscle border (top left). While depressing the hook toward the globe, the hook is moved toward the muscle (top right). The muscle can be seen to bunch against the hook as it is advanced (bottom)

 

so-called muscle footplates, once thought to have considerable importance in the etiology of strabismus [19], appear today to be of little functional significance. The insertions of the rectus muscles can be easily seen through intact conjunctiva. Their locations are often first recognized by visualizing their associated anterior ciliary vessels as they course onto the episclera anterior to the rectus muscle insertions. These vessels are most readily identified as the eye is rotated to and fro at right angles to the path of the muscle (>Fig. 1.15) where they can be seen to move with globe rotation asynchronously from the overlying conjunctival vessels. Once identified, the muscles themselves can usually be seen as slightly darkened and slightly raised structures beneath the conjunctiva. We find the technique of rectus muscle palpation with a blunt instrument to be highly useful when identifying the borders of the rectus muscles intraoperatively, and often find the palpation technique more valuable than visual inspection. To perform this technique, the eye is rotated with fixation forceps or bridle sutures into the desired position for surgery (>Fig. 1.16). A blunt instrument, such as a muscle hook, is placed on the conjunctiva between two adjacent rectus muscles approximately 10 mm posterior to the corneal limbus. While applying gentle posterior pressure on the globe with the muscle hook, the hook is directed toward the rectus muscle. The border of the muscle can be easily palpated in this manner and readily visualized as the hook makes contact with the border of the muscle, assuring the surgeon that the eye has been properly positioned for surgery and helping to facilitate accurate placement of the conjunctival incision.

1.7 Innervation of the Extraocular Muscles The third cranial nerve (oculomotor nerve) is the most complex of the cranial nerves supplying innervation to the extraocular muscles. It provides the innervation to four of the six extraocular muscles and to the levator palpebrae superioris muscle of the upper eyelid. The inferior division of the third nerve supplies the medial and inferior rectus muscles as well as the inferior oblique muscle. The superior division supplies the superior rectus muscle and levator palpebrae superioris muscle of the upper eyelid. Motor branches of the third nerve enter the medial and inferior rectus muscles at approximately the junction between the posterior one-third and anterior two-thirds of the muscle from the internal or global surface of the muscle. The neurovascular bundle supplying the inferior oblique muscle enters the muscle from its posterior surface near the lateral border of the inferior rectus muscle [20]. The superior oblique muscle is innervated by the fourth cranial nerve (trochlear nerve). It is the only extraocular muscle that receives its innervation from the external or orbital surface of the muscle. The nerve passes superiorly from the medial side of the superior oblique muscle to the orbital side of the muscle prior to entering the muscle as several small branches. The lateral rectus muscle is innervated by the sixth cranial nerve (abducens nerve). The muscle is innervated from the in-

1.8  Blood Supply to Extraocular Muscles

ternal or bulbar surface of the muscle near the junction of the anterior two-thirds and posterior one-third of the muscle.

1.8 Blood Supply to Extraocular Muscles Each of the extraocular muscles receives its blood supply from the medial and lateral muscular branches of the ophthalmic artery. The medial branch supplies the inferior and medial rectus muscles as well as the inferior oblique muscle, while the lateral branch supplies the lateral and superior rectus muscles, the superior oblique muscle, and the levator muscle of the upper eyelid. The inferior rectus muscle and inferior oblique muscle also receive a small contribution of blood supply from other sources. The arteries of the four rectus muscles enter the muscles on their global surfaces at approximately the junction between the anterior two-thirds and posterior third of the muscle. They course anteriorly, emerging onto the orbital surface of the muscle/tendon approximately 10–12 mm from the insertions of the tendons into the sclera, where they are known as the anterior ciliary arteries. Each rectus muscle characteristically has two anterior ciliary arteries, except for the lateral rectus muscles, which characteristically have only one (>Fig. 1.17). The course of the anterior ciliary arteries along the muscles and their tendons is highly variable and this variation is important to recognize when planning surgery on patients who are at risk for anterior segment ischemia (Chap. 20). The anterior ciliary vessels course forward to the episclera, where they supply branches to the sclera, limbus and to the conjunctiva. They enter the sclera near the limbus where they ultimately anastomose with the long ciliary arteries to form the major arterial circle of the iris. Veins corresponding to the muscle’s arteries drain into the superior and inferior orbital veins.

Fig. 1.17. The anterior ciliary arteries. Except for the lateral rectus muscle, each rectus muscle contains two anterior ciliary arteries

15

16

Surgically Important Anatomy

1.9 Surgically Important Anatomy of Individual Extraocular Muscles This section will review key elements of the surgical anatomy of the individual extraocular muscles and surrounding tissues that the strabismus surgeon is likely to encounter frequently during standard strabismus surgery. Information about the basic anatomy, function, and structure of each extraocular muscle and its supporting fascia is found elsewhere in this and subsequent chapters.

1.9.1 Medial Rectus Muscle The medial rectus muscle insertion is typically closer to the corneal limbus than that of the other rectus muscles. According to Apt [18] in the adult eye, the mean insertion distance from the center of the insertion to the anterior limbus is 5.3 mm (>Fig. 1.12). There is a wide range in variation of this distance [18] and this distance is smaller in a child. As a general rule of thumb, the surgeon should expect to find the insertion 1 mm closer to the limbus than the values shown in Table 1.1 for a child between the ages of 6 and 12 months. Helveston believes that variation in the insertion of the medial rectus muscle tendon relative to the limbus is large and common, suggesting a range of 3.5–6 mm from the corneal limbus [21]. He believes that the large variation in distance of the insertion of the medial rectus muscle relative to the corneal limbus makes the muscle insertion a poor landmark for measuring during recession surgery on the medial rectus muscle and prefers to utilize the limbus as the landmark, rather than the muscle insertion. The medial rectus muscle is the only extraocular muscle that does not have a direct attachment to one of the other extraocular muscles. This increases the likelihood that the medial rectus muscle will retract posteriorly into the orbit if extensive dissection of the medial rectus muscle fascial system is carried out and the surgeon loses control of the muscle after it has been detached from the sclera. The surgeon is not likely to engage other vascular or muscular structures when hooking the medial rectus muscle. The sclera posterior to the rectus muscle insertions is thinner than the sclera anterior to the rectus muscle insertions. This is particularly true of the region posterior to the medial rectus muscle insertion. Small recessions may require fixation of the muscle to this very thin portion of the sclera, where the risk of scleral perforation is probably higher, and may warrant consideration of a muscle hang-back procedure from the thicker sclera at the insertion in some situations. The underlying uvea can sometimes be seen through the thin sclera posterior to the media rectus muscle insertion and can occasionally be a cause of significant concern to patients postoperatively (Chap. 19). The conjunctival anatomy of the medial aspect of the eye is more complex than the conjunctiva encountered when performing surgery on the other rectus muscles (>Fig. 1.18). Care must be taken during the creation of conjunctival incisions at

Chapter 1

the start of surgery and during closure of conjunctival incisions at the conclusion of surgery to avoid disruption of the key anatomical landmarks of the medial conjunctiva, which can result in very significant cosmetic and functional complications (Chap. 19).

1.9.2 Lateral Rectus Muscle Surgery on the rectus muscle would be straightforward but for two anatomical issues. First, the tendon of the lateral rectus muscle is both thin and long. This makes the tendon more prone to being split with a muscle hook as the muscle is being isolated and it makes passage of a suture to secure the muscle insertion more difficult. In addition to having a tendon that is longer and thinner than those of the other rectus muscles, the lateral rectus muscle typically has only a single anterior ciliary artery. These features can be helpful in confirming that the correct muscle has been isolated if the surgeon becomes disoriented during surgery. Second, the inferior oblique muscle inserts into the sclera approximately 10 mm posterior to the limbus beneath the inferior aspect of the lateral rectus muscle. Loose attachments between the fascial sheaths of these two muscles are usually present. The inferior oblique muscle is often inadvertently hooked along with the lateral rectus muscle when isolation of the lateral rectus muscle is attempted. This can occur during attempts to isolate the lateral rectus muscle from its superior or inferior border, but is more likely to occur when attempting to isolate the lateral rectus muscle from its inferior border. This complication is more likely to occur when the lateral rectus muscle has been previously recessed. The inferior oblique muscle can occasionally be isolated instead of the lateral rectus muscle when attempting to isolate the muscle from its inferior border. This is more likely to occur in eyes with previous surgery and an extensive amount of scarring. Failure to recognize that the inferior oblique muscle has been inadvertently hooked can result in a significant postoperative motility disturbance that is of a restrictive nature [22] (Chap. 25).

Fig. 1.18. Important conjunctival landmarks

 

1.9.3 Inferior Rectus Muscle Surgery on the inferior rectus muscle would be rather straightforward if not for the presence of a number of important surrounding structures. The midpoint of the insertion inserts an average of 6.8 mm posterior to the anterior limbus [18] (>Fig. 1.12). The temporal border of the tendon inserts approximately 2.5 mm more posteriorly than the nasal border of the insertion [18], a fact which should be considered when recessing or resecting the muscle. When hooking the inferior rectus muscle, the surgeon should avoid passing the hook too deeply into the orbit. A vortex vein can typically be seen posteriorly near both the medial and lateral borders of the inferior rectus muscle (>Fig. 1.19). Disturbance of a vortex vein can result in considerable bleeding, rendering continuation of surgery hazardous (Chap. 24). The fascial sheath of the inferior rectus muscle is typically thicker than that associated with the other rectus muscles. The inferior rectus muscle is intimately associated with the inferior oblique muscle and Lockwood’s ligament through these fascial attachments. The orbital aspect of the fascial sheath of the inferior rectus muscle forms part of Lockwood’s ligament. Because of these firm attachments to Lockwood’s ligament, large recessions or resections of the inferior rectus muscle can produce unwanted retraction and advancement of the lower eyelid, respectively. Techniques to minimize these undesired changes in eyelid position are reviewed in Chap. 26. Many surgeons more generously dissect the fascial attachment associated with the inferior rectus muscle to minimize changes in eyelid position. Intrusion into a large fat pad that is closely associated with the inferior rectus muscle can occur during dissection of these fascial tissues.

Fig. 1.19. Vortex veins as seen from the posterior aspect of the globe

1.9  Anatomy of Individual Extraocular Muscles

The firm attachments of the inferior rectus muscle to Lockwood’s ligament and to the inferior oblique muscle, which crosses inferior to the inferior rectus muscle, limit the tendency of the inferior rectus muscle to retract into the posterior orbit when detached from the sclera. These attachments are invaluable in helping to identify a lost or traumatically detached inferior rectus muscle (Chap. 23).

1.9.4 Superior Rectus Muscle Surgery on the superior rectus muscle is complicated by the presence of adjacent vascular, muscular, and tendinous structures. If a fornix conjunctival incision is planned to surgically access the muscle, it is generally placed in the superotemporal quadrant, to avoid disturbing the superior oblique tendon and its trochlea. The central portion of the tendon of the superior rectus muscle inserts approximately 7.9 mm from the anterior corneal limbus. The insertion is curved relative to the limbus. The temporal border of the tendon inserts almost 3 mm more posteriorly than the nasal border [18], a fact which should be considered when recessing or resecting the muscle. It is the only rectus extraocular muscle that inserts posterior to the ora serrata. As such, a perforation of the eye wall near the insertion of the superior rectus muscle may enter the retina. A vortex vein can usually be found posteriorly near the border of the superior rectus muscle nasally and temporally. Vortex veins are infrequently damaged during surgery on the superior rectus muscle. Compared to the inferiorly located vortex veins, they are more difficult to inadvertently hook or otherwise manipulate when attempting to isolate the superior rectus muscle because they are somewhat protected by the superior oblique tendon. The fascial sheath surrounding the superior rectus muscle is thicker on its orbital surface. Here, there are relatively firm attachments between the sheath of the superior rectus muscle and the sheath of the levator muscle of the upper eyelid. ­These firm attachments between the superior rectus and levator muscles are in large part responsible for upper eyelid retraction and advancement following superior rectus muscle recession and resection, respectively (Chap. 26). These unwanted alterations of upper eyelid position are most likely to occur with recessions or resections of greater than 5 mm. The global aspect of the muscle sheath of the superior rectus muscle is attached to the superior oblique tendon through relatively tenuous connections (>Fig. 1.20). If the close relationship between these two structures is not recognized, the superior oblique tendon can sometimes be inadvertently hooked, along with the superior rectus muscle tendon. If unrecognized, the superior oblique tendon may be sutured along with the superior rectus tendon and recessed or resected, producing unexpected torsional and vertical misalignment following surgery. Because the insertion of the superior rectus muscle is relatively far from the limbus, there is a tendency to pass the initial muscle hook more posteriorly when attempting to isolate the muscle insertion. This increases the risk of capturing a portion of the superior oblique tendon at the same time. We recommend that the strabismus

17

18

Surgically Important Anatomy

surgeon who may be less accustom to operating on the superior rectus muscle inspect the insertion site once the muscle is isolated to make certain that the superior oblique tendon is not engaged on the hook.

1.9.5 Superior Oblique Muscle/Tendon Compared to the frequency of surgery on the other extraocular muscles, surgery is performed relatively infrequently on the superior oblique. Only the tendinous portion of the superior oblique, that portion distal to the trochlea, is manipulated surgically. The tendon runs posteriorly and temporally from the trochlea, which is located in the anteromedial orbit, to insert well behind the equator of the globe. The tendon travels inferior to the superior rectus muscle, crossing under the superior rectus muscle beginning 5–10 mm posterior to the insertion of the superior rectus muscle into the sclera. Adhesions between the sheath of the superior oblique tendon and the sheath of the superior rectus muscle often must be severed to complete surgery on the superior oblique tendon. The capsule of the tendon is continuous with the episcleral space at its insertion and is continuous with Tenon’s capsule surrounds the tendon (>Fig. 1.10). During surgery, this capsule should be disturbed as little as possible. This is especially true of surgery performed to insert a superior oblique tendon expander [23]. Disruption of the capsule surrounding the superior oblique tendon is a potential cause of secondary restrictive strabismus following superior oblique tendon expander surgery (Chap. 25). The anterior portion of the superior oblique tendon insertion may underlie the superior rectus muscle temporally. The thin tendinous insertion is broad and the most posterior por-

Fig. 1.20. Fine attachments between the sheath of the superior rectus muscle and the sheath of the superior oblique tendon

Chapter 1

tion of the tendon lies only 8–10 mm from the sheath of the optic nerve. The thinness, width, and posterior nature of the insertion of the superior oblique tendon combine to make surgical isolation of the tendon difficult (>Fig. 1.20). The tendon is easily split with a muscle hook, and isolation of only a portion of the superior oblique tendon can easily occur. If unrecognized, the surgical procedure may have a minimal and/or unpredictable effect on ocular alignment. While it is optimal to isolate the superior oblique tendon under direct visualization, it is often not possible to clearly visualize the more posterior fibers of the tendon during this process. After hooking the tendon, the proximal fibers can be visually inspected to assure that there is not a bundle of remaining tendinous fibers running posteriorly toward the insertion, having been excluded from the hook. Superior oblique traction testing (Chap. 8) can also be useful in confirming that the entire superior oblique tendon has been surgically disinserted. The posterior edge of the superior oblique tendon insertion lies between and slightly anterior to two vortex veins (>Fig. 1.19). These vortex veins, particularly the temporal one, can be easily damaged during surgery on the superior oblique tendon.

1.9.6 Inferior Oblique Muscle Surgery on the inferior oblique muscle is generally conducted in the inferotemporal quadrant, though some recently described procedures involve manipulation of the muscle in the inferonasal quadrant [24]. The inferior oblique muscle is the only extraocular muscle that does not have a tendinous portion distally. The muscular insertion of the inferior oblique is located temporally beneath the inferior border of the lateral

Fig. 1.21. Insertion of the inferior oblique muscle under the lateral rectus muscle

 

rectus muscle. A dual insertion is said to be present in almost 11% of inferior oblique muscles [25]. Failure to recognize a dual insertion can result in minimal and/or unpredictable effects on ocular alignment following surgery. The capsule of the inferior oblique muscle is relatively thick and fine attachments between its capsule and that of the lateral rectus muscle are generally present near the insertion of the inferior oblique muscle (>Fig. 1.21). A large orbital fat pad in the inferotemporal quadrant of the orbit can be easily disturbed during surgery on the inferior oblique muscle. This usually occurs during the isolation and dissection of the belly of the inferior oblique muscle, and can result in intraoperative bleeding and intrusion of orbital fat into the operative field, both of which can hinder the visualization necessary to complete surgery and can result in the development of a restrictive strabismus postoperatively. The inferior oblique muscle is usually identified surgically as it courses across the inferotemporal quadrant, approximately 15 mm from the limbus. Unlike the other extraocular muscles, it is not surgically identified in its resting position on the globe, but rather is retracted inferiorly and identified as it courses within Tenon’s capsule (>Fig. 1.22). The muscle is isolated by passing a hook posterior to the belly of the muscle and retracting the muscle anteriorly. It is during this process, that the surgeon is most likely to encounter surrounding orbital fat and may encounter a vortex vein located in the inferotemporal quadrant near the lateral border of the inferior rectus muscle. These complications can be minimized by attention to careful surgical technique as reviewed in Chap. 11. We recommend that the surgeon directly visualizes the posterior border of the inferior oblique muscle and the nearby vortex vein prior to attempting to isolate the muscle on a hook. The effective insertion of the inferior oblique muscle is not at the medial orbital wall where the anatomical insertion is lo-

References

cated, but instead is at the neurovascular bundle which enters the inferior oblique muscle near the temporal border of the inferior rectus muscle [20]. The neurovascular bundle is usually not visualized or disturbed during standard surgery on the inferior oblique muscle. An exception is denervation and extirpation of the inferior oblique muscle, which requires transection of the neurovascular bundle (Chap. 11). This bundle is generally best palpated with a hemostat, a maneuver that facilitates its visual identification.

References 1.

2.

3. 4. 5.

6.

Paysse EA, Khokhar A, McCreery KM, Morris MC, Coats DK (2002) Up-slanting palpebral fissures and oblique astigmatism associated with A-pattern strabismus and overdepression in adduction in spina bifida. J AAPOS 6:354–659 Coats DK, Paysse EA, Stager DR (2000) Surgical management of V-pattern strabismus and oblique dysfunction in craniofacial dysostosis. J AAPOS 4:338–342 Parks MM (1958) Isolated cyclovertical muscle palsy. AMA Arch Ophthalmol 60:1027–1035 Wilson ME, Hoxie J (1993) Facial asymmetry in superior oblique muscle palsy. J Pediatr Ophthalmol Strabismus 30:315–318 Paysee EA, Coats DK, Plager DA (1995) Facial asymmetry and tendon laxity in superior oblique palsy. J Pediatr Ophthalmol Strabismus 32:158–161 Velez FG, Clark RA, Demer JL (2000) Facial asymmetry in superior oblique muscle palsy and pulley heterotopy. J AAPOS 4:233–239

Fig. 1.22. Identification of the inferior oblique muscle (arrow) in Tenon’s fascia as it is retracted inferiorly. Note the presence of a vortex vein (asterisk) near the posterior border of the muscle

19

20

Surgically Important Anatomy 7.

8.

9. 10.

11. 12.

13.

14.

15.

16.

Helveston EM, Krach D, Plager DA, Ellis FD (1992) A new classification of superior oblique palsy based on congenital variations in the tendon. Ophthalmology 99:1609–1615 Bagolini B, Campos EC, Chiesi C (1982) Plagiocephaly causing superior oblique deficiency and ocular torticollis. A new clinical entity. Arch Ophthalmol 100:1093–1096 Apple DJ, Rabb MF (1985) Ocular pathology. Clinical applications and self-assessment, 3rd edn. Mosby, St. Louis, Mo. Oh SY, Clark RA, Velez F, Rosenbaum AL, Demer JL (2002) Incomitant strabismus associated with instability of rectus pulleys. Invest Ophthalmol Vis Sci 43:2169–2178 Roth A, Muhlendyck H, De Gottrau P (2002) [The function of Tenon’s capsule revisited.] J Fr Ophtalmol 25:968–976 Clark RA, Rosenbaum AL, Demer JL (1999) Magnetic resonance imaging after surgical transposition defines the anteroposterior location of the rectus muscle pulleys. J AAPOS 3:9–14 Demer JL, Miller JM, Poukens V (1996) Surgical implications of the rectus extraocular muscle pulleys. J Pediatr Ophthalmol Strabismus 33:208–218 Demer JL, Miller JM, Poukens V, Vinters HV, Glasgow BJ (1995) Evidence for fibromuscular pulleys of the recti extraocular muscles. Invest Ophthalmol Vis Sci 36:1125–1136 Demer JL, Oh SY, Poukens V (2000) Evidence for active control of rectus extraocular muscle pulleys. Invest Ophthalmol Vis Sci 41:1280–1290 Demer JL (2006) Current concepts of mechanical and neural factors in ocular motility. Curr Opin Neurol 19:4–13

Chapter 1 17. Sevel D (1986) The origins and insertions of the extraocular muscles: development, histologic features, and clinical significance. Trans Am Ophthalmol Soc 84:488–526 18. Apt L (1980) An anatomical reevaluation of rectus muscle insertions. Trans Am Ophthalmol Soc 78:365–375 19. Scobee RC (1948) Anatomic factors in the etiology of strabismus. Am J Ophthalmol 31:781 20. Stager DR, Weakley DR Jr., Stager D (1992) Anterior transposition of the inferior oblique. Anatomic assessment of the neurovascular bundle. Arch Ophthalmol 110:360–362 21. Helveston EM (1993) Surgical management of strabismus. An atlas of strabismus surgery, 4th edn. Mosby, St. Louis, Mo. 22. Helveston EM, Alcorn DM, Ellis FD (1988) Inferior oblique inclusion after lateral rectus surgery. Graefes Arch Clin Exp Ophthalmol 226:102–105 23. Wright KW (1991) Superior oblique silicone expander for Brown syndrome and superior oblique overaction. J Pediatr Ophthalmol Strabismus 28:101–107 24. Stager DR Jr., Wang X, Stager DR Sr., Beauchamp GR, Felius J (2004) Nasal myectomy of the inferior oblique muscles for recurrent elevation in adduction. J AAPOS 8:462–465 25. Deangelis DD, Kraft SP (2001) The double-bellied inferior oblique muscle: clinical correlates. J AAPOS 5:76–81 26. Duke-Elder S (1973) Ocular motility and strabismus. In: Duke-Elder S (ed) System of ophthalmology. Mosby, St. Louis, Mo., p 8

Chapter

Physiology of Eye Movements

2

2 Kinematics is the science concerned with movements of the parts of the body. All movement potentially possible for the globe can be broken down into a combination of one or more of six elements. These include the three translatory movements and three rotary movements. Translatory movements of the globe may be left or right, up or down, and anterior or posterior. The center of the globe must shift during translatory movements. Rotary movements of the globe can occur around a vertical, a horizontal, and an anteroposterior axis. The center of the globe does not shift position during a pure rotary movement. While technically possible for a globe to undergo all of these movements, the translatory movements are small and can be ignored when discussing the basic physiology of ocular movements. The primary and secondary actions of each of the extraocular muscles refer to major and minor actions of individual extraocular muscles when the muscles act on the globe from the primary position. There is a fixed muscle plane for each of the extraocular muscles that passes through the center of rotation of the globe and runs along the direction of the muscle from its origin (or functional origin) to its insertion into the sclera, when the muscles are operating on the globe while it is in the primary position. In other positions of gaze, these muscle planes change and movements of the globe that result from mus­cle contraction in other gaze positions are altered compared to movements from the primary position. For example, the superior oblique muscle functions primarily to produce incyclorotation from the primary position, but depression becomes its primary function when the globe is adducted. The functions of each of the extraocular muscles from the primary position can readily be determined by analysis of the muscle planes relative to the globe with reference to three major axes of rotation as described below. The surgeon need only understand the relative positions of the effective origin and insertion in relation to these axes to understand the functions of each of the extraocular muscles acting on the globe in the primary position and in other gaze positions. In the discussion that follows, several assumptions are made. The eyes are considered to be fixating on a distant target and oriented in the primary position at the initiation of the movement, unless otherwise stated. Movements are assumed to occur around a fixed center of rotation of the globe and the muscles pairs in each eye are considered to have identical muscle planes relative to the major axes of rotation of the globes. It should be noted, however, that small translatory

movements of the globe do occur and the muscle planes of the muscle pairs are slightly askew. While these assumptions are not technically accurate, they are sufficient to serve as a basis of reference for discussion of ocular movements.

2.1 Axes of Ocular Rotation and Listing’s Plane From a practical standpoint, the center of rotation of the eye is stable, and small translatory movements of the globe can be ignored when considering the physiology of normal eye movements. While technically small changes in the center of rotation of the eye can and do occur, we will consider each eye to have only three axes of rotation, all passing through this “center of rotation” (>Fig. 2.1). The three major reference axes of the

Fig. 2.1. Reference axes of rotation of the globe and Listing’s plane. Note that the x-axis and the z-axis are in Listing’s plane and that the y-axis is perpendicular to Listing’s plane

22

Physiology of Eye Movements

eye were designated the y-axis, x-axis, and z-axis, respectively, by Fick in 1854. The y-axis is the anteroposterior axis and coincides with the line of fixation. The median plane of the globe is oriented along the y-axis. The two remaining axes of rotation are perpendicular to the y-axis. The horizontal axis is known as the x-axis and the vertical axis is known as the z-axis. The horizontal and vertical axes of rotation are assumed to lie in Listing’s plane. Listing’s plane is a fixed plane in the orbit that passes through the center of rotation of the globe containing these two major axes of rotation. Listing’s plane is considered to pass through the equator of the globe.

2.2 Duction Movements Duction movements are excursions of an individual globe. Excursions around the vertical axis (z-axis) represent horizontal eye movements and include adduction, a nasal movement, and abduction, a temporal movement. Rotations around the horizontal axis (x-axis) represent vertical eye movements. Elevation or sursumduction represents an upward movement of the eye while depression or deorsumduction represents downward movement of the eye. Combinations of horizontal and vertical excursions produce movement of the globe into oblique positions of gaze. The axes of rotation of oblique movements also lie in the equatorial or Listing’s plane. Ocular excursions also occur around the y-axis, though they are more difficult to appreciate clinically. Rotations of an eye around the y-axis are known as cycloductions. Rotation of the 12 o’clock meridian nasally represents incycloduction, ­while rotation of the 12 o’clock meridian temporally is referred to as excycloduction.

Chapter 2

converge if the fovea of each eye is to maintain fixation on the object of interest. Vertical vergence and cyclovergence also occur, typically as involuntary movements to spontaneously correct vertical heterophorias and cyclophorias, respectively.

2.5 Basic Laws Governing Eye Movements The eyes function together as a pair based on several fundamental laws of ocular motility. The key laws of ocular motility that are most important clinically include Sherrington’s law of reciprocal innervation and Herring’s law of equal innervation. Contraction of an eye muscle produces movement of the globe. The muscle that produced the movement is known as the ago­ nist. The antagonist produces a movement in the opposite direction. For example, the medial rectus muscle adducts the globe while the lateral rectus muscle abducts the globe. Thus the two muscles are antagonists relative to each other. Muscles which move the globe in the same direction are know as synergists. For example, the superior rectus muscle and the inferior oblique muscle both elevate the globe and there­fore are synergists with respect to elevation. They are antagonists, however, with respect to cyclorotations of the globe. The inferior oblique muscle produces excyclorotation, while the superior rectus muscle produces incyclorotation. Muscles in each eye, which move the two eyes in the same direction, are also synergistic and are known as yoke muscles (>Fig. 2.2). The medial rectus muscle of the right eye and the lateral rectus of the left eye both function to move the eyes to the left (levoversion), and thus are yoke muscles. Muscle pairs in the two eyes are also yoked in this fashion. For example, the inferior oblique muscle and superior rectus muscle (both of which elevate the eyes) of one eye are yoked with these same elevators of the opposite eye.

2.3 Version Movements Version movements are simultaneous movements of the two eyes in the same direction. Version movements function to expand the field of view and to direct the fovea of each eye to the object of attention. Versions can be both voluntary, stimulated by the desire of the subject to redirect his/her attention to a new object of regard, or can be involuntary. Examples of involuntary versions include reflex movements of the eyes stimulated by reaction to auditory or visual stimuli and reflex movements such as those stimulated by the vestibular system.

2.4 Vergence Movements Vergence movements of the eyes are simultaneous movements of the eyes in opposite directions. Vergence movements are utilized to maintain fixation of the object of regard on the fovea of each eye as the object changes distance from the eyes, such as visually tracking an object that is moving toward the eyes from a distant point. In the latter example, the two eyes must

Fig. 2.2. Yoke muscles primarily responsible for movement of the eye into the six diagnostic positions of gaze. (LIO Left inferior oblique, LIR left inferior rectus, LLR left lateral rectus, LMR left medial rectus, LSO left superior oblique, LSR left superior rectus, RIO right inferior oblique, RIR right inferior rectus, RLR right lateral rectus, RMR right medial rectus, RSR right superior rectus)

 

2.6 Sherrington’s Law of Reciprocal Innervation The concept of reciprocal innervation of pairs of extraocular muscles was first conceived by Descartes in the 1600s. The physiologic basis for reciprocal innervation was demonstrated by Sherrington in 1894 [1]. Sherrington’s law of reciprocal innervation simply states that when an impulse to contract is received by the agonist muscle in an eye, the antagonist muscle receives an inhibitory impulse. It is not clear if the inhibitory impulse is merely absence of innervation or active inhibition. Thus, normal movement of the globe always involves contraction of one or more extraocular muscles and relaxation of the respective antagonist(s).

2.7 Herring’s Law of Equal Innervation Under normal circumstances, innervation to the extraocular muscles in the two eyes must occur in parallel. In other words, neural stimulation to perform eye movements is always integrated. Thus yoked muscles in the two eyes always receive equal innervation under normal circumstances. This basic law of ocular motility is known as Herrings’s law of equal innervation. The law applies to both voluntary and involuntary eye movements, which are always coordinated and the law applies to both versions (simultaneous eye movements in the same direction) and vergences (simultaneous eye movements in opposite directions). Herring’s law of equal innervation is hardwired in that a single fiber tract from the cortical centers is

Fig. 2.3. Cardinal positions of gaze. The central position is known as the primary position. The secondary positions are up, down, right, and left and occur around the x-axis and z-axis. The tertiary positions are

2.1  Axes of Ocular Rotation and Listing’s Plane

directed to the cranial nerve nuclei involved in eye movements and impulses are distributed to appropriate muscle pairs in each eye by further hardwiring between these various cranial nerve nuclei. Herring’s law is the explanation for the fact that patients with paralytic or restrictive strabismus have a primary and a secondary deviation (Chap. 4).

2.8 Donders’ Law Because the eye has 3 degrees of freedom for rotary movements around the major axes of rotation, in theory there are an infinite number of possible coordinates for designating the position of the globe in any eccentric position of gaze. Fortunately, movements around the y-axis (anteroposterior axis) are very restricted. Restriction of movement around the y-axis is important for spatial orientation and greatly simplifies both the study of ocular motility and the treatment of strabismus. Donders [2] determined that there was a constant and defined amount of torsion (x-axis and z-axis coordinates relative to the y-axis) present for each gaze position away from the primary position and this principle is known as Donders’ law.

2.9 Cardinal and Diagnostic Positions of Gaze There are nine cardinal positions of the gaze for distance fixation (>Fig. 2.3). The primary position can be considered the position when the eyes are looking straight ahead and the body and the head are erect. Pure rotations around the z-axis and

up right, up left, down right, and down left and occur around oblique axes of rotation in Listing’s plane

23

24

Physiology of Eye Movements

Chapter 2

x-axis move the eye into positions designated as the secondary positions of gaze: adduction, abduction, elevation, and depression. The oblique positions represent tertiary positions of gaze and occur around oblique axes of rotation in Listing’s plane. These nine cardinal positions of gaze are used to analyze incomitant strabismus and play in important role in diagnosis and in surgical planning. There are six diagnostic positions of gaze (>Fig. 2.2). The diagnostic positions of gaze are useful clinically to evaluate the action of individual extraocular muscles in each eye. In each of the diagnostic positions of gaze, function of a single extraocular muscle in each eye is emphasized. Thus, abnormalities of eye movements into a given diagnostic position of gaze are usually attributed, in large part, to abnormalities in the function of a single extraocular muscle.

2.10 Actions of Individual Muscles For purposes of discussion, the individual actions of each extraocular muscle are reviewed in isolation. In reality, extraocular muscles never act in isolation. For example, contraction of the medial rectus muscle is primarily responsible for adduction, but both the superior rectus muscle and the inferior rectus muscle also make a small contribution to adduction [3]. Additionally, traditional descriptions of the individual actions of extraocular muscles are based on simple models of orbital anatomy and function, not taking into account the effect of the muscle pulleys on altering both the paths of the rectus muscles in the orbit and in altering muscle function (Chap. 1). Simply put, the actions of the extraocular muscles and their impact on changes in the position of the globe are much more complex than traditionally taught and reviewed here [4]. Nevertheless, for clinical purposes, this simplified description of the functions of the extraocular muscles is satisfactory for both understanding and managing the vast majority of patients with strabismus.

2.10.1 Horizontal Rectus Muscles The actions of the horizontal rectus muscles are relatively simple if their function is evaluated only from the standpoint of eye movement with contraction of these muscles from the primary position. The muscle plane of the horizontal rectus muscles corresponds with horizontal plane of the eye, incorporating the x-axis and y-axis. When the eye is in the primary position, the horizontal rectus muscles produce isolated rotation around the z-axis. Thus the lateral rectus muscle is a pure abductor and the medial rectus muscle is a pure adductor (>Fig. 2.4). However, the actions of the horizontal rectus muscles become more complex when the eyes are not rotating purely along the horizontal plane. For example, if the eye is both abducting and depressing simultaneously, the medial rectus muscle also produces some degree of depression. Alterations

Fig. 2.4. The muscle plane of the medial rectus muscle is perpendicular to its axis of rotation, resulting in pure adduction from the primary position

in the function of the horizontal rectus muscles with movement of the globe out of the horizontal plane of rotation may help to explain certain aspects of ocular movement disorders that occur in patients with strabismus, such as over elevation with adduction, which might occur with contraction of a medial rectus that has been displaced upward.

2.10.2 Vertical Rectus Muscles The actions of the vertical rectus muscles are more complex than those of the horizontal rectus muscles. The actions are more complex because the vertical rectus muscle planes do not coincide with either of the major axes of rotation of the globe. The axis of rotation of the superior rectus muscle is obliquely oriented between the x-axis and the y-axis of rotation (>Fig. 2.5). Though it is not technically accurate, for clinical purposes, the muscle planes of the superior and inferior rectus muscles can be considered to coincide so that there actions fully compliment each other [5]. When the eye is in the primary position, the muscle plane of the superior and inferior rectus muscles forms an angle of approximately 23° with the y-axis (>Fig. 2.5). The insertions of the rectus muscles are located more lateral than their origins, so that the planes of the vertical rectus muscles diverge from each other in the two eyes. Careful study of Fig. 2.5 allows deduction of the primary and other actions of the vertical rectus muscle in moving an eye from the primary position.

 

The major action of the superior rectus muscle from the primary position is to produce elevation of the globe. Because of the relationship between the muscle plane of the superior rectus muscle and the cardinal axes of rotation of the globe, contraction of the superior rectus muscle also produces adduction and a small amount of incycloduction (>Table 2.1). If the globe is abducted approximately 23°, the muscle plane of the superior rectus muscle roughly coincides with the y-axis of the globe. At this point, the superior rectus muscle technically becomes a pure elevator, hence the vertical action of the superior rectus muscle is maximal when the globe is abducted. Alternatively, when the eye is abducted, incycloduction , the tertiary action of the superior rectus muscle, predominates. The superior rectus muscle can never produce pure incycloduction, however, because the eye cannot be adducted 67° from the primary position, the point at which the superior rectus muscle would theoretically produce almost pure incycloduction. Thus, while incycloduction is maximal when the eyes adducted, a significant degree of elevation function persists. The function of the inferior rectus muscle is comparable to that just described for the superior rectus muscle, with obvious modifications. From the primary position, the inferior rectus muscle functions primarily as a depressor. It also produces excycloduction and a small amount of adduction (>Table 2.1). The depressor function of the inferior rectus muscle is maximal when the globe is in abduction and, for practical purposes, the inferior rectus muscle acts as a pure depressor when the globe is abducted approximately 23° from the primary position, where the muscle plane is parallel with the y-axis. Like the superior rectus muscle, the cycloduction function of the inferior rectus muscle is maximal when the globe is adducted (>Fig. 2.5).

2.10  Actions of Individual Muscles

25

2.10.3 The Oblique Muscles For practical purposes, we will consider that the muscle planes of the superior oblique tendon and inferior oblique muscle coin­cide, a reasonable assumption based on available evidence [5]. Because the path of the superior oblique muscle/tendon is diverted acutely at the trochlea, the trochlea is the functional origin of the superior oblique muscle. The muscle plane and functions of the superior oblique muscle are thus all related to the superior oblique tendon. Like the vertical rectus muscles, the muscle planes of the oblique muscles do not coincide with any of the three major axes of rotation of the globe. Thus, like the vertical rectus muscles, the actions of the oblique muscles are complex [6]. When the eye is in the primary position, the axis of rotation of the superior oblique tendon is oriented obliquely between the y-axis and the x-axis. The muscle plane of the superior oblique tendon forms an angle of approximately 54° with the y-axis or median plane of the eye (>Fig. 2.6). The major action produced on a globe that is in the primary position during isolated contraction of the superior oblique muscle is incycloduction. Because of the relationship between the muscle plane of the superior oblique tendon and the major axes of rotation of the globe, contraction of the superior oblique muscle also produces depression and a small amount of abduction (>Table 2.1). If the globe is adducted, the angle between the median plane (y-axis) of the eye and the muscle plane is reduced, enhancing the depressor function of the superior oblique muscle. If the eye could be adducted 54°, the superior oblique muscle would act as a pure depressor. With abduction of the eye, the angle between the muscle plane and the median plane of the globe increases, enhancing the cycloduction function of the superior oblique muscle. When the eye is abducted approximately 36°, the superior oblique muscle action is primarily one of pure incycloduction (>Fig. 2.6). The functions of the inferior oblique muscle are comparable to those just described for the superior oblique muscle, with obvious modifications. From the primary position, the inferior oblique muscle functions primarily to produce excyTable 2.1. Actions of the extraocular muscles on the globe from the primary position

Fig. 2.5. Relationship of the muscle plane of the vertical rectus muscles to the horizontal (x-axis) and vertical (z-axis) axes of rotation

Muscle

Primary

Secondary

Tertiary

Medial rectus

Adduction

–

–

Lateral rectus

Abduction

–

–

Superior rectus Elevation

Incycloduction Adduction

Inferior rectus

Depression

Excycloduction Adduction

Superior oblique

Incycloduction Depression

Abduction

Inferior oblique

Excycloduction Elevation

Abduction

26

Physiology of Eye Movements

Chapter 2

Fig. 2.6a b. a Relationship of the muscle plane of the oblique muscles to the y-axis of rotation. b The superior oblique muscle functions to produce almost pure incycloduction when the eye is abducted approximately 36°

cloduction. It also produces elevation and a small amount of abduction (>Table 2.1). The elevator functions of the inferior oblique muscle are enhanced in adduction while its function of excycloduction is enhanced in abduction. The inferior oblique muscle would function essentially as a pure elevator if the eye could be adducted approximately 51° and its function of excycloduction greatly predominates when the eye is abducted approximately 39°.

References 1. 2. 3.

4.

5. 6.

Sherrington CS (1894) Experimental note on two movements of the eyes. J Physiol (Lond) 17 Donders FC (1848) Beitrag zur lehre von den Bewegungen des menschlichen Auges. Holland Beitr Anat Physiol Wiss 1:384 Chamberlain WP Jr. (1954) Ocular motility in the horizontal plane: an experimental study of the primary and secondary horizontal rotators in the rhesus monkey. Trans Am Ophthalmol Soc 52:751–810 Krewson WE (1950) The action of the extraocular muscles: a method of vector-analysis with computations. Trans Am Ophthalmol Soc 48:443–486 Jampel RS (1970) The fundamental principle of the action of the oblique ocular muscles. Am J Ophthalmol 69:623–638 Jampel RS (1966) The action of the superior oblique muscle. An experimental study in the monkey. Arch Ophthalmol 75:535–544

Chapter

Indications for Strabismus Surgery

3

3 Traditionally, the goal of strabismus treatment has been to realign the visual axes in order to eliminate diplopia, or to produce, maintain, or restore binocular vision. Additionally, surgery to improve an abnormal head posture, eliminate abnormal eye movements, or simply to restore the normal anatomical position of the eyes are well-accepted indications for surgery [1]. Facilitation of the development of binocular vision is classically demonstrated in the treatment of idiopathic infantile esotropia (congenital esotropia). Historically, Worth’s sensory concept of congenital esotropia proposed a disorder that resulted from a deficit in the “fusion center” within the central nervous system [2]. According to this theory, the goal of producing binocular vision was hopeless. He theorized that it was not possible to restore this congenitally absent neural function. Data supporting Worth’s theory were obtained at a time when strabismus surgery was rarely performed prior to the age of 2 years. Until the 1960s the results of surgical treatment of patients with congenital esotropia almost universally supported this pessimistic view.

3.1 Restoration of Binocular Vision Chavasse challenged Worth’s theory. He suggested that normal binocular vision could be achieved through facilitation of conditioned reflexes that depend on early ocular alignment for proper development [3]. He considered congenital esotropia to be a strictly mechanical problem. He believed that most cases of congenital esotropia were potentially curable if ocular misalignment could be eliminated early in infancy. Because Chavasse lived before surgery was commonly performed to treat strabismus, support for this theory was limited until Ing and co-workers [4] began to report favorable binocular vision in some infants who underwent strabismus surgery between the ages of 6 months and 2 years. These encouraging results became the basis for the justification of early surgery in children with congenital esotropia. It is now widely accepted that early surgical intervention can result in restoration of some level of binocular function in a large number of operated children. However, the level of binocular function obtained in patients with idiopathic infantile esotropia is almost uniformly subnormal. Subnormal binocular vision as described by von Noorden [5] or the mono-

fixation syndrome, as described by Parks [6], is considered the optimal result in children with idiopathic infantile esotropia by most pediatric ophthalmologists (>Table 3.1). Monofixation syndrome is associated with peripheral fusion, low-grade stereopsis, and vergence amplitudes capable of maintaining alignment within approximately 10 prism diopters, despite deficient stereopsis and a central suppression scotoma in one eye during binocular viewing. Patients who develop this level of binocular vision are more likely to maintain normal ocular alignment throughout their life [7]. Therefore, early surgery in an effort to achieve monofixation syndrome or subnormal binocular vision is desirable. Most strabismus surgeons recommend strabismus surgery to correct idiopathic infantile esotropia early in infancy, preferably after amblyopia, if present, has been adequately treated. Older children with normal binocular vision, but who remain immature from the standpoint of cortical visual development, are still at risk for the development of abnormal adaptations in their binocular system if strabismus develops. Suppression and abnormal retinal correspondence are frequently seen in disorders such as intermittent exotropia. These adaptations may allow an intermittent deviation to become manifest more frequently or even to become constant. Once these adaptations develop, they may place a child at higher risk for the recurrence of strabismus later in life, even after successful surgical realignment. In patients with intermittent exotropia, for example, strabismus surgery is often recommended when the deviation increases in frequency and there is evidence that suppression has become more ingrained. The development of suppression may be inferred when the child no longer closes one eye when the deviation is present or when the deviation is manifest for a substantial amount of time or is constant. Surgery before these abnormal adaptations are well developed may be helpful in providing long-term stable ocular alignment. A young child with a deviation that is frequently manifest, but who has not yet developed suppression, may particularly benefit from early surgical intervention. Table 3.1. Elements of the monofixation syndrome Absence of bifoveal fixation Peripheral fusion Central facultative suppression scotoma

28

Indications for Strabismus Surgery

3.2 Diplopia In older children, and adults, who are visually mature, sensory adaptations to a new-onset ocular deviation typically do not occur. If the patient has a history of normal ocular alignment and develops a deviation in later life, the patient will experience diplopia when the eyes are not aligned. Patients with this history who do not report diplopia are generally ignoring the extra image and are not aware of its presence. The degree of visual disturbance experienced is dependent upon several factors. The frequency of the deviation is often the most important factor in determining the patient’s tolerance of symptoms. However, other factors may be of equal importance. Interestingly, deviations that are large are often less bothersome to the diplopic patient than smaller deviations. The explanation for this is the fact that it is often easier for the patient to detect the “real” object of regard when the second image is separated in space by a large distance, and it is simultaneously easier for the patient to ignore a distant second image. When the two images are close together or overlapping, as occurs with small angle strabismus, the abnormal visual experience is usually much more bothersome. The position(s) of gaze where the double vision occurs is also an important consideration when evaluating diplopic patients and when discussing the potential benefit of treatment. Deviations that occur in primary position, down gaze, or in the reading position tend to be the most troublesome. Many patients can compensate for deviations that produce diplopia in side gaze and up gaze by turning their head, rather than moving their eyes, when viewing targets in these gaze positions. Such adaptations are less useful for near vision and for down gaze, because of both the frequency with which the eyes are used in these positions, and the need for optical correction (bifocal) for near vision in older patients. Diplopia that occurs only in up gaze tends to be the least bothersome and often well tolerated without treatment. This may not be the case if the diplopia develops within a few degrees of elevation of the eyes from the primary position. There are many exceptions to these general rules of thumb. Patients in some occupations, such as carpentry work that requires frequent use of up gaze, may be less tolerant of diplopia in up gaze, for example. Patients who are experiencing debilitating diplopia can almost always benefit from treatment. If the deviation is small and relatively comitant, prism added to spectacle lenses may offer significant relief from symptoms. If the deviation is larger, prism will often produce unwanted image distortion and the lenses themselves are often too heavy and uncomfortable for reasonable wear. Though there are exceptions, patients rarely tolerate prism correction of a deviation greater than 8–10 prism diopters, in our experience. Surgery will eliminate bothersome diplopia in most patients, though the addition of a small amount of prism in the patient’s spectacle lenses is required for some patients with a small residual deviation producing symptomatic diplopia after surgery. Patients who otherwise do not require spectacle correction or who prefer wearing contact lenses often request surgery even for small deviations to avoid the need for prism. This

Chapter 3

may seem an unreasonable request on the surface. However, the need for prism glasses to achieve fusion and single vision is not comparable to the need for glasses to correct a refractive error. Even patients with significant uncorrected refractive errors are usually able to function relatively well in many activities of daily living without significant difficulty. In contrast, patients with diplopia are rarely able to comfortably participate in most activities without the need to constantly close one eye to eliminate diplopia. Thus, patients who find the use of prism glasses undesirable may be excellent surgical candidates.

3.3 Incomitant Strabismus A significantly incomitant deviation with symptomatic diplopia is only occasionally successfully treated with prism and thus surgery is usually the primary treatment option. A surgical plan that takes into account the etiology of the incomitant strabismus can usually provide a significantly expanded field of single vision compared with prism in such patients. Superior oblique paresis is a typical example. Prism correction may provide single vision in primary position but most patients continue to experience bothersome diplopia in other important fields of gaze despite the use of prisms. A well considered surgical procedure can usually collapse the incomitant deviation produced by a superior oblique paresis, resulting in a larger field of single binocular vision.

3.4 Asthenopia Even if the patient’s deviation remains latent most of the time, it may give rise to bothersome symptoms of asthenopia, in the absence of diplopia. Such deviations may be overlooked on cursory and sometimes even detailed initial examination. Symptoms may include eyestrain, reading difficulties, headaches, vague symptoms of fatigue or other symptoms with prolonged eye use. Asthenopia is usually not present with small horizontal phorias but may be experienced with medium to large horizontal phorias especially those that approach the relatively large horizontal vergence amplitudes. However, we occasionally examine patients with small angle exophorias who experience significant symptoms during reading. Small vertical phorias, on the other hand, often produce asthenopia due to the smaller vertical fusional vergence amplitudes possessed by most normal people (>Table 3.2). Surgery to eliminate a Table 3.2. Average vergence amplitudes (measurements in prism diopters using a prism bar) [27] Testing Distance

Convergence

Divergence

Sursumvergence

At 6 m

14.1

  5.82

2.54

At 25 cm

38.02

16.47

2.57

 

symptomatic latent deviation can provide great comfort to the patient. If there is a question as to whether or not a strabismic deviation is responsible for a patient’s visual complaints, a trial of prism correction or monocular occlusion is often of great diagnostic value. Resolution or marked reduction of symptoms with either of these diagnostic trials is good evidence that the latent strabismus is contributing to the problem.

3.5 Asymptomatic Patients

3.6  Compensatory Head Posture

if even rudimentary fusion is restored. Other ophthalmologists believe that surgery should be performed if the deviation is significant as determined by the patient and/or family. These ophthalmologists feel that there is no functional deficit that can be demonstrated in real world situations in patients who do not have peripheral fusion.

3.6 Compensatory Head Posture

Treatment of strabismus in patients who are not experiencing diplopia or other symptoms, but who have an angle of deviation too large for the development of binocular vision, may still be justified, though not all ophthalmologists agree. Some ophthalmologists believe that any deviation greater than 8 prism diopters warrants surgical correction in order to reduce the deviation and provide a chance for the patient to develop some degree of fusion. This goal can be achieved often, even in older patients with long-standing uncorrected deviations [8]. Morris and co-workers [8] operated on 24 adult patients with longstanding strabismus, 7 of whom had congenital esotropia or exotropia. All patients developed some degree of fusion after surgery and 50% achieved stereopsis. Eight of these were in the congenital group. These ophthalmologists believe that even peripheral fusion is beneficial to patients and that the prognosis for maintaining ocular alignment long term will be enhanced

Some patients are able to achieve single vision only in eccentric gaze. Such patients have an incomitant deviation and will typically develop a compensatory head posture to take advantage of the fusion that they can achieve in the eccentric gaze position (>Fig. 3.1). Paralytic, restrictive and A-pattern and V-pattern strabismus are frequent causes of incomitant deviations that are often associated with a compensatory head posture. Thyroid-related orbitopathy, for example, often leads to the development of a restrictive strabismus that necessitates the patient to maintain an awkward and uncomfortable head position to avoid diplopia. Traditionally, it has been taught that strabismus surgery on patients with thyroid-related ophthalmopathy should be delayed until the ocular deviation has been stable and unchanging for at least 3–6  months. This is our general treatment philosophy, though we have treated several patients who were so severely disabled by their abnormal head posture that we felt earlier surgical intervention prior to stabilization of

Fig. 3.1a,b. a A patient who presented with a long-standing face turn and complaints of diplopia in other gaze positions. b The same patient as seen in a childhood photograph demonstrating the same head tilt.

(Reprinted with permission from Nelson and Olitsky, Harley’s pediatric ophthalmology, 5th edn. Lippincott, Williams & Wilkins, 2005, Fig. 9.26, page 170 [28])

29

30

Indications for Strabismus Surgery

Chapter 3

Fig. 3.2a,b. Large upshoots in Duane syndrome are a reasonable indication for surgery

the strabismus measurements was justified [9]. The need for reoperation is probably greater when surgery is performed prior to documented stabilization of the deviation, but patients we have treated early have been able to return to work and other activities and have felt that the tradeoff was reasonable.

3.7 Miscellaneous Surgical Indications In patients with a congenital or early-onset superior oblique palsy, earlier surgical intervention may prevent development of the facial asymmetry that has been reported with this disorder [10, 11] (Chap. 1). Patients with Duane syndrome who have pronounced upshoots, downshoots, or globe retraction due to co-contraction may benefit from strabismus surgery to blunt these conditions, with a reasonable risk to benefit profile (>Fig. 3.2a, b).

3.8 Nystagmus Extraocular muscle surgery may also be of value in some patients with nystagmus, including patients with and without a compensatory head posture. Kestenbaum [12], Anderson [13], and Goto [14] each independently reported different surgical procedures to move the null zone closer to the primary position in patients with nystagmus and a compensatory head posture (>Fig. 3.3). Each of these procedures accomplished the same goal of moving the eyes in the direction of the compensatory head posture, thus moving the null zone closer to the primary position. While the procedure described by Goto, which involved isolated resection of a rectus muscle, has largely been abandoned as a primary treatment of nystagmus, both the Kestenbaum and Anderson procedures are frequently utilized, though both have been modified significantly from their original descriptions. The Anderson technique involves recession of a rectus muscle in each eye, while the Kestenbaum procedure involves recession of a rectus muscle in each eye as well as resection of a rectus muscle in each eye. For an Anderson procedure to be effective, the rectus muscles must be recessed well posterior to the equator of the globe in each eye. Our typical approach is to perform an Andersontype procedure. If a residual face turn persists, the treatment is augmented by performing resection surgery of the unoperated

Table 3.3. Surgical dose for Kestenbaum surgery to treat a compensatory head posture due to nystagmus (example for a left face turn) [16]. (LLR Left lateral rectus, LMR left medial rectus, RLR right lateral rectus, RMR right medial rectus) Resect LLR

Recess LMR

Resect RMR

Recess RLR

15° face turn

  8.0 mm

5.0 mm

6.0 mm

  7.0 mm

30° face turn

11.0 mm

7.0 mm

8.5 mm

10.0 mm

45° face turn

13.0 mm

8.0 mm

9.5 mm

11.0 mm

antagonist muscle in each eye (Fig. 3.3c). The original technique described by Kestenbaum was later modified to prevent the development of postoperative strabismus [15], to treat larger face turns [16], as well as to improve a vertical compensatory head posture due to the presence of a null zone in vertical gaze [17] (>Table 3.3). More recently, four-muscle retro-equatorial recessions of the horizontal muscles has been advocated by several surgeons in an effort reduce the intensity of nystagmus (>Fig. 3.3d). Reports on this procedure have described minor objective, but often significant subjective improvement of visual function [18, 19], and this has been our experience with this procedure also. Recently, four-muscle tenotomy (two rectus muscles in each eye), which involves detachment and immediate reattachment to the original insertion, has been reported to reduce the intensity of nystagmus, resulting in improved visual function by altering foveation time [20, 21].

3.9 Expansion of the Field of Vision in Patients with Esotropia Although reestablishing binocular vision, eliminating diplopia, expanding the area of single binocular vision, and improving vision and/or a compensatory head posture in patients with nystagmus have been the most important historical roles for strabismus surgery, recent studies have demonstrated additional benefits that are unrelated to these traditional goals. Kushner described a series of patients who underwent surgery for the treatment of esotropia [22]. Each patient achieved a significant expansion of their binocular visual field consistent with the degree to which their eyes were surgically straight-

 

3.10  Psychosocial and Vocational Indications

Fig. 3.3a–d. Possible surgical approaches to treating nystagmus with a right face turn and a null zone in left gaze. a Bilateral recess/resect operation, b bilateral recessions, c bilateral resections, and d four-rectus-muscle recession procedure

ened. This study demonstrated a benefit to strabismus surgery unrelated to the patient’s level of binocular vision [23].

3.10 Psychosocial and Vocational Indications In addition to the improvements obtained in binocular function and the binocular visual field, strabismus surgeons and patients frequently relate anecdotal stories about the psychosocial and vocational benefits obtained after ocular alignment has been improved following strabismus surgery. After successful strabismus surgery, many patients relate improvement in self-

image, interpersonal relationships, and school and work performance. In addition, operated patients often feel that others view them more positively after their strabismus is rendered less obvious with surgery. Until recently, these anecdotal experiences have been the only evidence available to support the role of strabismus surgery in patients who are not anticipated to achieve a significant functional physiologic improvement in their visual system through surgery. Several studies have now been published in the medical literature providing scientific evidence that these improvements in psychosocial and vocational experiences are, in fact, common following strabismus surgery. Studies have demonstrated that strabismus creates a significant negative psychosocial impact on patients [24]. Stra-

31

32

Indications for Strabismus Surgery

bismus can create biases which have a detrimental impact on socialization and employability [25]. These socialization difficulties begin early in childhood and continue into adult life. Strabismus can adversely impact interpersonal relationships between children and between adults, and can adversely impact the relationships between teachers and affected school children which could have a detrimental effect on educational performance [26]. These biases have been shown to begin early in childhood and continue through the adult years. The negative consequences of these biases affect not only individual patients, but also society as a whole. Prior to the formal publication of data on the impact of strabismus on these important aspects of life, the treatment of strabismus in adults who did not experience diplopia or who did not have binocular potential was often regarded as purely “cosmetic.” Use of the term cosmetic in the treatment of affected patients is inaccurate. Cosmetic surgery is performed to enhance or beautify. Strabismus is the result of an underlying disease process, abnormal binocular vision, which leads to an objective deviation from a normal appearance. Because of the pathophysiology involved in the development of strabismus, and the potentially negative psychosocial effects of this disorder, surgery should be referred to as “reconstructive.” We often utilize the terms socially significant strabismus and vocationally significant strabismus in this setting. Surgery is indicated to provide the only ocular alignment status that is normal for a human, straight. The indications for strabismus surgery reviewed in this chapter (>Table 3.4) should be considered general in nature and are neither absolute nor all-inclusive. The risks, benefits, and alternatives to surgery should be individually considered with each patient. Some patients will benefit greatly from surgery even when the indications for surgery may initially appear to be small. Likewise, other patients may achieve little personal benefit even when the indications for surgical intervention appear obvious to the surgeon. In short, strabismus surgery should not be undertaken just because ocular misalignment is present, and should not be denied just because a deviation is small or the patient is not anticipated to achieve gains in binocular function.

References 1. 2. 3.

4. 5.

6.

Paysse EA (2001) Adult strabismus: goals of realignment surgery. Binocul Vis Strabismus Q 16:9–10 Worth C (1903) Squint, its causes and treatment. Bailliere, Tindall, and Cox, London Chavasse F (1939) Worth’s squint on the binocular reflexes and the treatment of strabismus, 7th edn. Blakiston’s, Philadelphia, Pa. Ing M, Costenbader FD, Parks MM, Albert DG (1966) Early surgery for congenital esotropia. Am J Ophthalmol 61:1419–1427 von Noorden GK (1988) A reassessment of infantile esotropia. XLIV Edward Jackson memorial lecture. Am J Ophthalmol 105:1–10 Parks MM (1969) The monofixation syndrome. Trans Am Ophthalmol Soc 67:609–657

Chapter 3 Table 3.4. Possible indications for strabismus surgery Develop, restore or maintain binocular vision Resolution or improvement of diplopia Resolution or improvement of asthenopia Resolution or improvement of a compensatory head posture Improvement of anomalous eye movements Improvement of vision in a patient with nystagmus Expansion of visual field in a patient with esotropia Improvement in psychosocial function Improvement in vocational prospects

7.

8.

9.

10. 11.

12. 13. 14. 15. 16.

17.

18.

19.

20.

Arthur BW, Smith JT, Scott WE (1989) Long-term stability of alignment in the monofixation syndrome. J Pediatr Ophthalmol Strabismus 26:224–231 Morris RJ, Scott WE, Dickey CF (1993) Fusion after surgical alignment of longstanding strabismus in adults. Ophthalmology 100:135–138 Coats DK, Paysse EA, Plager DA, Wallace DK (1999) Early strabismus surgery for thyroid ophthalmopathy. Ophthalmology 106:324–329 Wilson ME, Hoxie J (1993) Facial asymmetry in superior oblique muscle palsy. J Pediatr Ophthalmol Strabismus 30:315–318 Goodman CR, Chabner E, Guyton DL (1995) Should early strabismus surgery be performed for ocular torticollis to prevent facial asymmetry? J Pediatr Ophthalmol Strabismus 32:162–166 Kestenbaum A (1953) [New operation for nystagmus.] Bull Soc Ophtalmol Fr 6:599–602 Anderson JR (1953) Causes and treatment of congenital eccentric nystagmus. Br J Ophthalmol 37:267–281 Goto N (1954) A study of optic nystagmus by the electro-oculogram. Acta Soc Ophthalmol Jpn 58:851–854 Parks MM (1973) Symposium: nystagmus. Congenital nystagmus surgery. Am Orthopt J 23:35–39 Calhoun JH, Harley RD (1973) Surgery for abnormal head position in congenital nystagmus. Trans Am Ophthalmol Soc 71:70– 83; discussion 84–87 Yang MB, Pou-Vendrell CR, Archer SM, Martonyi EJ, Del Monte MA (2004) Vertical rectus muscle surgery for nystagmus patients with vertical abnormal head posture. J AAPOS 8:299–309 Helveston EM, Ellis FD, Plager DA (1991) Large recession of the horizontal recti for treatment of nystagmus. Ophthalmology 98:1302–1305 von Noorden GK, Sprunger DT (1991) Large rectus muscle recessions for the treatment of congenital nystagmus. Arch Ophthalmol 109:221–224 Hertle RW, Dell’Osso LF, FitzGibbon EJ, Yang D, Mellow SD (2004) Horizontal rectus muscle tenotomy in children with infantile nystagmus syndrome: a pilot study. J AAPOS 8:539–548

  21. Hertle RW, Anninger W, Yang D, Shatnawi R, Hill VM (2004) Effects of extraocular muscle surgery on 15 patients with oculocutaneous albinism (OCA) and infantile nystagmus syndrome (INS). Am J Ophthalmol 138:978–987 22. Kushner BJ (1994) Binocular field expansion in adults after surgery for esotropia. Arch Ophthalmol 112:639–643 23. Wortham ET, Greenwald MJ (1989) Expanded binocular peripheral visual fields following surgery for esotropia. J Pediatr Ophthalmol Strabismus 26:109–112 24. Olitsky SE, Sudesh S, Graziano A, Hamblen J, Brooks SE, Shaha SH (1999) The negative psychosocial impact of strabismus in adults. J AAPOS 3:209–211

References 25. Coats DK, Paysse EA, Towler AJ, Dipboye RL (2000) Impact of large angle horizontal strabismus on ability to obtain employment. Ophthalmology 107:402–405 26. Uretmen O, Egrilmez S, Kose S, Pamukcu K, Akkin C, Palamar M (2003) Negative social bias against children with strabismus. Acta Ophthalmol Scand 81:138–142 27. Berens CEA (1927) Routine examination of the ocular muscles and non-operative treatment. Am J Ophthalmol 10:910 28 Nelson LB, Olitsky SE (2005) Harley’s pediatric ophthalmology, 5th edn. Lippincott, Williams and Wilkins, Baltimore

33

Surgical Decision Making

Chapter

4

4 Proper surgical technique is obviously a prerequisite when caring for the strabismus patient. Decisions regarding the type and amount of surgery to be performed as well as the planned surgical approach are equally important. This chapter will provide an overview of the decision-making process that is vital to maximizing the outcomes of strabismus surgery. It should be noted that these are general suggestions and ideas based upon our experience. There are many ways to properly treat most strabismus disorders. For most strabismus problems, there is no single approach that is absolutely correct, or necessarily clearly better than every other choice. However, there are often clear advantages of some choices over others when considering the range of possible treatment options for any given condition. Each surgeon ultimately develops a pattern of treatment based upon his or her training, experiences and consultations or discussions with other strabismus surgeons.

4.1 Preoperative Evaluation 4.1.1 Strabismus History In order to make good decisions when planning a strabismus procedure, it is important to have the necessary data available that will make these decisions possible. In the examination room, this starts with a thorough history. Knowing a patient’s prior history of treatment for strabismus and/or amblyopia is important, but full details of treatments received as a child are often not available. A history of prior strabismus surgery may lead the surgeon to choose muscles on which to operate that would not otherwise be the first choice if no prior surgery had been performed. Old records and/or operative notes can be helpful in these cases. However, old records and clinical notes are often not available due to the age of the patient, their relocation, or an inability to obtain the records for other reasons. In these cases, the history obtained from the patient may help to determine the type of surgery previously performed. A patient who had surgery before 1 year of age most likely underwent surgery for congenital esotropia. Based upon that knowledge, it can often be extrapolated that both medial rectus muscles were operated or a recess/resect procedure was performed in one eye. This can be further supported by examination of the

conjunctiva for evidence of previous conjunctival incisions. Such information is helpful when developing a surgical plan for an older patient who may later present with esotropia; for example, where the surgical plan may call for resection of both lateral rectus muscles if previous medial rectus recessions have been performed, or a recess and resect operation in one eye if it can be determined that surgery was previously only performed on one eye.

4.1.2 Ocular Motor and Sensory Examination Following the history, a thorough examination of the ocular motor system appropriate for the condition being treated is essential to providing the data necessary to complete the surgical plan. The motility evaluation may include measurements of alignment in primary position, at distance fixation and near fixation, in the diagnostic and cardinal positions of gaze, and in head tilt positions. Evaluation of ductions is also important in patients with limitations of globe excursion noted during testing of versions. Measurements of motor fusional amplitudes may be helpful in select patients. For example, knowing the convergence and divergence fusional amplitudes of a diplopic patient with an esotropia may allow the surgeon to council the patient on the risk of continued double vision should an overor under-correction occur following surgery. Sensory evaluation may help the surgeon in many different ways. For example, it may help the surgeon to decide on optimal surgical timing in young children with intermittent exotropia, the ability to perform superior oblique tenotomy procedures in patients with A-pattern exotropia or to monitor the success of previous treatments. In the preceding examples, a decline in stereo vision may prompt surgical intervention for intermittent exotropia and a superior oblique tenotomy would probably be avoided in a patient with A-pattern exotropia who had high-grade stereopsis. Another approach to managing the A-pattern would likely be chosen instead to avoid the high risk that the patient will develop symptomatic diplopia and/or lose stereopsis following surgery on the superior oblique tendons in this setting. Some ophthalmologists will repeat motility examinations following monocular occlusion in some patients, such as pat­ ients with intermittent exotropia [1, 2]. Monocular occlusion

36

Surgical Decision Making

for a period of 30 min or longer may uncover a larger deviation and could alter surgical planning. One approach is to attempt to obtain every piece of information on every strabismus patient. Using this approach, the surgeon will always have the ability to decide which data need to be analyzed at a later time. For most patients, this is not only unnecessary but time consuming, inefficient, and taxing for the patient. Rather we suggest a motility evaluation that is tailored to the individual patient and their specific problem. Some surgeons prefer to repeat the motility examination at least once prior to devising a surgical plan and recommending surgery. This has not been our typical practice pattern. For most patients, repeated visits to assess ocular motility appear to be unnecessary. Repeat examinations require the patient and/or parents to take additional time off from work and increase the cost of care by increasing the number of office visits required for treatment. We believe that the surgical decision can and should be made as soon as the ophthalmologist is comfortable with the diagnosis and feels comfortable making treatment recommendations. For many patients, this can occur during the initial examination. For patients in whom the clinical picture is unclear or is changing, follow-up examinations prior to making a surgical recommendation are obviously important.

4.2 Devising the Surgical Plan Once a set of data and information that is sufficient to make a surgical recommendation has been obtained it is time to devise a surgical plan. For some problems, this process will be straightforward and routine and for others significantly more complex. We generally prefer to devise the proposed surgical plan when the patient is still in our presence. This allows for the ability to obtain repeat or additional information if needed and allows us to discuss our recommendations with the patient as they are being formulated. Other surgeons prefer to devise a surgical plan after the patient has left the office. Either approach is reasonable and has both advantages and disadvantages.

4.2.1 Which Eye to Operate? A logical starting point when devising a surgical plan is determining which eye to operate. Factors that may influence this decision include visual acuity, ocular dominance, history of previous strabismus surgery or other surgeries, and the presence of nystagmus or strabismus with a compensatory head posture. Patient fears and patient preference sometimes overrule the surgical plan that the surgeon feels is optimal. For example, patients with a strabismus and diplopia due to a scleral buckle are often, if not usually, reluctant to have surgery performed on their contralateral eye, which they perceive as their “normal” eye, because they fear a complication of surgery. Though the surgeon may feel that surgery on the contralateral eye is the best treatment option, the practical reality is that surgery may need to be performed on the previously buckled eye

Chapter 4

because the patient overrules the initial treatment recommendation. Flexibility during surgical planning is important. It is our general practice to operate on only the eye with the worst vision when there is a significant difference in visual acuity to avoid putting the sound eye at a real, albeit very low risk of a vision-threatening complication. This does not mean that we never operate on the eye with better vision. There are situations in which surgery on the better eye is required to correct the patient’s deviation. Some examples of this are discussed below. In general, because the requirement for obtaining a license to drive is 20/40 in many States, we generally limit surgery to only one eye when the visual acuity is worse than 20/40 in one eye. Some patients with a smaller difference in visual acuity or a strong ocular dominance will strongly consider themselves to have one “good” and one “bad” eye. In these cases, it may be reasonable to operate on both eyes. However, the patient may become anxious when surgery is suggested for their “better” eye. In cases where the outcome would not be altered, we tend to acquiesce to the patient’s wishes. A history of previous strabismus surgery can also be an important factor when determining which eye to operate. If it is determined that the patient had strabismus surgery on only one eye, we will often suggest surgery be performed on the previously unoperated eye as long as the visual acuity is similar in both eyes. This might mean performing a monocular recess/resect procedure that would normally be our second option to a bilateral symmetric recession procedure for the same disorder, if there were not a history of previous history of surgery. The need to treat a compensatory face turn associated with nystagmus or an incomitant strabismus will also lead to the decision to operate one eye over another, as discussed below. In some strabismus disorders, the need to operate on a specific eye is readily apparent to the surgeon but may not be apparent to the patient and/or parent. For example, the need to weaken the superior oblique tendon of patients with Brown syndrome is clear once the diagnosis has been made. However, parents and patients are often under the impression that it is the contralateral eye that moves “too much” and is therefore the eye that requires surgery. It is important to educate patients and parents as part of the decision-making, educational, and informed consent process when this confusion occurs. It is interesting to us that even with careful preoperative discussion of treatment recommendations with patients and after having had patients accurately repeat to us their basic understanding of the surgical recommendations in the office, that patients sometimes show up on the day of surgery unaware that surgery is going to be performed on the eye that they did not believe needed to be operated. We routinely review the proposed surgical plan with patients and/or parents on the day of surgery to mitigate this confusion.

4.2.2 How Many Muscles to Operate? For many cases, the number of muscles on which to operate is the next logical step in the decision-making process. The number of muscles on which to operate is most commonly

 

dictated by the size of the preoperative deviation. Treatment recommendations vary for horizontal deviations depending on the surgeon. Some strabismus surgeons prefer surgery on two muscles for most cases, except those with very small deviations. Others prefer to operate on only a single muscle when the deviation is small to moderate in size. Single-muscle recession and resection has been shown to be a useful surgical technique for moderate angles of strabismus [3, 4]. The purported benefits of single-muscle surgery include shorter anesthesia time, reduced risk because surgery is restricted to only one eye and the sparing of other muscles for future possible surgery. For very large angles of strabismus, some surgeons will operate on a third, or even fourth muscle. This issue has been extensively discussed in the literature with regard to the treatment of congenital esotropia when the deviation angle is large. The use of three- or four-muscle surgery was first advocated when the theoretical limit of recession of the medial rectus was thought to be 5 mm. Now that it is known that much larger recessions of the medial rectus muscles can be safely performed, the need to operate on more than two muscles has been questioned by some surgeons. The hang-back suture technique, which safely facilitates large recessions, can be helpful (Chap. 9). We rarely choose to perform surgery on more than two horizontal muscles to treat a horizontal deviation. This choice spares two of the horizontal rectus muscles for later operation should further surgery be needed. The same issue has been discussed with regard to the treatment of large angle exotropia and we use a similar approach to this problem. A large exotropia may be present in patients with poor vision in one eye. Performing large amounts of surgery on only two muscles in one eye of a patient with a large sensory exotropia may indeed lead to the development of a duction deficit. We warn these patients of this possibility prior to surgery and it has been our experience that these patients are rarely bothered by the small duction deficit that may be produced. Given that this is the tradeoff that eliminates the need to operate on their better seeing eye, patients usually fully support this preoperative recommendation. The need to operate on more than one muscle for the treatment of vertical strabismus follows a similar decision-making process. For a comitant deviation, a single muscle can be recessed or resected for smaller deviations. Vertical deviations larger than approximately 15 prism diopters generally require that a second muscle be operated. In cases of superior oblique palsy with a large deviation angle, multiple options are available. The surgeon may decide to operate on the ipsilateral superior oblique tendon and inferior oblique muscle, the ipsilateral inferior oblique and contralateral inferior rectus muscles or the ipsilateral inferior oblique and superior rectus muscles. When the inferior oblique and superior rectus muscles are operated on simultaneously in the same eye, large recessions of the superior rectus muscle should be avoided. Significant weakening of both elevators of an eye can lead to obvious limitation of elevation postoperatively. The decision regarding which two muscles to operate is primarily based upon the pattern of incomitancy and the surgeon’s preference. A recommendation is made after analysis of the measurements in the

4.2  Devising the Surgical Plan

37

diagnostic positions of gaze and analysis of the patient’s ductions and version. Anterior transposition of the inferior oblique muscles is a useful procedure for the treatment of inferior oblique overaction, dissociated vertical deviation and, in some cases, superior oblique palsy. Anterior transposition leads to an elevation deficiency in many patients, but is usually well tolerated. When the procedure is performed unilaterally, this elevation deficiency may become obvious. It is less noticeable when both eyes are treated. For this reason, we rarely perform unilateral anterior transposition except in unusual circumstances. Severe bilateral inferior oblique overaction may be treated with this procedure; unilateral overaction is generally best treated with an inferior oblique weakening procedure alone. Likewise, bilateral dissociated vertical deviation is often treated with anterior transposition of the inferior oblique muscles, especially if concurrent inferior oblique overaction is present. However, in cases of unilateral dissociated vertical deviation, recession of the superior rectus may be a preferable approach.

4.2.3 Surgical “Dose” The amount of recession or resection performed for a given deviation depends primarily on the size of the deviation. However, many other factors may be considered in a given case including the presence or absence of a duction limitation, level of fusion, associated central nervous system disease, results of forced traction testing, history of previous strabismus surgery, and findings at surgery that could alter the surgical plan such as abnormal anatomy. General guidelines for bilateral surgery to treat esotropia (>Table 4.1) and exotropia (>Table 4.2) are provided. These procedures represent the majority of strabismus operations. These general guidelines require modification depending on other factors as outlined and based on the experience of the individual surgeon. General guidelines

Table 4.1. Suggested surgical guidelines for bilateral recession or resection surgery to treat esotropia. (ET Esotropia, LR lateral rectus, MR medial rectus, OU both eyes) Esotropia (bilateral surgery) ET

MR recession OU

LR resection OU

15

3

4

20

3.5

5

25

4

6

30

4.5

7

35

5

8

40

5.5

9

50

6

60

6.5

70

7

10

38

Surgical Decision Making Table 4.2. Suggested surgical guidelines for bilateral recession or resection surgery to treat exotropia. (LR Lateral rectus, MR medial rectus, OU both eyes, XT exotropia) Exotropia (bilateral surgery)

Chapter 4 Table 4.3. Suggested surgical guidelines for unilateral recession and resection surgery to treat esotropia. (ET Esotropia, LR lateral rectus, MR medial rectus) Esotropia (unilateral surgery)

XT

LR recession OU

MR resection OU

ET

MR recession

15

4

3

15

3

4

20

5

4

20

3.5

5

25

6

5

25

4

6

30

7

6

30

4.5

7

35

7.5

6.5

35

5

8

40

8

7

40

5.5

50

9

50

6

Table 4.4. Suggested surgical guidelines for bilateral recession and resection surgery to treat exotropia. (LR Lateral rectus, MR medial rectus, XT exotropia) Exotropia (unilateral surgery)

LR resection

9 10

Table 4.5. Suggested surgical guidelines for unilateral recession surgery to treat esotropia and exotropia. (ET Esotropia, LR lateral rectus, MR medial rectus, XT exotropia) Unilateral recession

XT

LR recession

MR resection

ET

MR recession

15

4

3

10

5

20

5

4

15

5.5

25

6

5

20

6

30

7

6

25

6.5

35

7.5

6.5

XT

LR recession

40

8

7

15

7

20

8

25

9

Table 4.6. Suggested surgical guidelines for treatment of vertical deviations. There are two commonly used guidelines. (LR Lateral rectus, PD prism diopters, SR superior rectus) Vertical deviations Guideline 1

1 mm recession = 3 PD correction (approximately) or

Guideline 2

Recess the SR ­according to guidelines for ­unilateral LR recession

 

for unilateral surgery on two rectus muscles to treat esotropia and exotropia are provided in Tables 4.3 and 4.4, respectively. Recession surgery on a single rectus muscle to treat esotropia and exotropia is less commonly performed (>Table 4.5). Two general guidelines are often suggested for determining the surgical dose for vertical strabismus (>Table 4.6). Surgery can be based on the ratio of approximately 3 PD of correction for each millimeter of recession or resection performed. Alternatively, recession of the superior rectus may be performed according to guidelines for unilateral lateral rectus recession. Surgical guidelines for treatment of nystagmus are available in Table 3.3.

4.3 Special Considerations 4.3.1 Torsion Some forms of strabismus require special attention because they are not routine and a surgical plan tailored to a unique situation is required. Patients with torsional diplopia require a surgical plan specifically designed to threat the torsional component of their strabismus, or the procedure is not likely to be successful. Often the most difficult part of this process is identifying the presence of torsion. Once identified, treatment of the torsion is usually best accomplished by surgical manipulation of an oblique muscle. Nasal or temporal offset of the rectus muscles may be of value in some cases (Chapter 15).

4.3.2 Incomitant Strabismus Restrictive strabismus is another form of strabismus that dictates surgery on specific muscles. In these cases, the restriction must usually be improved in order to achieve an optimal outcome. Identifying the nature of the restriction is imperative to the optimal treatment of these patients. Identifying other causes of incomitant strabismus during the evaluation process is also important. Proper identification of these problems allows the strabismus surgeon to devise a plan that not only aligns the eyes in primary position but increases the area of single binocular vision to the greatest extent possible. Patients with a complete or nearly complete paralysis of one or more eye muscles often require a transposition procedure. In addi-

4.4  Adjustable Suture Surgery

tion, if the antagonist of the paralytic muscle has contracted, release of this restriction may be necessary as well.

4.4 Adjustable Suture Surgery Many strabismus surgeons utilize adjustable suture techniques for both complex and routine surgical cases. While some surgeons heavily rely on their use, others do not use them at all. Adjustable sutures may give a strabismus surgeon a “second chance” when the initial postoperative alignment appears to be undesirable. However, it is also possible that adjustment in the early postoperative period may alter other factors that exist that would have led to a good end result. Not infrequently, we have performed surgery on patients without the use of adjustable sutures and have been concerned about a large initial overcorrection in the early postoperative period only to discover that the patient obtained excellent alignment several weeks later. We question what the outcome would have been in such cases had the patient undergone early adjustment. It should be noted that no published study has shown that adjustable suture surgery provides superior results to conventional strabismus surgery. Considering the variable and complex nature of the patients often treated, it is unlikely that such a study will ever be performed to the satisfaction of both the surgeons that employ their use and those who do not. Given this reality, it is up to the individual strabismus surgeon to make a decision regarding the use of adjustable sutures based upon his/her own experience, preference, and patient population.

References 1. 2. 3.

4.

Marlow FW (1920) Prolonged monocular occlusion as a test for the muscle balance. Trans Am Ophthalmol Soc 18:275–290 Kushner BJ, Morton GV (1998) Distance/near differences in intermittent exotropia. Arch Ophthalmol 116:478–486 Olitsky SE (1998) Early and late postoperative alignment following unilateral lateral rectus recession for intermittent exotropia. J Pediatr Ophthalmol Strabismus 35:146–148 Olitsky SE, Kelly C, Lee H, Nelson LB (2001) Unilateral rectus resection in the treatment of undercorrected or recurrent strabismus. J Pediatr Ophthalmol Strabismus 38:349–353

39

Chapter

Preoperative and Postoperative Care

5

5 The primary objective of the surgical management of strabismus is to achieve the desired result while avoiding complications. Preoperative and postoperative care of the strabismus patient are important components of surgical management. Individual practice patterns that evolve to help achieve these goals often do not have firm scientific rationale. A definitive answer for many important questions is often not available in the literature. This may be because adequate prospective or even retrospective analyses of complications is difficult due to the relative rarity of a complication or the fact that more compelling studies are only indirectly related to the particular complication. For example, data confirming that preoperative antibiotics administration reduces conjunctival flora are sometimes used to justify their use in an attempt to decrease the incidence of postoperative infection, though there is no sound scientific evidence that this is the case. Faced with anecdotal evidence, long-term retrospective data with great procedural variability, indirect conclusions, or in many cases simply a lack of data, it is not surprising that preoperative and postoperative management protocols vary significantly among strabismus surgeons. Olitsky and coworkers [1] surveyed a large number of strabismus surgeons on this issue. They found that some trends exist, but they did not find enough agreement among survey respondents to indicate that specific and accepted “standards of care” exist. Specific recommendations and the data to support them, where available, are provided in detail throughout this textbook. This chapter will briefly summarize some of the common concerns regarding the perioperative care of the strabismus patient based upon our personal practice patterns, discussions with other strabismus surgeons and scientific data, where available. The reader will be directed to the appropriate chapter for further information when indicated.

5.1 Scheduling Surgery Opinions differ with regard to the timing of surgical scheduling. Some strabismus surgeons prefer to wait to schedule surgery until they have had a chance to examine the patient at least twice and have collected similar measurements on each of these visits. Other surgeons believe that more than a single visit is helpful to develop a rapport with the patient and/or family,

which may be beneficial in the event of an unexpected or undesirable outcome following surgery. While these concerns seem reasonable, we generally feel comfortable offering surgery to a patient after the first visit if there is no need for refractive error correction, treatment of amblyopia or other conditions, and if reliable strabismus measurement can be obtained. In the absence of such factors, additional visits seem to provide little, if any, supplementary information, and require more time away from home, school and/or work for the patients and family involved. Such visits seem to us to represent inefficient use of office time and are generally a waste of scarce healthcare resources. There is little evidence that short-term fluctuations exist in the degree of strabismus that is measured from one visit to another. Ing [2] followed 41 patients with congenital esotropia. Approximately 50% of these children demonstrated an increase in their deviation by an average of 20 prism diopters. However, these patients were followed for an average of 3 months. We generally operate on patients shortly after they have been scheduled and will obtain new measurements if surgery is delayed. A small majority (56%) of strabismus surgeons who responded to our survey reported that they will schedule surgery after the initial visit [1]. Once surgery is scheduled, an informational handout written layman’s language can be very helpful in further educating patients and parents. Information that may be helpful to include in a handout includes the place, time and date of surgery, the time and date of the preoperative visit (if needed), and the time to arrive for surgery. Fasting instructions can also be included as a reference (>Fig. 5.1).

5.2 Preparation for Surgery Prior to surgery, several important procedures need to take place. The patient must sign a consent or request for surgery form after a discussion with the surgeon and his/her staff. It is expected that the physician has provided informed consent regarding the planned procedure at the time surgery was discussed. Some surgeons will obtain consent at the time that the surgery is recommended, while others will wait until the day of surgery to obtain formal consent for surgery. The medicolegal aspects of informed and written consent are discussed in Chap. 32.

42

Preoperative and Postoperative Care

Chapter 5

Patient information for strabismus surgery Surgeon__________________ Your child has an appointment for eye surgery Pre Op Visit Date/Time:__________________________ Surgery Date/ Arrival Time:_______________________ Post Op Visit Date/Time:__________________________ Place of Surgery:________________________________ It is important that you arrive ON TIME for your surgery. If you are late, surgery may need to be rescheduled depending on the level of operating room availability. The length of surgical procedure is variable and not always predictable, so please be patient on the day of surgery. Plan on being at the hospital for at least a half-day. During surgery, we will make your child as comfortable as possible. Please feel free to ask your doctor(s) and hospital staff members questions at any time. Please follow the food/drink guidelines below exactly. Food/Drink Guidelines

6 hours before

4 hours before

2 hours before

Solid food, formula and milk

Yes

No

No

Breast milk only

Yes

Yes

No

Clear liquids

Yes

Yes

Yes

6 hours before

4 hours before

2 hours before

 

It is very important that you follow these food and drink guidelines before surgery. Clear liquids include water or apple juice. Your child‘s surgery will need to be canceled or delayed if these important instructions are not followed. Fig. 5.1. Preoperative surgical handout

The patient must also be evaluated and prepared for anesthesia. This includes providing instructions on preoperative fasting. The need and procedural protocols for preanesthesia consultation vary according to regional and individual practice patterns. Anesthesia considerations are covered in detail in Chap. 6. In most institutions, the operative site must be marked by a member of the operating team before the patient can be brought into the operating room. We choose to mark the surgical site with the surgeon’s initials and sometimes indicate what type of surgery is to be performed in order to provide an additional measure of safety to protect against wrong-site surgery or the wrong procedure being performed.

5.3 Arrival in the Operating Room Once the patient arrives in the operating room, the patient identity and the planned procedure are confirmed among the operating room staff in a time out. We will often verify the procedure again just prior to initiation of surgery. Following induction of anesthesia, we place a drop of 2.5% phenylephrine hydrochloride in each eye. This constricts the conjunctiva blood vessels and helps to minimize bleeding from the conjunctiva during surgery. It also dilates the pupil to allow prompt examination of the fundus should a deep needle pass or perforation be suspected during surgery. The patient is then prepped and draped in a sterile fashion (Chap. 7). During this preparation, a drop of 5% povidone-iodine is instilled in both eyes (see below).

 

5.4 Care of the Patient Following Surgery Many patients undergoing strabismus surgery will experience at least some nausea following their procedure. While no single medication or treatment protocol has been shown to be universally effective in reducing the incidence of nausea and vomiting following strabismus surgery, some measures may be useful. These measures are covered in detail in chapters on anesthesia considerations (Chap. 6) and anesthesia complications (Chap. 28).

5.5 Timing of the First Postsurgical Visit No consensus exists as to the best timing for the first postsurgical evaluation of the strabismus patient. When asked when they perform the first postoperative exam, 353 strabismus surgeons replied as follows: day 1 (39.1%), days 2–4 (36.4%), 1 week (20.4%), 3–4 weeks (3.2%) and greater than 1 month (0.9%). The two important issues that are evaluated during this time are the initial surgical result and an assessment for postoperative complications, such as slipped muscles, cellulitis, abscess formation, and endophthalmitis. Although endophthalmitis typically is not noted until the second to fourth postoperative day, the range of onset of serious infections is impressively wide, and has been reported as early as 1 day and as late as 30 days after surgery [3, 4] (Chap. 22). Thus there is not an optimal time to for the first postoperative examination that will allow detection of all cases of endophthalmitis. Furthermore, since most surgeons do not make decisions regarding further treatment of over- and under-corrections immediately after surgery, an examination during the early days after surgery provides little useful information.

5.6  Preoperative and Postoperative Drops

Instead, the timing of the first postoperative examination should be tailored to the individual patient and the surgery performed. More important than the timing of this examination is careful review of the signs and symptoms of potential postoperative complications and availability of the operating surgeon, or their designate, during this time period. This information should be provided to the patient and/or family prior to discharge from the surgery unit (>Figs. 5.2, 5.3).

5.6 Preoperative and Postoperative Drops Olitsky and co-workers [1] found the use of preoperative and postoperative medications to be highly variable. In their survey, 5% of respondents reported that they used antibiotic drops before the day of surgery, while 6.7% instilled an antibiotic at the time of surgery, and 54.7% placed topical 5% povidoneiodine solution in the conjunctival fornices during surgical preparation. Postoperatively, 74.2% of respondents instilled an antibiotic at the end of the case and 64.7% had the patient use antibiotic drops at home. Among those who used antibiotics, 93.5% added a topical steroid, usually in a combination preparation. Oral antibiotics were used routinely by only 5.6%. We utilize 5% povidone-iodine solution as part of our routine surgical preparation and place a drop of this solution in the conjunctival fornices during the sterile preparation of the eyes for surgery. We instill a second drop of this solution at the conclusion of the procedure. The literature supports the effectiveness of this agent in considerably reducing the normal conjunctival bacterial flora [5–7]. It has also been shown to reduce the incidence of endophthalmitis in patients undergoing cataract surgery [8]. Although extrapolating these data to include strabismus surgery may not be accurate, we feel that the cost and the risk-to-benefit of taking this precaution is reasonable.

Patient information after eye muscle surgery (children) What to expect on the day of surgery Anesthesia Most children remain sleepy on the day of surgery after anesthesia. Nausea and vomiting Anesthetic agents and eye muscle surgery combined can produce nausea and vomiting. Your anesthesiologist may give your child special medicine to reduce nausea and vomiting. Mild nausea and vomiting is common on the day of surgery and sometimes even on the morning after surgery. If your child has more severe nausea and vomiting, to the point where you do not believe your child is keeping down enough fluids, additional medicine may be needed. A prescription for nausea medication may have been given to you if your child is older than two years. If you didn’t receive this medicine and nausea and vomiting are a problem, please contact your surgeon. Eye pain Eye pain is common after eye muscle surgery, but is rarely severe. Typically, the discomfort can be easily controlled with Children’s Tylenol® or Motrin® in the dosage recommended on the package. It is not uncommon for a child to not want to open his or her eyes on the day of surgery. Do not let this frighten you. Children almost always open their eyes by the next day. Fig. 5.2. Postoperative surgical handout (child)

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Preoperative and Postoperative Care

Chapter 5

Discharge A few bloody tears for the first few days after surgery may occur. Watery discharge is more common. Use a fresh tissue each time to wipe away these tears. Postoperative medications You may have been given a prescription for eye drops or ointment. If so, the medication should be used as directed in the operated eye(s) until the first postoperative appointment or one week. Diet Because of nausea and vomiting which may occur after surgery, we recommend you to advance your child’s diet from clear liquids to solid foods gradually over several hours. When your child is interested in taking something by mouth, offer clear liquids first. Clear liquids might include apple juice or clear soda as well as Popsicles® or Jell-O®.

After surgery The first day after surgery, most children resume normal activity level. Younger children may recover more quickly then older children. Tylenol® may still be needed for discomfort. Light sensitivity is also expected in the first few days after surgery and playing indoors in a clean environment during these days is safest. Reduced activity and increased sleepiness starting several days after surgery is not normal. Contact your surgeon if this occurs. Your child may bathe the day of surgery. Soap and water will not damage the eyes, but may sting the eyes. Try to avoid getting soap and water in the eyes. Look at the eyes Examine your child’s eyes each day after surgery. The first day is usually the worst day for eye redness, lid swelling and discharge. All these symptoms should improve each day after the first postoperative day. Eye redness The eyes will be red where the surgery takes place. The rest of the eye is usually white and should stay white. Sometimes, however, the redness can shift with gravity to another area of the eye. Please contact your surgeon if you are concerned. Lid swelling Lid swelling is usually mild and is seen most often right after awakening during the first few days after surgery. Lid swelling should improve after the child is awake and upright. At no time should the lids get more swollen or red during the day. (This is a warning sign for possible infection and you should call our office.) Discharge The discharge your child experiences should be mild, mainly watery or mucus-like. There may be crust and more thick mucus on awakening in the morning or after a nap. This is normal. However, at no time should your child be producing green or puslike drainage throughout the day. (Should this occur, it may be a warning sign for infection and you should call our office.)

Tips for getting medications in your child’s eyes Drops If you are giving eye drops, either lay your child down and allow the drop to fall on the eye or pull the lower lid down, creating a pocket, and instill one or two drops in this pocket. The eye only holds one drop so a second drop is not needed. Instill a second drop if you think you did not get the first drop in the eye. Applying more than one drop will not harm the eye. Ointment can be applied the same way, by pulling the lower lid down, creating a pocket, and instilling a pea-sized amount of the ointment in this pocket. The eye can only hold a small amount of ointment and any excess will naturally fall out of the eye. If you have any questions or problems, feel free to call us during the day at ______________ or night at _______________. Your doctor may provide additional contact numbers. Fig. 5.2. (Continued) Postoperative surgical handout (child)

 

5.6  Preoperative and Postoperative Drops

Patient information after eye muscle surgery (adults) What to expect on the day of surgery Anesthesia If you received general anesthesia, you may remain sleepy on the day of surgery. Eye pain Eye pain is common after eye muscle surgery, but is rarely severe. Typically, the discomfort can be easily controlled with Tylenol®. You may also be given a prescription for pain medicine. Discharge A few bloody tears for the first few days after surgery may occur. Watery discharge is more common. Use a fresh tissue each time to wipe away these tears. Postoperative medications You may have been given a prescription for eye drops or ointment. If so, the medication should be used as directed in the operated eye(s) until the first postoperative appointment or one week.

After surgery Activity The first day after surgery, you may resume a relatively normal activity level. Light sensitivity is expected in the first few days after surgery. Going outdoors is safe. Do not work or drive on the day of surgery. You may resume work and driving when you feel safe to do so thereafter. If you have double vision, you should avoid driving and avoid other dangerous activities. You may bathe on the day of surgery thereafter. Soap and water will not damage the eyes, but may sting the eyes, so try to avoid getting soap and water in the eyes. Look at the eyes Examine your eyes each day after surgery. The first day is usually the worst day for eye redness, lid swelling and discharge. All these symptoms should improve each day after the first postoperative day. Eye redness The eyes will be red where the surgery takes place. The rest of the eye is usually white and should stay white. Sometimes, however, the redness can shift with gravity to another area of the eyeball. Double Vision Many patients experience double vision after surgery. It is usually temporary. Lid swelling Lid swelling is usually mild and is seen most often right after awakening. Lid swelling should improve as you become awake and upright. At no time should the lids get more swollen or red during the day. (This is a warning sign for possible infection and you should call our office.) Discharge The discharge experienced should be mild; mainly watery or mucus-like. There may be crust and more thick mucus on awakening in the morning or after a nap. This is normal. However, at no time should you be producing green or pus-like drainage throughout the day. (Should this occur, it may be a warning sign for infection and you should call our office.) If you have any questions or problems, feel free to call us during the day at _______________ or night at ______________. Your doctor may provide additional contact numbers. Fig. 5.3. Postoperative surgical handout (adult)

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Preoperative and Postoperative Care

References 1.

2. 3.

4.

Olitsky SE, Awner S, Reynolds JD (1997) Perioperative care of the strabismus patient. J Pediatr Ophthalmol Strabismus 34:126–128 Ing MR (1996) Progressive increase in the quantity of deviation in congenital esotropia. Ophthalmic Surg Lasers 27:612–617 Kivlin JD, Wilson ME Jr. (1995) Periocular infection after strabismus surgery. The Periocular Infection Study Group. J Pediatr Ophthalmol Strabismus 32:42–49 Folk E (1990) Antibiotics and timing of follow-up visits in routine postoperative care: a survey of 25 strabismus surgeons. Binocular Vision Eye Muscle Surg Q 5:7

Chapter 5 5.

6.

7. 8. 9.

Isenberg SJ, Apt L, Yoshimori R, Khwarg S (1985) Chemical preparation of the eye in ophthalmic surgery. IV. Comparison of povidone-iodine on the conjunctiva with a prophylactic antibiotic. Arch Ophthalmol 103:1340–1342 Apt L, Isenberg S, Yoshimori R, Paez JH (1984) Chemical preparation of the eye in ophthalmic surgery. III. Effect of povidoneiodine on the conjunctiva. Arch Ophthalmol 102:728–729 Apt L, Isenberg SJ, Yoshimori R (1985) Antimicrobial preparation of the eye for surgery. J Hosp Infect 6 [Suppl A]:163–172 Speaker MG, Menikoff JA (1991) Prophylaxis of endophthalmitis with topical povidone-iodine. Ophthalmology 98:1769–1775 Wortham ET, Anandakrishnan I, Kraft SP, Smith D, Morin JD (1990) Are antibiotic-steroid drops necessary following strabismus surgery? A prospective, randomized, masked trial. J Pediatr Ophthalmol Strabismus 27:205–207

Chapter

Anesthesia Considerations

6

6 Most strabismus surgery is performed in an outpatient setting. The choice of anesthesia modality is dependent upon one or more of the following factors: patient preference, surgeon preferences, nature of the operation planned, health of the patient, and the recommendations of the anesthesiologist. No single anesthesia modality universally applies to all patients in all situations. In our experience, all children, and even most young adults require general anesthesia, because they usually are unable to tolerate surgical manipulation under local anesthesia. The anesthesia modalities that will be discussed in this chapter include general anesthesia, retrobulbar and peribulbar anesthesia, and topical anesthesia. The final decisions on the anesthesia modality to be used and indeed on evaluation of the patient’s general health, and the decision on proceeding with surgery are, in the final analysis, made by the anesthesiologist. We have made it a policy never to argue or disagree with an anesthesiologist who feels our patient is not healthy enough to undergo a procedure, recognizing that the anesthesiologist often has a far more complex situation on his/her hands in maintaining cardiopulmonary function than does the strabismus surgeon.

6.1 Preoperative Preparation 6.1.1 Laboratory Testing Some centers require a separate preoperative visit with the anesthesiologist prior to the day of surgery, while others utilize telephone screening and day of surgery evaluation by the surgical staff and anesthesiologist satisfactorily. Preoperative laboratory and other testing may be indicated for several reasons, including: (1) identifying a disorder that may affect perioperative anesthetic care, (2) determining the status of an already known disorder, disease, or therapy which may affect perioperative anesthetic care, and (3) formulation of plans and alternatives for perioperative anesthetic care. Routine laboratory testing or diagnostic screening is not necessary for preanesthetic evaluation of patients undergoing strabismus surgery. Identification of specific clinical indicators such as age, pre-existing disease, and magnitude of the surgical procedure planned helps to determine the need for presurgical testing in selected patients.

(Source: American Society of Anesthesiologists http://www. asahq.org/publicationsAndServices/standards/28.pdf accessed 14 April, 2006.)

6.1.2 Fasting Recommendations One of the most serious complications of general anesthesia is aspiration of particulate matter from the stomach into the pulmonary system. To reduce the risk of aspiration, patients are asked to fast for a period of time prior to surgery. One exception is that vital medications may be taken on the morning of surgery with a small sip of water. Children who must take medications with applesauce or some other semisolid food should generally avoid taking the medications, if possible. When practical, medication should be given 6 hours preoperatively or held until the patient is in the recovery room. These suggestions do not apply to nonessential medications such as vitamins and nutritional supplements, which should not be taken. Fasting for adult patients is generally recommended for 6–8 h prior to surgery. Gastric emptying times in infants and children suggest emptying half-times of 50–70 min for formula and 25–50 min for breast milk. A simple rule to remember is 2 h (for clear liquids), 4 h (for breast milk), and 6 h (for everything else, including formula). An 8-h fast should be considered following meals that contain substantial amounts of fried or fatty foods or meats, as these items can prolong gastric emptying. Table 6.1 summarizes these fasting recommendations for children. (Source: American Society of Anesthesiologists http://www.asahq.org/publicationsAndServices/NPO.pdf, accessed 14 April, 2006.) Table 6.1. Recommended schedule for cessation of oral intake for children undergoing surgery Type of oral intake

Fasting schedule

Clear liquids

2 h

Breast milk

4 h

Formula or light meal

6 h

Fatty meal

8 h

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Anesthesia Considerations

6.1.3 Preoperative Medications Routine use of preoperative sedatives is not necessary. Preoperative medications are reasonable, however, for the child or adult patient who is particularly apprehensive prior to surgery. Children who need preoperative sedation may be given midazolam orally as a flavored cocktail. This preparation is administered 10–15 min prior to surgery. Apprehensive adult patients can be premedicated with agents such as midazolam or diazepam.

6.2 General Anesthesia

Chapter 6

While some anesthesiologists prefer to initiate an intravenous line prior to induction of anesthesia in children, we find this practice to be so distressing to children that our standard protocol involves induction of anesthesia with an inhalational agent followed by placement of an intravenous line. Once venous access has been obtained, the patient then undergoes endotracheal intubation or placement of a laryngeal mask for continuation of inhalational anesthesia. The techniques of induction, maintenance, and reversal of anesthesia are left entirely to the discretion of the anesthesiologist. In some centers, parents are encouraged to be in the operating room during anesthesia induction. In others this practice is discouraged. In general, we find this to be unnecessary for the child undergoing anesthesia. However, we have found that many times this process is calming to anxious parents.

General endotracheal anesthesia is probably still the most common anesthesia modality used to facilitate strabismus surgery. It is used for virtually all children and for many adult patients undergoing strabismus surgery. Induction of general anesthesia can be achieved through inhalation of inhalational agents such as nitrous oxide or sevoflurane or through intravenous administration of agents such as propofol. An anesthesiologist or certified nurse anesthetist should be present throughout the procedure. Many patients and families fear complications of general anesthesia more than they fear strabismus surgery itself. In a healthy patient undergoing routine strabismus surgery, excessive fears of complications associated general anesthesia are unfounded. While complications, even serious complications, can occur in association with general anesthesia, serious complications are exceedingly rare. A discussion with the ophthalmologist and anesthesiologist can have an important calming effect on patients and families preoperatively.

6.2.1 Induction of Anesthesia Once in the operating suite, anesthesia can be induced through administration of an inhalational or intravenous agent. In adult patients, an intravenous line is usually started preoperatively, typically in a preoperative holding area. This facilitates administration of anesthetic agents intravenously with rapid induction of anesthesia followed by endotracheal intubation or placement of a laryngeal mask (>Fig. 6.1) to administer oxygen and additional inhalational agents as needed to accomplish surgery. Preformed tracheal tubes are an excellent alternative during strabismus surgery. Preformed tracheal tubes (>Fig. 6.2) direct the tube away from the surgical field, reducing the risk that the tube will be dislodged during surgery and improving access to the tube by the anesthesiologist. A laryngeal mask can be advantageous in children with difficult airways. They are especially useful for short procedures and have the added advantage of being less stimulating to the airway and requiring lower concentrations of halogenated agents for insertion compared to endotracheal tubes [1]. Additionally, muscle relaxants can be avoided, extubation is usually less stressful, and the airway more comfortable following extubation.

Fig. 6.1. Laryngeal mask airway, cuffed endotracheal tube, and uncuffed endotracheal tube

Fig. 6.2. A preformed endotracheal tube has the advantage of being directed away from the surgical field

 

6.3 Retrobulbar and Peribulbar Anesthesia It is important from the point of view of strabismus surgery to have an understanding of the anatomy relevant to ophthalmic anesthesia. This allows the surgeon to target the block to the most essential areas of the eye and/or orbit. Sensory fibers from the globe and orbit are carried by the trigeminal nerve, which has three divisions: ophthalmic, maxillary, and mandibular. The majority of the sensory fibers from the eye and ocular adnexa are carried by the ophthalmic division. The ophthalmic nerve has three divisions of its own: frontal, lacrimal, and nasociliary. The frontal nerve has at least two subdivisions which include the supraorbital nerve (carrying sensation from the conjunctiva and skin of the central upper lid) and the supratrochlear nerve, which carries sensation from the medial onethird of the upper lid. The lacrimal subdivision carries sensory fibers from the skin and conjunctiva of the lateral portion of the upper eyelid. The nasociliary nerve carries sensory fibers from the cornea, iris, ciliary body, peribulbar conjunctiva, and the optic nerve sheath. Its fibers pass through the ciliary ganglion. The infratrochlear branch of the nasociliary nerve is responsible for sensation from the medial canthus, medial portion of the lower skin, conjunctiva, caruncle, lacrimal sac, and canaliculi. Motor input to the extraocular muscles comes from the oculomotor, trochlear, and abducens nerves. The oculomotor nerve supplies motor fibers to the superior rectus, medial rectus, inferior rectus, inferior oblique muscles and the levator palpebrae superioris muscle in the upper eyelid. It enters the orbit through the superior orbital fissure and splits into a superior and inferior division. The superior division innervates the superior rectus and the levator muscles. The trochlear nerve supplies motor fibers to the superior oblique muscle. It enters through the superior orbital fissure above the annulus of Zinn. Anesthetic delivered into the muscle cone would therefore not be expected to provide significant akinesia of the superior oblique muscle. The abducens nerve enters the orbit through the superior orbital fissure to innervate the lateral rectus muscle. Retrobulbar and/or peribulbar anesthesia is an excellent option for cooperative adult patients who feel that they can comfortably tolerate surgery under local anesthesia with or without concurrent sedation. The term retrobulbar anesthesia is used here to refer to both retrobulbar and peribulbar anesthesia. It is often a preferred modality of anesthesia administration for the adult patient undergoing routine monocular strabismus surgery because of its safety, simplicity, and speed of recovery. Patients who have undergone strabismus surgery under retrobulbar anesthesia have very few systemic complaints following surgery and are generally very comfortable. Retrobulbar anesthesia may also be utilized in a patient who is undergoing bilateral surgery in which the eye undergoing the most complex procedure receives a retrobulbar block and the eye undergoing the less complex procedure receives topical anesthesia as described below. Effective use of retrobulbar anesthesia requires several prerequisites, including a physician proficient in the administration of retrobulbar anesthesia, a skilled surgeon, and a care-

6.5  Topical Anesthesia

fully planned procedure. An inadequate retrobulbar block can be associated with significant residual pain and discomfort during surgery that may be intolerable to the patient. Even an excellent retrobulbar block may be associated with a sensation of deep pressure during traction on the extraocular muscle. A less experienced strabismus surgeon may wish to consider strabismus surgery under general anesthesia in appropriate patients to avoid these problems. Surgery on the inferior oblique muscle is often associated with intraoperative discomfort despite an excellent retrobulbar block and surgeons not proficient in the techniques of inferior oblique surgery may wish to consider general anesthesia as an alternative. One disadvantage of retrobulbar anesthesia is tissue distortion that can occur as the anesthetic agent migrates anteriorly, hydrating the anterior Tenon’s capsule, with resultant swelling of this tissue. While relatively easy to manage for the experienced surgeon, tissue and landmark distortion can confuse less experienced surgeons. Retrobulbar anesthesia may be supplemented with intravenous sedation administered by the anesthesiologist as deemed necessary during the case, titrated by continuous communication between the operative team and the patient. Topical anesthetic drops can be a useful adjunct to supplement retrobulbar anesthesia especially during the latter stages of the case when the effect of retrobulbar anesthesia on the conjunctiva often begins to wane. A variety of anesthetic agents can be used. A common combination is bupivacaine 0.5%–0.75% and lidocaine 2% without epinephrine in a 50/50 mixture. Using a retrobulbar needle, 3–5 ml of this mixture is injected into the retrobulbar or peribulbar space. Because retrobulbar injection of an anesthetic agent can be very painful, brief administration of intravenous sedatives can facilitate administration of retrobulbar anesthesia. Potential complications of retrobulbar anesthesia, reviewed in Chap. 28, include retrobulbar hemorrhage, penetration of the globe, intramuscular injection, trauma to the optic nerve, and stimulation of the oculocardiac reflex.

6.4 Sub-Tenon’s Anesthesia Tenon’s capsule is an anterior extension of the dura covering the optic nerve. Mein and Woodcock [2] described the use of sub-Tenon’s anesthesia for use in cataract and vitreoretinal surgery. Capo and Munoz [3] later described its use in strabismus surgery. Anesthesia develops rapidly after administration of the anesthetic agent and akinesia follows after 4–5 min. The technique results in blockage of all three branches of the ophthalmic division of the trigeminal nerve providing an excellent superior sensory block. We have found the technique to be an excellent alternative for both routine and complicated strabismus cases.

6.5 Topical Anesthesia The concept of topical anesthesia for strabismus surgery is a misnomer. While an occasional patient can tolerate strabismus

49

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Anesthesia Considerations

surgery with topical anesthesia alone, such patients are uncommon and most require at least mild to moderate sedation in order to comfortably tolerate surgery. The prerequisites for using topical anesthesia with intravenous sedation include a skilled, gentle surgeon, and an anesthesiologist who is skilled at assessing both the patient’s moment-to-moment needs during the procedure and the surgical needs of the surgeon. A comfortable patient is needed during the procedure, but a relatively awake and alert patient is needed near the end of the procedure to facilitate adjustment. Thus careful coordination between the anesthesiologist and surgeon is required in order to effectively manage a patient using topical anesthesia approaches. The indications for strabismus surgery under topical anesthesia are dependent on the judgment and experience of the surgeon and include the desire to assess alignment and make adjustments to the ocular alignment intraoperatively, and the ability to accomplish bilateral surgery on a patient who is not a good candidate for general anesthesia when a sequential retrobulbar injection on different days is not feasible. Complex strabismus surgery and surgery on oblique muscles is not easy to perform under topical anesthesia because it is often associated with significant patient discomfort, and therefore is rarely done. Exposure of the surgical site can be so compromised by modifications in surgical technique required because of use of topical anesthesia that the technique is not universally applicable to all patients. Concurrent sedation that is administered to supplement topical anesthesia is directed by the anesthesiologist and guided by the ophthalmologist in conjunction with the patient. Effective use of the technique requires careful coordination between the ophthalmologist and anesthesiologist to effectively time the administration and withdrawal of the sedative agents and requires careful and detailed explanation to the patient preoperatively with continuous intraoperative communication. The surgeon should have a backup plan to manage the occasional patient who, despite favorable assessment preoperatively, turns out not to be able tolerate surgery under topical anesthesia. Options include conversion to retrobulbar or sub-Tenon’s anesthesia, conversion to general anesthesia, or deferring surgery to another day. The preoperative systemic evaluation should be tailored to the backup plan, unless the surgeon is willing to postpone surgery to another day. For example, if general anesthesia is the backup plan for a patient undergoing planned strabismus surgery under topical anesthesia, preoperative assessment should be sufficient to clear the patient for general anesthesia.

Fig. 6.3a,b. Operating “in the hole” with less exposure is often required for surgery performed under topical anesthesia with sedation (a), compared to the greater exposure allowed under general anesthesia (b)

Chapter 6

6.5.1 Modification of Surgical Technique for Topical Anesthesia The surgeon must be willing and able to significantly modify his/her usual surgical technique in order to comfortably perform strabismus surgery under topical anesthesia. The procedure must be done with less exposure of the surgical site, minimization of cautery, and minimized traction on the extraocular muscles. It is often necessary to operate “in the hole” (>Fig. 6.3). Exposure of the muscle is facilitated by retropulsion of the globe and mild traction compared to the more direct traction and anterior displacement of the globe that is used during standard strabismus surgery. Surgery under local anesthesia can be stressful to some patients. Conversation in the operating room often must be kept to a minimum to reduce patient anxiety. The operating team should control conversation and avoid such terms as “oops,” “oh no,” and similar phrases that can have a negative connotation and be alarming to patients. Additionally, avoiding open discussion about scissors, knives, hooks, and other surgical tools is recommended. Referring to surgical equipment by its name rather than function may reduce patient anxiety. A request for the “Westcott’s” rather “Westcott scissors,” for example, may be less of a concern to the patient undergoing surgery.

 

6.6 Postoperative Nausea and Vomiting The most common problems that occur in the recovery room following pediatric anesthesia include nausea, vomiting, restlessness, and pain [4]. The incidence of postoperative nausea and vomiting following strabismus surgery is high, affecting as many as 30%–70% of patients [5–8]. Nausea and vomiting frequently occur on the way home from the operating suite or several hours following surgery after the patient has returned home. Postoperative nausea and vomiting is usually limited in duration, but can occasionally be prolonged, extending to the following day. Eberhart and coworkers [9] identified four risk factors among 1257 children undergoing a variety of different surgical procedures in a prospective study. Those four factors included duration of surgery greater than or equal to 30 min, age ≥3 years, strabismus surgery, and a positive history of postoperative nausea and vomiting in the patient or primary relatives. Velez and coworkers [10] reported that nausea and vomiting was more common in the first 24 h after surgery in patients who underwent manipulation of adjustable sutures on the day of surgery compared with patients who underwent adjustment the following day. Despite many attempts to reduce the frequency of nausea and vomiting after strabismus surgery, it remains a problem. Many techniques have been used, sometimes with conflicting results. Chhabra and coworkers [11] reported that peribulbar block with propofol-based anesthesia resulted in a low incidence of nausea and vomiting, reporting that only 2.9% of children undergoing strabismus surgery in their prospective study experienced nausea and vomiting, considerably lower than with other anesthesia techniques they investigated. Another prospective study showed no significant difference in the level of postoperative nausea and vomiting following strabismus surgery performed with retrobulbar anesthesia compared to use of general anesthesia [12]. There are a number of reports in the literature suggesting a variety of preoperative medications to reduce the incidence of postoperative nausea and vomiting. No single pharmacologic agent has been proven to be a panacea. We do not routinely administer antiemetic medications prior to strabismus surgery but instead leave this decision to the anesthesia team. Superhydration administered through perioperative fluid administration was shown in one study to significantly reduce postoperative nausea and vomiting in children undergoing strabismus surgery [13]. Madan and coworkers [14] reported that administration of intravenous dexamethasone (0.25 mg/kg) immediately after induction of anesthesia was effective in reducing postoperative nausea and vomiting in pediatric patients undergoing strabismus surgery. Propofol was shown to reduce the incidence of vomiting following strabismus surgery compared to thiopental/isoflurane anesthesia in one study [15] but was shown in another study to have no significant advantages over halothane/thiopental [16]. Wennstrom and Reinsfelt [17] reported a reduction in postoperative nausea and vomiting in children who received diclofenac administered rectally compared to administration of morphine. In a study by Bowhay

6.6  Postoperative Nausea and Vomiting

51

and coworkers [18] children treated with ondansetron had less than half the risk of vomiting compared to those given placebo. Ketorolac was not shown to offer an advantage compared to placebo in one study [19]. Hand acupressure was reported to reduce postoperative nausea and vomiting after strabismus surgery in one study [20]. The benefits of prophylactic antiemetic therapy have been challenged on the grounds that there are insufficient data available to draw conclusions [21]. A list of possible agents that may be used to prevent and/or reduce postoperative nausea and vomiting is included in Table 6.2. We attempt to reduce the occurrence of postoperative nausea and vomiting through specific measures. We generally try

Table 6.2. Selected agents that may be useful for prevention and/or treatment of postoperative nausea and vomiting Drug (trade name)

Adult dose Pediatric dose

Duration

Use with caution

Droperidol i.m., i.v.: (Inapsine®) 0.625– 1.25 mg (10–20 µg/ kg)

i.m., i.v.: 50–75 µg/ kg

3–4 h

Parkinsonism, hypovolemia

Metoclopramide (Reglan®)

i.m., i.v.: 0.625– 1.25 mg (10–20 µg/ kg)

i.m., i.v.: 50–75 µg/ kg

3–4 h

GI obstruction, seizures, parkinsonism

Ondansetron (Zofran®)

i.v.: 4 mg p.o.: 8–16 mg

i.v.: 0.1 mg/ 4–6 h kg (max dose: 4 mg)

Prometha- i.v., i.m., i.m., i.v., zine (Phen- p.o., rectal: p.o., rectal: ergan®) 12.5–25 mg 0.25–1 mg/ kg

Prochlorperazine (Compazine®)

i.m., i.v., p.o.: 2.5–10 mg Rectal: 10–25 mg

4 h

p.o., rectal, 6–12 h >10 kg: 2.5 mg (max dose: 15 mg/day) i.m., i.v.: 0.1– 0.15 mg/kg per dose (not recommended for Fig. 7.6). B-list instruments might include instruments used occasionally, perhaps in 10% of cases. Rather than

 

7.4  Surgical Instruments

Fig. 7.4. Basic room set up for strabismus surgery

Fig. 7.5. Placement of a single operating room light above the patient’s chest provides excellent lighting for most procedures without the need to manipulate the position of the light during surgery

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Equipment, Supplies, and Preparation

Chapter 7

have B-list instruments crowd the instrument stand, they can be kept on the back table where they are readily available, if needed (>Fig. 7.7). Generally, they do not need to be removed from their storage container unless they are used during surgery. Finally, C-list instruments represent rarely used instruments. These instruments will vary from surgeon to surgeon and may include malleable retractor, special hooks, and special scissors (>Fig. 7.7). These instruments may be kept sterilized in peel packs and other sterile containers in the instrument storage area near the operating room where they can be readily retrieved, if needed.

Specific instruments that comprise the list of instruments commonly and uncommonly used by a particular surgeon are based on personal preference and availability. One surgeon’s favorite instrument might be another surgeon’s least favorite instrument and in most cases there is no clear reason to choose one particular instrument over another. In our experience three instruments are so unique in their design and function that they offer significant advantages not offered by comparable instruments and thus are worth specific elaboration.

Fig. 7.6. A-list instruments that should be available for every case on the instrument stand. This list will vary depending on the personal preferences of the surgeon. From left to right: Green hook (2), Jamison

hook (2), Stevens hook (2), 0.5-mm curved locking forceps (2), Thorpe forceps (2), needle holder, Wescott scissors, caliper, hemostat, and lid speculum (above)

Fig. 7.7. Instruments that might be considered for inclusion on the B-list of occasionally used instruments or the C-list of rarely used instruments. From left to right: malleable retractors (2), #3 knife handle,

double hook, Gass hook, Bishop hook with plate, Scobee hook, Demarres retractor, Conway lid retractor, Birch tendon tucker, Jameson muscle clamp, Fink tendon tucker, Scott ruler, Serrefine clamps (2)

 

7.4.1 Curved Locking 0.5-mm Forceps Locking 0.5-mm forceps are available in a straight and curved design. Both may be used during several important steps in strabismus surgery. The most important application is placement of these forceps on the muscle stump following detachment of the muscle to help manipulate and position the eye and to help with identification of the muscle insertion after the muscle has been detached. The curved version of these forceps offers distinct advantages in that they extend over, rather than rest on, the cornea (>Fig. 7.8). Because of this design feature, these forceps are unlikely to result in damage to the corneal epithelium and they may be allowed to rest on the orbital bones without the need for constant manipulation by the assistant surgeon.

7.4  Surgical Instruments

7.4.2 Gass Muscle Hook Many surgeons prefer to place a traction suture around the lateral rectus muscle for use in positioning the eye during surgery on the inferior oblique muscle. This step has traditionally required blind passage of a large needle between the lateral rectus muscle and sclera, a maneuver that can be dangerous (>Fig. 7.9). A Gass muscle hook has a hole in its toe (>Fig. 7.9) that both simplifies placement of a lateral rectus muscle traction suture and makes the procedure safer. As shown in Fig. 7.9, after passing the Gass muscle hook beneath the lateral rectus muscle, the suture can be passed transconjunctivally through the perforation in the toe of the hook. The hook is then withdrawn, pulling the traction suture around the lateral rectus muscle insertion and avoiding the blind passage of a large needle beneath the lateral rectus muscle.

Fig. 7.8. Curved locking 0.5-mm forceps placed on the muscle stump after detachment of the muscle from the sclera provide excellent control of the eye without touching the cornea

Fig. 7.9a,b. Placement of a traction suture around the lateral rectus muscle to facilitate surgery on the inferior oblique muscle using: a blind passage of a suture, or b using Gass muscle hook. The Gass muscle hook is not only safer, but makes this step easier to accomplish

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Fig. 7.10. Scobee hook after it has been used to engage and isolate the inferior oblique muscle

7.4.3 Scobee Muscle Hook

Chapter 7

Fig. 7.11. Anatomy of a surgical needle

Table 7.1. Ideal characteristics of a surgical needle Made from high-quality stainless steel

A Scobee muscle hook is a superb instrument for hooking the inferior oblique muscle. Use of this muscle hook reduces the tendency to grasp excess adjacent orbital structures, such as orbital fat, and reduces the tendency for the assistant surgeon to lose control of the inferior oblique muscle after it has been isolated on the hook. Manipulation of the inferior oblique muscle is also easer than manipulation with other muscle hooks (>Fig. 7.10).

7.5 Surgical Needles Ideal surgical needle characteristics are listed in Table 7.1. Surgical needles have three basic components including a swage, a body, and a point. The swage is the site of attachment of the suture to the needle. For smaller caliber needles, a hole is drilled in the end of the needle with a laser [6]. The needle is attached to the suture by compressing the walls of the swage against the suture. This results in a smooth swage with low tissue drag force, reducing tissue trauma. Needles are more susceptible to damage in the area of the swage than in other areas. The body of a needle is its longest component. Surgical needles should only be grasped by needle holders on the body of the needle. The body of the needle is critical for interaction with the needle holder and its ability to transmit the penetrating force of the needle to the point. Needle factors that affect performance include needle diameter and radius, body geometry, and the stainless steel alloy from which it is constructed. The important design features of a needle are shown in Fig. 7.11. The cross-sectional area of a surgical needle may be circular, rectangular, triangular, or trapezoidal. The diameter of a needle is the gauge or thickness of the needle wire. Needles used for strabismus surgery have a single radius of curvature. The radius of a needle is the distance from the body of the needle to the center of the circle along which the needle curves. The curvature of a needle with a single radius of curvature may vary

Smallest possible diameter Stable in needle holder Produces minimal tissue trauma Minimal tissue penetration resistance Sterile

between 90° (1/4), 135° (3/8), 180° (1/2), and 225° (5/8). The chord length of a needle is the linear distance from the point of the needle to the swage, and determines the bite width. The length of the needle is the distance measured along the needle from the tip of the point to the swage. The needle length, not chord length, is indicated on suture packaging. The point of a surgical needle varies depending on the surgical application and the tissue to be penetrated. The point of the needle extends from the tip of the needle to the needle body. Most needles used in strabismus surgery have spatula points. These needles, originally designed for ophthalmologic surgery, are flat on the top and bottom surfaces to reduce tissue injury. The cutting edges are on the tip and sides of the point. Spatula needles allow the needles to stay in the tissue plane. They facilitate easy tissue penetration and needle control as they pass between and through tissue layers. The point of the needle may be located on the top or bottom of the needle (>Table 7.2).

7.5.1 Choosing a Surgical Needle Several needles are manufactured for use during ophthalmologic surgery. Each strabismus surgeon should choose his/her needle(s) based upon needle design, performance, and personal preference. From a practical standpoint, larger needles are easier to handle and are easier to see as they pass through the sclera. Their disadvantages include the fact that they are

 

more likely to produce muscle damage when passed through the muscle and there is a tendency to pass larger needles more deeply into the sclera [7], which could increase the risk of sclera perforation (Chap. 21). Smaller caliber needles, in contrast, are more difficult to handle, but are less likely to result in damage to the muscle and they tend to be passed less deeply into the sclera. Goldstein and coworkers [8] evaluated tunnel characteristics of scleral passes based on a histological analysis of 40 needle passes in the sclera of a rabbit model. They reported that a needle with an acute curve produced a shorter pass though similar depth compared with a shallow curve needle. A needle with a cutting surface on its inferior aspect tended to produce a pass that was deeper than a needle with a cutting surface on its superior aspect. All four of the needles highlighted in Table 7.2 are acceptable for strabismus surgery and their use is a matter of surgeon preference. Other needle styles, not reviewed here, may also be useful. Needles used to close the conjunctiva and/or Tenon’s capsule need not meet such precise specifications. These needles are passed through less vital tissue where there is little or no risk of perforations and other serious complications. Nevertheless, needles of small diameter should be used to avoid large holes in the conjunctiva.

7.6  Sutures

7.6 Sutures The perfect suture would have several characteristics as outlined in Table 7.3. Unfortunately, no single suture can meet all of these criteria, thus compromises must be made depending upon the surgical situation. The choice of sutures is based on science as well as individual preferences of the surgeon. Sutures can be constructed from a single filament or multiple filaments, and are known as a monofilament and multifilament sutures, respectively (>Fig. 7.12). Sutures can be classified as absorbable and nonabsorbable. Sutures that undergo degradation in tissues with loss of tensile strength within 60 days are generally considered absorbable while those that maintain tensile strength for longer than 60 days are generally considered nonabsorbable [9]. The first stage of absorption is linear, lasting for several days to weeks. The second stage overlaps the first stage and is characterized by loss of the suture mass. Loss of tensile strength and rate of absorption are separate phenomena.

7.6.1 Absorbable Sutures 7.6.1.1 Collagen Sutures

7.5.2 Use of a Surgical Needle The force required to pass the needle through the ocular tissue should be applied in a direction following the curvature of the needle. If the position of the needle in the ocular tissues requires adjustment, the needle should be removed and reinserted. The surgeon should never attempt to twist or bend the needle while it is engaged in tissue.

Absorbable sutures are usually made from either collagen or synthetic polymers. Collagen sutures are derived from the submucosal lining of ovine small intestine or the serosal layer of bovine small intestine. They are treated with an aldehyde Table 7.3. Ideal suture characteristics Easy to manipulate Minimal or no tissue reaction

Table 7.2. Characteristics of several available and commonly used spatula needles for strabismus surgery Type of needle

S14

S24

S28

TG 100

Does not support bacterial growth High tensile strength Sterile Absence of allergic potential

Cross Section

Absence of carcinogenic potential Absorbed after serving its purpose

Point of needle

Top

Top

Bottom

Top

Curvature (degrees)

112

90

164

97

Chord length (mm)

7.23

7.31

5.28

5.94

Radius (mm)

4.37

5.16

2.67

3.96

Thickness (mm)

0.33

0.33

0.2

0.2 Fig. 7.12. Monofilament and multifilament sutures

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solution which cross-links and strengthens the suture making it more resistant to enzymatic degradation [9]. Suture treated in this way is referred to as plain gut suture [9]. If the suture is treated with chromium trioxide, it becomes chromic gut. Plain gut suture is composed of several plies that have been twisted, machine ground, and polished, producing a smooth surface that is monofilament-like in appearance [9]. The suture absorbs through a process of lysosomal and enzymatic degradation [10]. Collagenase also appears to play a role in degradation of collagen sutures [9]. Plain gut suture is rapidly absorbed, losing its tensile strength after 7–10 days. It can produce marked local tissue reaction. The primary indication for use of plain gut suture in strabismus surgery is as an option in the closure of the conjunctiva. Its rapid degradation minimizes the amount of time that the patient may experience discomfort because of contact of conjunctival-closure suture ends with the eyelids during blinking and eye movements.

7.6.1.2 Synthetic Sutures The development of synthetic sutures was motivated by the desire to have suture that produced less local reaction compared to collagen-based sutures. Sutures made from high-molecularweight polyglycolic acid have been used for strabismus surgery with good success [11]. Sutures with a caliber of 6.0 are most commonly used for strabismus surgery, though some surgeons prefer a 5.0 caliber suture. Two polyglycolic-acid-based sutures are Biosorb-C (Alcon®) and Dexon “S”® (Davis and GeckTM). The use of Biosorb-C and Dexon “S” as a preferred suture for adjustable strabismus surgery done 6–24 h after the completion of surgery has been advocated by some surgeons [12]. Monofilament sutures produced from polyglycolic acid are too stiff for use in surgery. Because of this, the material is extruded into fine filaments which are braided and coated with polycaprolate for surgery [9]. These sutures degrade through hydrolysis of an ester linkage, and maintain tensile strength for 2–3 weeks. Polyglactin 910TM (Vicryl®) is a polymer that is synthesized by the random co-polymerization of two simple hydroxy acids, glycolic acid and lactic acid. Successive monomeric units of glycolic or lactic acid are linked together by ester linkages. It is available braided or as a monofilament, though the braided suture is generally used for strabismus surgery. Polyglactin 910TM has been shown to be useful for extraocular muscle surgery because it retains sufficient strength, has low antigenicity, and is easy to use, especially if it is coated [13]. Sutures with a caliber of 6.0 are most commonly used, though some surgeons prefer 5.0 caliber sutures. Approximately 50% of its tensile strength is retained at 5 days, and mass absorption of the suture is usually complete by 42 days. The suture has high knot security. Polyglactin 910TM is coated with Polyglactin 370 plus calcium stearate, which makes the surface of the suture smoother, thus reducing its coefficient of friction and reducing tissue drag. It is available undyed or violet colored. The latter is usually preferred for strabismus surgery because of enhanced visibility. The suture undergoes hydrolysis in the body to produce its original monomers, glycolic acid and lactic acid. Be-

Chapter 7

cause these two monomers are produced under normal physiologic conditions as byproducts of several metabolic pathways, they produce minimal local reaction and systemic toxicity.

7.7 Nonabsorbable Sutures Nonabsorbable sutures maintain their tensile strength for more than 60 days. Polyester fiber suture (Mersilene®, Ethicon) is the most commonly used nonabsorbable for strabismus surgery. This suture is composed of poly(ethylene terephthalate), which is prepared from fibers of high-molecular-weight, long-chain, linear polyesters. The sutures are braided to optimize handling properties. Mersilene® exhibits a minimal acute tissue inflammatory response. Over time, the suture is encapsulated by fibrous connective tissue. No significant decline in the strength of polyester sutures occurs over time. The suture can become extruded, however, producing unwanted signs and symptoms as outlined in Chap. 19. The most common uses of polyester fiber sutures include posterior fixation sutures and muscle union procedures such the Jensen procedure (Chap. 13). Ludwig [14] has advocated the use of nonabsorbable sutures in the repair of a lengthened, stretched, remodeled scar between an operated muscle tendon and sclera which she believes is a common factor contributing to the variability of outcome after strabismus repair, resulting in overcorrection even years after surgery. She believes that definitive repair requires firm reattachment of tendon to sclera using nonabsorbable sutures (Chap. 23).

7.8 Surgical Gloves In general, powder-free gloves are preferred for ophthalmologic surgery, including strabismus surgery. Starch powdered gloves increase the risk of sterile intraocular and extraocular inflammation [15]. Latex-free gloves should be used for patients who have latex allergy and for those who are susceptible to latex allergies, such as patients with spina bifida [16].

7.9 Magnification The vast majority of strabismus surgeons use magnification in the form of surgical loupes to perform strabismus surgery. Some surgeons use microscope magnification and others prefer no magnification at all. While magnification is not absolutely essential for performing strabismus surgery, it can be very useful when performing critical tasks such as passing needles through the sclera and during tedious dissection. The choice and amount of magnification remain issues of surgeon preference, but in general magnification of 2× to 2.5× is sufficient. Higher degrees of magnification result in a smaller field of view and also are associated with heavier, more bulky surgical loupes. The surgeon should consider a lightweight pair of loupes, which are associated with less surgeon fatigue during

 

surgery. Surgical loupes with integrated optics often provide superior comfort and, in the opinion of many surgeons, superior optics compared to flip down or hand band mounted loupes (>Fig. 7.13). A headlight can be utilized depending on surgeon preference for all or for selected strabismus cases.

References 3.

4.

5. 6.

7.

8. 9.

10.

11.

Fig. 7.13a,b. Surgical loupe styles for magnification during strabismus surgery. a Flip down optics, and b integrated optics

References 1.

2.

Speaker MG, Milch FA, Shah MK, Eisner W, Kreiswirth BN (1991) Role of external bacterial flora in the pathogenesis of acute postoperative endophthalmitis. Ophthalmology 98:639–649; discussion 650 Isenberg SJ, Apt L, Yoshimori R, Khwarg S (1985) Chemical preparation of the eye in ophthalmic surgery. IV. Comparison of povidone-iodine on the conjunctiva with a prophylactic antibiotic. Arch Ophthalmol 103:1340–1342

12. 13.

14. 15.

16.

Isenberg S, Apt L, Yoshimuri R (1983) Chemical preparation of the eye in ophthalmic surgery. I. Effect of conjunctival irrigation. Arch Ophthalmol 101:761–763 Apt L, Isenberg S, Yoshimori R, Paez JH (1984) Chemical preparation of the eye in ophthalmic surgery. III. Effect of povidoneiodine on the conjunctiva. Arch Ophthalmol 102:728–729 Perry LD, Skaggs C (1977) Preoperative topical antibiotics and lash trimming in cataract surgery. Ophthalmic Surg 8:44–48 Ahn LC, Towler MA, McGregor W, Thacker JG, Morgan RF, Edlich RF (1992) Biomechanical performance of laser-drilled and channel taper point needles. J Emerg Med 10:601–606 Hussein MAW, Coats DK, Harris LD, Sanchez CR, Paysse EA. Ultrasound biomicroscopy characteristics of scleral tunnels created with needles commonly used during strabismus surgery. Binocul Vis Ocular Motil Q (in press) Goldstein JH, Prepas SB, Conrad SD (1982) Effect of needle characteristics in strabismus surgery. Arch Ophthalmol 100:617–618 Szarmach RR, Livingston J, Rodeheaver GT, Thacker JG, Edlich RF (2002) An innovative surgical suture and needle evaluation and selection program. J Long Term Eff Med Implants 12:211–229 Salthouse TN, Williams JA, Willigan DA (1969) Relationship of cellular enzyme activity to catgut and collagen suture absorption. Surg Gynecol Obstet 129:691–696 Apt L, Henrick A (1976) “Tissue-drag” with polyglycolic acid (Dexon) and polyglactin 910 (Vicryl) sutures in strabismus surgery. J Pediatr Ophthalmol 13:360–364 Neumann D, Neumann R, Isenberg SJ (1999) A comparison of sutures for adjustable strabismus surgery. J AAPOS 3:91–93 Saunders RA, Helveston EM (1979) Coated Vicryl (polyglactin 910) suture in extraocular muscle surgery. Ophthalmic Surg 10:13–18 Ludwig IH (1999) Scar remodeling after strabismus surgery. Trans Am Ophthalmol Soc 97:583–651 Sellar PW, Sparrow RA (1998) Are ophthalmic surgeons aware that starch powdered surgical gloves are a risk factor in ocular surgery? Int Ophthalmol 22:247–251 Pires G, Morais-Almeida M, Gaspar A et al (2002) Risk factors for latex sensitization in children with spina bifida. Allergol Immunopathol (Madr) 30:5–13

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Chapter

Techniques of Exposure and Closure and Preliminary Steps of Surgery

8

8 In this textbook, we have chosen to emphasize the techniques of exposure of the operative site and closure of the conjunctiva for strabismus surgery in a separate chapter. These techniques are similar for all strabismus operations. Therefore, this chapter describes techniques to isolate and dissect the fascial tissues associated with each of the extraocular muscles, while the techniques required for recession, resection, tucking, and other procedures are described in other chapters, as appropriate. In addition, preliminary steps that are important to perform in many strabismus operations are reviewed in this chapter.

8.1 What to do Prior to Making a Conjunctival Incision for Strabismus Surgery Three important steps are recommended prior to making an incision for strabismus surgery. These steps include: (1) visual inspection of the patient’s conjunctiva to help facilitate later wound closure, (2) forced traction testing of the rectus muscles and/or oblique muscles as needed, and (3) visual and/or tactile identification of the rectus muscle(s). Additionally, the spring back test may be useful if a slipped or lost muscle is suspected preoperatively.

8.1.1 Visual Inspection of the Patient’s Conjunctival Anatomical Landmarks The surgeon should carefully inspect the patient’s conjunctival anatomy prior to making an incision. Inspection may disclose previously undetected defects or lesions of the conjunctiva such as symblepharon, cysts, filtration blebs, evidence of prior surgery, and other lesions. Visual inspection prior to surgery is often the first clue that the patient has undergone previous strabismus surgery, as patients are often unaware of previous surgery, especially if surgery was done in early childhood. Inspection of the medial aspect of the conjunctiva is especially important if surgery will be carried out in this area. Closure complications of the medial conjunctiva such as advancement of the plica semilunaris may be avoided if the surgeon

has inspected this area preoperatively and knows what the area should look like after closure (Chap. 19).

8.1.2 Visual and Tactile Identification of the Rectus Muscles The surgeon is obligated to identify the rectus muscle(s) to be operated and adjacent rectus muscles that may be encountered during surgery before making an incision into the conjunctiva. The rectus muscles are usually easy to identify through two simple techniques. The anterior ciliary vessels readily mark the location of the rectus muscle insertions. As the eye is rotated back and forth with forceps, these vessels can be easily seen in the episcleral space moving beneath the conjunctiva (>Fig. 8.1). While this provides an initial estimation of the position of the rectus muscle insertion, the most effective way to determine the location of the border of a rectus muscle is to palpate it using a blunt object such the heel of a muscle hook. A muscle hook is placed against the conjunctiva approximately 8–10 mm posterior to the limbus in the space between two adjacent rectus muscles. While exerting mild pressure on the hook against the globe, the hook is moved toward the rectus muscle. When contact with the border of the rectus muscle is made, the hook can no longer be advanced and the muscle will become bunched against the hook, clearly identifying its border (>Fig. 8.2).

8.1.3 Rectus Muscle Forced Traction Testing Traction testing should be done when indicated prior to initiation of surgery. Rectus muscle traction testing can be done in the office or in the operating room. In the operating room, traction testing is often performed on both eyes even if only one eye is undergoing surgery. While some surgeons perform traction testing on all patients prior to surgery, others limit traction testing to those with a history of previous surgery and/or the presence of abnormal ductions noted in the office prior to surgery. Traction testing is easy to perform, but can be associated with complications including conjunctival tears, hemorrhage, and corneal abrasion.

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Techniques of Exposure and Closure

Chapter 8

Fig. 8.1. Visual identification of a rectus muscle insertion by observation of the anterior ciliary vessels in the episcleral space as the eye is rotated back and forth with forceps

Fig. 8.2a–c. Tactile identification of a rectus muscle border. a The toe of a muscle hook is placed on the conjunctiva near the anticipated location of the rectus muscle border. b While placing mild pressure on the hook in a posterior direction, the hook is advanced toward the muscle. c The hook cannot be advanced and the muscle becomes bunched against the hook when contact is made with the border of the muscle

 

8.1  What to do Prior to Incising the Conjunctival

8.1.3.1 Technique for Rectus Muscle Traction Testing The conjunctiva and episclera are firmly grasped with finetoothed forceps, such as Thorpe forceps, 1–2 mm posterior to the corneal limbus (>Fig. 8.3a). Following the normal physiologic rotational path of the globe, the eye is rotated first horizontally and then vertically (>Fig. 8.3b). These rotations should occur freely, without resistance, in a normal eye. Palpable resistance to passive rotation of the globe, even if mild, can usually be readily detected using this technique. Positive forced ductions indicate the presence of a restrictive problem.

8.1.4 Oblique Muscle/Tendon Forced Traction Testing If surgery is to be performed on the oblique muscle, oblique muscle tracking testing may be indicated prior to surgery to help with surgical planning and during surgery to help assure complete inferior oblique myectomy or superior oblique tenectomy has taken place. Oblique muscle traction testing is only performed under general anesthesia. The technique is most useful prior to surgery on the superior oblique tendon, where results of the test may alter the planned surgical procedure. A patient with a fourth nerve palsy who has a very lax superior oblique tendon may warrant tucking of the tendon rather than a planned inferior oblique weakening procedure, for example. If a decision not to tuck the superior oblique tendon is made, the results of superior oblique tendon traction may help in planning future surgery, if needed. While inferior oblique muscle traction testing is generally less useful than traction testing of other extraocular muscles, the technique has specific important indications. The test can be used to confirm that the entire inferior oblique muscle has been disinserted or transected during surgery. Failure to fully disinsert or transect the inferior oblique muscle during weakening procedures usually fails to produce the desired postoperative result. Unfortunately, the test is not without limitations in this setting and may fail to detect a residual band of intact inferior oblique muscle in some situations [1]. The technique may also be useful in helping to determine if an inferior oblique muscle that has previously undergone myectomy has become reattached to the globe, when considering reoperation on the inferior oblique muscle.

8.1.4.1 Technique for Forced Traction Testing of the Superior Oblique Muscle/Tendon Guyton [2] described a traction test to determine the tightness of both the superior oblique tendon/muscle and the inferior oblique muscle. The technique was later modified by Plager [3] and the procedure described by Plager is reviewed below. A similar technique is used for the Guyton approach. An ad-

Fig. 8.3a,b. Rectus muscle forced traction testing. a The eye is grasped with forceps 1–2 mm posterior to the corneal limbus and is rotated first horizontally and then vertically. b Manual rotation of the globe laterally is incomplete in an eye with a tight medial rectus muscle

vantage of the approach suggested by Guyton is the fact that traction testing can be performed on both the superior and inferior oblique muscles without changing the position of the forceps on the globe. To assess the tautness of the superior oblique tendon, while seated above the patient’s head the globe is firmly grasped at the 4 o’clock and 10 o’clock positions for the right eye (2 o’clock and 8 o’clock positions for the left eye), approximately 1–2 mm posterior to the corneal limbus with fine forceps (>Fig. 8.4a). The next step is critical to oblique muscle traction testing. The surgeon then gently presses the eye into the orbit and simultaneously moves the eye up and in (>Fig. 8.4b). This places the superior oblique tendon under maximum traction. The relative laxity or tautness of the superior oblique tendon can then be palpated. Movement of the globe up and in during this maneuver is limited by a normal and by a tight superior oblique tendon (>Fig. 8.4c), compared with a lax tendon (>Fig. 8.4c). The surgeon can gain additional information by abducting and adducting the eye while simultaneously pressing the globe into the orbit and elevating it (>Fig. 8.5a). As this maneuver is carried out, the superior oblique tendon can be palpated as the globe rolls over the tendon, which has been placed under traction. The profile of the path of deflection of the globe as it is rotated resembles that of a speed bump in a roadway

69

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Techniques of Exposure and Closure

Fig. 8.4a–c. Superior oblique traction testing. a The globe is firmly grasped at the 4 o’clock and 10 o’clock positions for the right eye (2 o’clock and 8 o’clock positions for the left eye). b While gently pressing the globe into the orbit, the surgeon simultaneously elevates and

Chapter 8

adducts the eye, putting the superior oblique tendon under stretch. c Movement of the eye up and in is not limited when the tendon is lax, but is limited by a normal tendon

 

Fig. 8.5a–c. Superior oblique traction testing, continued. a The globe is abducted and adducted while simultaneously pressing the eye into the orbit and elevating it. b The profile of the palpated path deflection

8.1  What to do Prior to Incising the Conjunctival

of the globe created by the tendon resembles that of a speed bump in a roadway. c The deflection produced by the tendon is dependent on the relative tautness of the tendon

(>Fig. 8.5b). The amount of deflection caused by the tendon as the eye rolls over it depends on the relative tautness of the tendon. The possible contour of the palpated deflection path is shown in Fig. 8.5c. The intraoperative appearance of a normal and a lax superior oblique tendon are shown in Fig. 8.6.

8.1.4.2 Technique for Forced Traction Testing of the Inferior Oblique Muscle The procedure is similar to that described for superior oblique traction testing. The globe is firmly grasped at the 2 o’clock and 8 o’clock positions for the right eye (4 o’clock and 10 o’clock positions for the left eye), approximately 1–2 mm posterior to the corneal limbus, with fine forceps. While pressing the globe into the orbit the surgeon simultaneously depresses the globe. Next, the eye is abducted and then adducted. Unlike superior oblique traction testing, traction testing of the inferior oblique muscle is not usually quantified. The muscle is either palpated or not palpated. The path deflection palpated as the eye is rotated and rolls over the inferior oblique muscle resembles that of a speed hump in a roadway (>Fig. 8.7a). The contour of the palpated deflection path is shown in Fig. 8.7b.

8.1.5 Spring Back Test for Slipped or Lost Muscle If a slipped or lost muscle is suspected preoperatively, the spring back test can be helpful prior to starting surgery to help confirm the diagnosis [4]. Upon release, fibro-elastic properties of a rectus muscle cause the globe to recoil back to the mid-

Fig. 8.6a,b. Intraoperative appearance of the superior oblique tendon. a Normal superior oblique tendon, and b a lax superior oblique tendon (b is Courtesy of David A. Plager, MD)

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Techniques of Exposure and Closure

Chapter 8

Fig. 8.7a, b. Inferior oblique muscle traction testing. a The path deflection palpated as the eye is abducted and adducted while simultaneously pressing the globe into the orbit and depressing it resembles that of a speed hump in a roadway. b The contour of the palpated deflection path is shown

line after the globe has been mechanically deflected away from the muscle in an anesthetized patient. This normal recoil does not occur if the muscle is severely slipped or detached from the globe. The globe is grasped with fine forceps 1–2 mm posterior to the corneal limbus and fully displaced away from the suspected slipped or lost muscle (>Fig. 8.8a). The globe is then released while the surgeon observes for recoil of the globe back to or beyond the midline. If the rectus muscle is appropriately attached to the sclera, the eye will recoil or spring back to the primary position (>Fig. 8.8b). If there is a severely slipped or lost muscle, the globe will fail to recoil, but instead will maintain its relative position after release of the forceps (>Fig. 8.8c).

8.2 Conjunctival Incisions for Rectus Muscle Surgery All strabismus surgery requires an incision through the conjunctiva and through Tenon’s fascia. Conjunctival incisions made during strabismus surgery are created to gain access to the episcleral space (sub-Tenon’s space) and all manipulations of the extraocular muscles during routine strabismus surgery occur in this space (Chap. 1). Three surgical techniques to gain access to the episcleral space have been popularized. The two most common conjunctival incisions used for strabismus surgery today are referred to as the limbal conjunctival incision [5] and the fornix [6] (cul-de-sac) conjunctival incision. Fornix incisions are made between adjacent rectus muscles starting approximately 8 mm from the limbus, though their position and orientation may vary significantly depending on surgeon preference and the procedure planned. Limbal incisions involve the creation of a flap incision that is initiated at

Fig. 8.8a–c. The spring back test for a slipped or lost rectus muscle. a The is globe fully displaced away from the suspected slipped or lost muscle with forceps. b The eye will recoil or spring back to the primary position if the muscle is adequately attached to the globe. c The eye fails to return toward the primary position in this eye which has had its medial rectus muscle disinserted, instead maintaining its deflected position

 

the limbus and has its base in the fornix. The advantages and disadvantages of each of these two primary strabismus surgery incision approaches are reviewed. An earlier approach introduced by Swan [7, 8] relied on an incision through the conjunctiva that was concentric with the corneal limbus and located over the rectus muscle to be operated. The Swan incision is reviewed primarily for historical interest, as it has largely been abandoned due its difficulty and higher rate of complications. Other surgical approaches have been proposed, but have never gained wide acceptance. Velez [9], for example, described a radial incision for surgery on the horizontal rectus muscles. Any surgical approach for strabismus surgery must provide adequate surgical exposure, be associated with minimal post­operative adhesion and scar formation, be easy to create and to close, and should facilitate reoperation by limiting the amount of scarring that occurs postoperatively in the episcleral space. The choice of surgical incision is primarily based on surgeon preference, though some situations are best managed with one surgical approach preferentially. For example, while reoperations can usually be easily performed through either a fornix or limbal incision, complex reoperations involving exploration of the posterior aspect of the orbit and involving extensive scarring are often more easily carried out through a limbal incision. Posterior fixation sutures, especially when performed more than 12 mm posterior to the limbus, can often be performed more easily (and perhaps more safely) through a limbal incision, though use of a fornix incision is reasonable in most situations requiring a posterior fixation suture. The inferior oblique muscle is almost always approached surgically through a fornix incision. If the inferior rectus muscle or the lateral rectus muscle is to be operated simultaneously, inferior oblique muscle surgery can be performed through the same limbal incision created to gain access to these rectus muscles. The superior oblique tendon is usually, but not always, operated through a fornix incision. Because identification and isolation of the superior oblique tendon can sometimes be difficult, it is not unreasonable to approach the superior oblique tendon through a limbal incision or to convert a fornix incision to a limbal incision to improve surgical exposure, if necessary.

8.2.1 Fornix (Cul-de-Sac) Incision The fornix conjunctival incision approach to strabismus surgery was popularized by Parks [6] and has undergone modifications by several surgeons. The name is misleading because the incision is not actually made in the fornix, but rather is made on the bulbar conjunctiva, like all conjunctival incisions for strabismus surgery. Fornix incisions have several key advantages compared to limbal incisions. Fornix incisions are easier to construct, require less time than limbal incisions, and they are easier to close at the end of the case. Three muscles can be accessed through a single fornix incision in any quadrant, including the two adjacent rectus muscles and one oblique muscle. The oblique muscles, however, are rarely accessed through an

8.2  Conjunctival Incisions for Rectus Muscle Surgery

inferonasal fornix incision. Fornix incisions are more difficult to use when the conjunctiva is extremely thin, such as in very elderly patients, but can be used for surgery on a patient of any age. We routinely use a fornix incision for strabismus surgery on patients older than 60 years of age. A fornix incision is not a good option for surgery performed under topical anesthesia (Chap. 6), because the manipulation required to perform surgery through a fornix incision is usually not well tolerated by the patient when using the topical anesthesia approach. Patients tend to be more comfortable postoperatively following a fornix incision compared to those who have had surgery through a limbal incision [10] and the cosmetic appearance of the eye is usually superior in the immediate postoperative period. Closure is straightforward and complications related to closure are less likely to occur with fornix incisions compared to limbal incisions (Chap. 19). Additionally, reoperation of a muscle that was initially approached through a fornix incision is typically easier than for one that was initially approached through a limbal incision because there tends to be fewer adhesions between the conjunctiva and episclera anterior to the muscle insertion when a fornix incision has been used. A disadvantage of the fornix approach is the fact that exposure of the surgical site is not as generous as that obtained through a well-constructed limbal incision. This is most likely to be a problem with procedures that require surgical manipulation 12 mm or more posterior to the limbus such as very large recessions, posterior fixation sutures, and reoperations involving the posterior orbit. The option of conjunctival recession is not possible with a standard fornix incision. Additionally, the technique is more difficult to learn in many ways than is the limbal approach, and until the surgeon is experienced in performing surgery through a fornix incision, a relatively skilled assistant is essential.

8.2.1.1 Fornix Incision Technique A fornix conjunctival incision can be made in any of the oblique quadrants between adjacent rectus muscles. In general, incisions placed in the lower quadrants are preferred to those placed in the upper quadrants (>Fig. 8.9). The incision is generally made parallel or nearly parallel to the lid margins, beginning approximately 8 mm posterior to the limbus and extending nasally or temporally as needed. Some surgeons prefer fornix incisions that are more obliquely oriented. This choice is a matter of surgeon preference and has no significant impact on the outcome of surgery or healing. The precise location of a fornix incision depends on a number of factors, including which muscle(s) is to be operated, surgeon preference, the type of surgery (recession versus resection), the size of the recession, the presence of other ocular pathology, and previous surgery. For example, the incision is often placed more posteriorly and closer to the muscle if a large recession is planned, because an incision placed in this manner allows greater exposure of a surgical site that is located further from the corneal limbus.

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8.2.1.1.1 Initial Incision

Fig. 8.9. Potential locations for placement of a fornix incision for rectus muscle surgery. Incisions placed in the lower quadrants are preferred, when possible

Fig. 8.10a–c. Initiation of a fornix incision using one of two approaches. a Placing the adjacent conjunctiva under traction followed by incision, or b direct incision with blunt-tipped scissors without traction

The globe is grasped 1–2 mm posterior to the corneal limbus and positioned for surgery. Curved, locking 0.5-mm forceps are excellent for this maneuver. The conjunctiva is grasped with a fine-tipped forceps, placed under mild anterior traction, and an incision 8–10 mm in size is made (>Fig. 8.10a). Alternatively, blunt-tipped scissors can be placed directly on the conjunctiva and the incision made without grasping the conjunctiva with forceps (>Fig. 8.10b). Moderate pressure needs to be maintained on the scissors during this maneuver. When making a fornix incision medially, the incision should not be continued into the plica semilunaris as this will result in a visible notch in the plica semilunaris postoperatively. Tenon’s fascia is then grasped with forceps and incised to gain access to the episcleral space (>Fig. 8.10c). Some surgeons recommend orienting the incision through Tenon’s capsule at a right angle to the conjunctival incision. This orientation probably offers no significant clinical advantage because traction on the incision during surgery significantly distorts the initial opening, and incision through Tenon’s capsule is more difficult to perform in this manner. It is rarely possible to distinguish a difference in orientation between the conjunctival and Tenon’s capsule incisions at the end of surgery, before closure of the conjunctiva is done. Some surgeons remove a small piece of Tenon’s capsule to facilitate access to the episcleral space.

on the conjunctiva. c Tenon’s fascia is then incised to gain access to the episcleral space

 

8.2.1.1.2 Isolation of a Rectus Muscle A small hook is used to initially isolate the rectus muscle insertion. A Stevens hook is ideal for this purpose. The hook is passed through the incision into the episcleral space. The toe of the hook should initially be placed in contact with the sclera. The hook is then advanced toward the rectus muscle. As the hook makes contact with the muscle, it is rotated so that it becomes parallel with the muscle insertion (>Fig. 8.11a). Placing the toe of the hook initially in contact with the sclera helps

8.2  Conjunctival Incisions for Rectus Muscle Surgery

to assure that the hook is directed under the muscle, rather than in some other, unwanted plane. The small hook is then replaced by a hook that is slightly larger than the width of the muscle insertion (>Fig. 8.11b). A Jamison hook or Green hook is often used for this purpose. To help ensure that the entire width of the muscle insertion has been isolated on the hook, a second large hook is often passed, replacing the existing hook. The assistant surgeon can be very helpful during these steps by retracting the incision with a small hook to ensure that the surgeon has constant access to bare sclera upon which to initiate passage of the muscle hooks.

Fig. 8.11a,b. Isolation of a rectus muscle insertion. a A small hook is used to initially isolate the muscle insertion through the episcleral space. The toe of a hook, initially in contact with the sclera, is rotated parallel to the muscle insertion as the hook is advanced toward the rectus muscle. b The small hook is then replaced by a larger hook to engage the entire muscle insertion

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8.2.1.1.3 Heel or Toe Maneuver Before the conjunctiva is retracted to expose the muscle insertion, the heel or toe maneuver can be carried out to help ensure that the entire muscle insertion has been isolated on the hook (>Fig. 8.12). The toe of the hook is the distal tip of the hook, which often terminates in a bulb or other protrusion. The heel of the hook represents the right angle bend in the distal portion of the hook. After hooking the rectus muscle, the toe of the hook is angled upward, tenting the conjunctiva. An attempt is then made to gently rotate the toe of the muscle hook toward the limbus. If the toe of the muscle hook easily advances to the limbus, the entire muscle insertion has probably been isolated. On other hand, if the toe fails to advance to the limbus, but instead the heel of the hook tends to move posteriorly, the surgeon has failed to isolate the entire muscle insertion and another hook should be passed. Rarely, the surgeon may split the rectus muscle during this maneuver and may be fooled into believing that the entire muscle has been isolated. The pole test, described below, will allow later detection of this problem.

8.2.1.1.4 Exposure of the Muscle Insertion A small hook, such as a Jamison hook, is then is placed between the conjunctiva and the muscle insertion anteriorly. This hook it used to slowly retract the conjunctiva over the muscle insertion while simultaneously rotating the muscle insertion into the incision using the large hook that is under the muscle insertion (>Fig. 8.13a). Once the conjunctiva has been retracted, the intermuscular septum can be seen extending from the toe of the hook toward the globe. The intermuscular septum is grasped with a pair of toothed forceps. A pair of blunt-tipped scissors is used to incise the intramuscular membrane to ex-

Fig. 8.12. The heel or toe test to ensure that the entire muscle insertion has been isolated. The toe of the hook is angled in an anterior direction, tenting the conjunctiva, and then is rotated toward the limbus. On the right: advancement of the toe to the limbus suggests that the

Chapter 8

pose the toe of the muscle hook and underlying bare sclera (>Fig. 8.13b). Tenon’s fascia is lightly grasped 2–3 mm anterior to the muscle insertion and placed under mild traction. It is incised down to bare sclera approximately 1 mm anterior to the muscle insertion (>Fig. 8.13c). Cutting too close to the muscle insertion during this step can result in bleeding from the anterior ciliary vessels and/or damage to the muscle. Some surgeons prefer to omit this step.

8.2.1.1.5 The Pole Test A maneuver referred to by some as the pole test is recommended at this stage of the operation or prior to dissection of Tenon’s capsule anterior to the muscle insertion, as a final step to ensure that the entire rectus muscle insertion has been isolated on the muscle hook (>Fig. 8.14a). The toe of a small hook, such as a Stevens hook, is placed on bare sclera located behind the muscle insertion. While maintaining mild pressure on the globe, the hook is slowly moved around the muscle insertion until it is located anterior to the insertion. If the muscle has been split during attempts to isolate the muscle and thus has not been fully isolated on the large muscle hook, the small hook cannot be advanced anterior to the muscle insertion, instead becoming trapped by the portion of the muscle insertion that has not been isolated (>Fig. 8.14b). When this occurs, the surgeon is obligated to identify and isolate the remainder of the muscle on the hook before proceeding with surgery.

8.2.1.1.6 Dissection of the Muscle Fascia Next, the proximal end of the large muscle hook is directed toward the limbus and the rectus muscle is maintained under mild traction. The intermuscular septum is dissected with

entire muscle insertion has been isolated while (left) failure to advance to the limbus indicates that the entire insertion has not been isolated. The dotted line represents the position of the insertion.

 

8.2  Conjunctival Incisions for Rectus Muscle Surgery

Fig. 8.13a–c. Exposure of a rectus muscle insertion. a A small hook is used to slowly retract the conjunctiva over the muscle insertion while simultaneously rotating the muscle insertion into the incision. b The

intermuscular septum is grasped with a pair of toothed forceps and incised, exposing underlying bare sclera. c Tenon’s fascia is incised down to bare sclera approximately 1 mm anterior to the muscle insertion

sharp dissection to expose the border of the rectus muscle (>Fig. 8.15a). If the surgeon prefers to dissect the epimuscular fascia, it is lightly grasped with forceps, placed under traction, and incised just above the plane of the muscle belly (>Fig. 8.15b). The decision on how extensively to dissect the intramuscular septum and muscle capsule is, to a large extent,

dependent on surgeon preference and the type of surgery to be performed. Some surgeons perform minimal dissection of these structures, while others routinely perform large dissections. Recession, resection, tucking, and other procedures can then be performed on the now isolated rectus muscle as described in later chapters in this textbook.

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Fig. 8.14a,b. The pole test to confirm that the entire muscle insertion has been isolated. a The toe of a small hook is placed on bare sclera located behind the muscle hook. Maintaining contact with the sclera, the hook is slowly moved around the muscle insertion until it is located anterior to the insertion. b The hook cannot be advanced anterior to the muscle insertion if the muscle has been split and a portion of the muscle insertion not yet isolated on the hook, but instead is trapped, unable to be moved anterior to the insertion (left). On the right: note the split in the muscle identified after the full width of the muscle has been isolated on the hook.

Fig. 8.15a,b. Dissection of the rectus muscle fascia. a Sharp dissection of the intermuscular septum is done to expose the muscle border. b Dissection of the epimuscular tissue to expose the muscle belly is done by many surgeons

 

8.2.1.1.7 Closure of a Fornix Incision The decision to perform suture closure of a fornix incision depends on surgeon preference, the state of the patient’s conjunctiva at the end of the case, and the appearance of the incision following surgery. The anterior aspect of the incision is gently pushed posteriorly (>Fig. 8.16a). If the edges of the incision are well approximated by this maneuver, suture closure may be omitted (>Fig. 8.16b). Suture closure is recommended if close approximation of the incision edges does not occur with this maneuver and when the incision is particularly large (>Fig. 8.16c). Suture closure is almost always recommended when a fornix incision has been used to perform surgery on the thin conjunctiva of an elderly patient, because close reapproximation of the wound edges in this setting is uncommon. If suture closure is warranted or desired, one or two simple interrupted sutures at intervals along the incision or a running suture closure may be utilized. Buried knots may be associated with less ocular discomfort postoperatively.

8.2.2 Limbal Incision The limbal approach to strabismus surgery was popularized by von Noorden [5]. Many surgeons prefer limbal incisions because they are universally applicable to any and all rectus muscle operations. The advantages of limbal incisions are many,

8.2  Conjunctival Incisions for Rectus Muscle Surgery

including excellent exposure. Limbal incisions may be especially helpful when performing surgical maneuvers more than 12–13 mm posteriorly to the limbus. The surgeon is usually less dependent on a skilled surgical assistant when using a limbal approach. Reoperations, especially complex reoperations, are thought by many surgeons to be more easily performed through a limbal incision, though a fornix approach can be used by the experienced surgeon for all but the most unusual reoperation procedures. Only one rectus muscle can be operated on through a standard limbal conjunctival incision. The disadvantages of limbal incisions are also numerous. Closure of a limbal incision is more difficult and time consuming than closure of a fornix incision and requires careful attention to detail. If the edges of the conjunctiva are not correctly identified, a number of potential complications can occur, including coiling and retraction of the conjunctival flap and anterior advancement of the plica semilunaris, both of which can be very distressing to patients (Chap. 19). The novice surgeon is often well served to mark the intended position of the limbal incision prior to making it, using a sterile gentian violet skin-marking pen (>Fig. 8.17). This technique not only aids in accurate construction of a limbal incision, but also helps to ensure accurate closure because the dye is usually still visible on the conjunctival edges at the end of surgery, facilitating identification of the corners of the conjunctival flap. This dye is readily washed away during surgery and postoperatively and we have never seen permanent conjunctival pigmentation as a result of its use when used to teach residents the techniques of limbal incision construction.

Fig. 8.16a–c. Closure of a fornix incision. a The anterior portion of the incision is gently pushed posteriorly. b Suture closure is not required when good approximation of the wound edges is present. c Suture closure is recommended when good wound approximation is not achieved

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the corneal limbus, with radial incisions that are 8–10 mm in length into adjacent oblique conjunctival quadrants between adjacent rectus muscles. Placement of limbal incisions for surgery on each of the rectus muscles is shown in Fig. 8.18. Several techniques have been described for the creation of a limbal incision. Any of these techniques is reasonable provided that it results in the construction of a limbal incision that is smooth, has right angle turns connecting the limbal and radial components, and provides adequate exposure of the surgical site. One of the simplest techniques is described below.

8.2.2.1 Limbal Incision Technique Fig. 8.17. A sterile gentian violet skin-marking pen can be used to mark the position of the limbal incision aiding both in the construction of the incision and its closure

The cosmetic appearance of a well-performed and optimally healed limbal incision is generally excellent, and equal to that of a fornix incision. Frequently, however, conjunctival ridges and bumps can be seen on the conjunctival surface even years after surgery. In the immediate postoperative period, eyes that have undergone surgery through a limbal incision tend to be less comfortable than those that have undergone a fornix incision [10]. The limbal approach to strabismus surgery involves creation of a conjunctival flap that is initiated at the limbus and has its base in the fornix. The incision typically involves a region corresponding to 2 to 3 o’clock of the conjunctiva adjacent to

8.2.2.1.1 Initial Incision The surgeon may be seated on the side of the globe opposite the rectus muscle to be operated on, or seated to the right for surgery on the superior rectus muscle. After retracting the globe to expose the conjunctiva over the muscle to be operated, the conjunctiva along the path of one planned radial incision is grasped 2–3 mm posterior to the corneal limbus and incised (>Fig. 8.19a). This should produce an incision that starts at the corneal limbus and extends 4–6 mm posteriorly. One blade of a pair of blunt-tipped scissors is then directed posteriorly and the radial incision extended. The conjunctiva is then elevated and the limbal component of the incision created, often preceded by blunt dissection of the episcleral space near the corneal limbus. A second radial incision is then made at a right angle to the limbus (>Fig. 8.19b). A common mistake that is made when creating the second radial component of the incision involves vertical orientation of the scissors, which produces a conjunctival dog-ear flap (>Fig. 8.19c), rather than an abrupt transition from the limbal to the radial component of the incision, making closure more difficult. Instead, the scissors should be oriented horizontally and flush against the sclera, which produces a sharp, right angle turn.

8.2.2.1.2 Isolation of the Muscle and Dissection of the Muscle Fascia

Fig. 8.18. Position of limbal incisions for surgery on the rectus muscles

The intermuscular septum is opened with blunt dissection on one or both sides of the muscle, adjacent to the muscle border (>Fig. 8.20a). The corner of the conjunctival flap with its underlying adherent anterior Tenon’s capsule is grasped with forceps and placed under mild traction. Blunt-tipped scissors are placed against the sclera and passed posteriorly to further open the episcleral space. The muscle insertion is then isolated on a muscle hook, under direct visualization (>Fig. 8.20b). With the help of a surgical assistant, each corner of the conjunctival flap is grasped with fine forceps and lifted anteriorly, putting the muscle capsule and epimuscular tissue under mild traction. Sharp dissection is then carried out just above the plane of the muscle to dissect the muscle capsule and along

 

8.2  Conjunctival Incisions for Rectus Muscle Surgery

Fig. 8.19a–c. Creating a limbal incision. a An initial radial component of the incision is created, b followed by the limbal and a second radial component of the incision. The scissors should be oriented horizontally and flush against the sclera as the radial portion of the incision is created. c Failing to do so can produce a conjunctival dog-ear flap (arrowhead) instead of the desired sharp, right angle incision (arrow)

the borders of the muscle to incise the intermuscular septum (>Fig. 8.20c). The amount of dissection of these structures depends on the preference of the surgeon and the procedure being performed. Less dissection is usually done for recession procedures than for resection procedures. Some surgeons prefer utilizing a cotton tip applicator or a muscle hook (Chap. 9) to manually disrupt the fine adhesions of the muscle capsule to the muscle belly and the attachments of the intermuscular septum to the borders of the muscle. Recession, resection, tucking, and other procedures can then be performed on the now isolated rectus muscle as described in later chapters in this textbook.

8.2.2.1.3 Closure of a Limbal Incision After completion of surgery on the muscle, careful closure of a limbal conjunctival incision is required and is particularly im-

portant following surgery on the medial rectus muscle where improper closure can have particularly significant adverse functional and cosmetic implications (Chap. 19). The conjunctiva should be unrolled with forceps and the anterior corners of the conjunctival flap identified and grasped with forceps. The surgeon should not assume that the anterior corners of the incision have been identified using this technique alone. The underlying adherent Tenon’s fascia should be lightly grasped with forceps and pulled gently toward the limbus. This maneuver often results in further unfolding of the conjunctival flap, allowing the surgeon to identify the true corners of the flap (>Fig. 8.21a). A suture is then passed through each edge of the conjunctival flap and the edges of the flap sutured to the conjunctiva adjacent to the limbus (>Fig. 8.21b). Buried or exposed knots can be used to close the incision based on surgeon preference, though buried knots may be associated with improved postoperative patient comfort.

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Fig. 8.20a–c. Limbal incision: Isolation of the muscle and dissection of the muscle fascia. a The intermuscular septum is opened with blunt dissection on one or both sides of the muscle. b The muscle insertion is then isolated on a muscle hook, under direct visualization. c The corners of the conjunctival flap are then elevated and sharp dissection of the muscle capsule and intermuscular septum done

8.2.2.1.4 Modified Limbal Incision A modification of the limbal incision that can be used for most simple rectus muscle operations involves creation of a single radical incision (>Fig. 8.22). The left radial incision is generally omitted for a right-handed surgeon and the right radial incision omitted for a left-handed surgeon. Upon completion of surgery, closure requires placement of a single suture.

8.2.2.1.5 Conjunctival Recession Following long-standing strabismus, the conjunctiva can become contracted, producing restrictive forces on the globe that must be reduced or eliminated in order to correct the ocular deviation. One advantage of a limbal incision is that the conjunctiva can be easily recessed when warranted. A simple method of conjunctival recession involves placement of sutures

 

8.2  Conjunctival Incisions for Rectus Muscle Surgery

Fig. 8.21a,b. Closure of a limbal incision. a The true corners of the conjunctival flap (arrowhead) can be best identified by placing traction on the underlying Tenon’s fascia near the edges of the flap. b The conjunctival flap is then sutured back to the limbus with absorbable suture

Fig. 8.22. Modified limbal incision. For most simple rectus muscle operations some surgeons create a two-sided incision, eliminating one of the radial incisions

in the corners of the conjunctival flap and suturing them to the conjunctiva adjacent to the muscle insertion (>Fig. 8.23a). Some surgeons also prefer to place a suture in the middle of the conjunctival flap to secure it to the underlying insertion, though this step is not always necessary unless significant posterior sagging of the flap is present. Recession of the limbal flap is also frequently done to facilitate access to adjustable sutures postoperatively (>Fig. 8.23b).

Indications for conversion may include inadequate exposure of the surgical site, bleeding, and complications that may be best managed with the additional exposure of the surgical site afforded by a limbal incision. Conversion can be easily accomplished with a few simple steps.

8.2.3 Converting a Fornix Incision into a Limbal Incision Occasionally the surgeon finds it necessary to convert a fornix incision into a limbal incision after surgery has begun.

8.2.3.1 Technique The end of the fornix incision nearest the limbus is extended to the limbus (>Fig. 8.24). The incision is then carried along the limbus and a radial incision made in the adjacent conjunctival quadrant (>Fig. 8.24). Closure may require additional sutures along the original fornix incision to reduce the risk of protrusion of Tenon’s capsule through the wound postoperatively.

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Fig. 8.24. A fornix incision may be converted to a limbal incision by extending the fornix incision to the limbus, and then proceeding with the limbal and second radial component of a limbal incision

Fig. 8.23a,b. Conjunctival recession. a The conjunctiva can be easily recessed by suturing the corners of the conjunctival flap to the conjunctiva adjacent to the muscle insertion with or without placement of a suture in the muscle stump. b Recession of a limbal flap can also facilitate access to adjustable sutures postoperatively

This additional suture(s) is often placed prior to converting the fornix incision into a limbal incision.

8.2.4 Swan “Over the Muscle” Incision The Swan incision [7, 8] is described here primarily for historical interest and is rarely used today. Many surgeons feel that the Swan over the muscle technique is more likely to be associated with complications compared to other surgical approaches. Copious bleeding can occur if the conjunctival incision is too deep and enters the muscle. Damage to the muscle itself is more likely to occur during several steps of the procedure, compared with other techniques. Additionally, visible

conjunctival scarring in the palpebral fissure can be cosmetically more objectionable compared with that which occurs with other surgical approaches. Finally, surgical access to the muscle for reoperations is rendered more difficult due to extensive scarring around the muscle.

8.2.4.1 Technique The globe is retracted to expose the conjunctiva over the muscle to be operated. A conjunctival incision is made over the rectus muscle to be operated concentric with the limbus and just anterior to the cul-de-sac (>Fig. 8.25a). For medial rectus muscle surgery, the incision is made 1–2 mm anterior to

 

the plica semilunaris. The incision must be made through the conjunctiva only to avoid extending the incision through Tenon’s capsule and into the muscle, which can result in extensive bleeding and/or damage to the muscle. Next, the conjunctiva is reflected anteriorly to expose Tenon’s fascia anterior to the muscle insertion (>Fig. 8.25b). The intermuscular septum is then identified, grasped with forceps, and incised to expose the underlying sclera (>Fig. 8.25c). A muscle hook is then passed to isolate the rectus muscle. The intermuscular septum on the opposite side of the rectus muscle is then incised (>Fig. 8.25d)

8.2  Conjunctival Incisions for Rectus Muscle Surgery

Fig. 8.25a–e. Swan incision, demonstrated primarily for historical interest. a A conjunctival incision is made over the rectus muscle, and b the conjunctiva is reflected anteriorly to expose Tenon’s fascia anterior to the muscle insertion c The intramuscular septum is incised. d The intermuscular septum on the opposite side of the muscle is then incised exposing the toe of the hook. The muscle is then recessed or resected without separating the muscle from the overlying muscle capsule or the adjacent intermuscular septum.

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made in the oblique conjunctival quadrant adjacent to that aspect of the muscle or tendon to which the surgeon requires access. The incisions are similar in size and placement to fornix incisions made for rectus muscle surgery, though some surgeons prefer to place the incision more posteriorly. If a limbal incision has been used to access the inferior rectus or lateral rectus muscle, the inferior oblique muscle is often approached through the same limbal incision. Because identification and isolation of the superior oblique tendon can sometimes be difficult, some surgeons prefer to approach the superior oblique tendon through a limbal incision. When a limbal approach is desired, an incision is created similar to that which is created for access to the superior rectus muscle.

References 1.

Fig. 8.25a–e. (continued) Swan incision, demonstrated primarily for historical interest. e The conjunctiva is then closed with an interrupted or running suture

allowing the toe of the hook to be visualized. Without further dissection, the muscle is then recessed or resected without separating the muscle from the overlying muscle capsule and intermuscular septum. The conjunctiva is then closed with an interrupted or running suture (>Fig. 8.25e).

8.3 Conjunctival Incisions for Oblique Surgery Surgery on the inferior oblique muscles is almost always performed through a fornix incision, though a limbal incision may be used. A conjunctival incision for oblique muscle surgery is

Coats DK, Paysse EA (1997) Intraoperative traction testing to detect incomplete inferior oblique myotomy/myectomy. J AAPOS 1:197–200 2. Guyton DL (1981) Exaggerated traction test for the oblique muscles. Ophthalmology 88:1035–1040 3. Plager DA (1990) Traction testing in superior oblique palsy. J Pediatr Ophthalmol Strabismus 27:136–140 4. Apers R, De Clippeleir L, Van Lammeren M (1989) Basic principles for strabismus reinterventions. Bull Soc Belge Ophtalmol 232:53–60 5. von Noorden GK (1968) The limbal approach to surgery of the rectus muscles. Arch Ophthalmol 80:94–97 6. Parks MM (1968) Fornix incision for horizontal rectus muscle surgery. Am J Ophthalmol 65:907–915 7. Swan KC (1954) Recession under Tenon’s capsule. AMA Arch Ophthalmol 51:32–41 8. Swan KC (1956) Resection under Tenon’s capsule. AMA Arch Ophthalmol 55:836–840 9. Velez G (1980) Radial incision for surgery of the horizontal rectus muscles. J Pediatr Ophthalmol Strabismus 17:106–107 10. Acuña O, Iturriaga H, Salgado C (2004) Estudio prospective y comparative de cirugía de estrabismo: abordeje limbo versus fórnix. Arch Chil Oftal 61:39–44

Chapter

Recession of the Rectus Muscles and Other Weakening Procedures

9

9 John Taylor is credited with the idea that strabismus could be treated by performing an operation to weaken the extraocular muscles [1]. In the mid eighteenth century he traveled throughout Europe and performed free tenotomies of the extraocular muscles. He often patched one eye and left town before the patch was removed and the results of the surgery became obvious. In 1839, Dieffenbach recorded the first case of an esotropia that was cured with a complete tenotomy of the medial rectus [1, 2]. Following his report, tenotomy of the medial rectus muscles became the standard method of treatment for patients with esotropia. As would now be expected, many patients developed large overcorrections. In an attempt to increase the predictability of strabismus surgery, Jameson introduced the scleral suture technique in 1922 [3]. He noted that direct suturing of the muscle to the sclera allowed the surgeon to more accurately grade the weakening effect as well as provided the surgeon with knowledge about the new attachment site on the globe. Modern-day conventional recessions are based upon Jameson’s original concept. Although the needles and sutures used for strabismus surgery have achieved significant advances since Jameson’s time, the basic recession technique used today remains remarkably similar. This chapter will review rectus muscle recession techniques including standard recessions, hang-back recessions, and other techniques designed to reduce the effect of rectus muscle contraction on the globe. In addition to general instructions about recession techniques, specific guidelines and suggestions for each of the four rectus muscles will also be addressed.

9.1 General Principles for Recession of the Rectus Muscles By moving a rectus muscle posterior to its original insertion site and reattaching it to the sclera, the length/tension curve of the muscle is changed. This has the effect of “weakening” the muscle’s effect on the globe. For most recessions, this effect is seen clinically only as a change in the alignment of the eye. Ductions do not appear to be limited unless a very large recession is performed, typically involving placement of the muscle posterior to the equator. This weakening effect probably occurs because of both a reduction in the distance between the origin and new insertion of the muscle, and changes in the relationship between Tenon’s capsule, the intermuscular septum, and

the rectus muscle pulleys. The relationship between the amount of recession required and the size of the deviation treated is not linear. As can be seen in Table 9.1, the recession effect obtained from retroplacing the medial rectus is initially linear, but as the size of the recession increases, the relative effect of the procedure increases. Once the muscle is placed behind the equator, the incremental effect of further recession is reduced. The “safe” limit for a recession depends on the condition being treated. In the mid twentieth century, it was believed that the medial rectus muscle could not be recessed more than 5.0 mm without significantly interfering with movement of the eye. This belief resulted in many cases of congenital esotropia being undertreated. In an effort to improve the success rate of surgery, often three or four muscles were operated at one time. It was later recognized that recessions of at least 7 mm could be performed without producing an adduction deficit. This led to a higher success rate of surgery, particularly for larger deviations, while avoiding the need to operate on a third or fourth muscle. Some studies have shown that even larger recessions can be performed on the medial rectus muscle without creating a duction deficit [4]. In some situations, a rectus muscle may be recessed considerably further. With the use of the hang-back recession technique, large recessions can be performed easily and safely. The intentional creation of a duction limitation may be required for effective treatment of some conditions. For example, a patient with a large exotropia in a poorly seeing eye will usually gladly tolerate the requisite abduction deficit that will occur after a large recess and resect operation in order to avoid the need to operate on the sound eye. Therefore, we do not subscribe to the notion of a “maximum” rectus muscle recession. Table 9.1. Typical size of bilateral medial rectus recession for esotropia Deviation (PD)

Recession from the original insertion (mm)

15

3

25

4

35

5

50

6

70

7

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9.2 Measurement of Recession 9.2.1 Muscle Insertion Artifacts The distance a muscle is moved during a recession procedure can be measured from either its original insertion site or its distance from the limbus. There are a number of reports in the literature demonstrating variability of rectus muscle insertion sites as referenced to the limbus [5, 6]. This is especially true of the medial rectus muscle insertion. The relationship between the muscle insertion site and the limbus has been shown to be particularly variable in young patients before the anterior segment is fully developed. Sevel [7] examined the insertions of the extraocular muscles and discovered that posterior movement of the muscle tendon from the limbus along with growth of the anterior segment of the eye cause the rectus muscle insertions to reach their approximate adult location sometime between the ages of 18 months and 2 years. This fact has also been demonstrated clinically. Barsoum-Homsy [8] measured the distance between the medial rectus muscle insertion site and the limbus in children under 1 year of age undergoing surgery for congenital esotropia. Among the 52 eyes examined, the insertion site varied between 3.0 and 5.5 mm posterior to the limbus. In addition to the variability of rectus muscle insertion distances from the limbus, other authors have reported potential intraoperative changes in the apparent insertion site, which can affect the recession measurement. Keech and coworkers [9] found that disinsertion of the medial rectus muscle resulted in a mean reduction in the distance between the muscle insertion site and the limbus of 0.9 mm. In addition to this change, the use of fixation forceps on the insertion, to abduct the eye, resulted in an advancement of the medial rectus muscle insertion an additional 0.3 mm toward the limbus. Kushner and co-workers [10] demonstrated a similar anterior displacement of rectus muscle insertion sites of approximately 1 mm when the globe was fixated by placing forceps on the rectus muscle stump after detachment of the muscle from the sclera. Because of the potential for the insertion site to vary between individuals and for the insertion site to change during the course of surgery, some surgeons are concerned that measuring the amount of recession from the original muscle insertion site may alter the amount of recession actually achieved from a given surgery. Surgeons with this belief recommend measuring the desired amount of retroplacement of the muscle from the limbus, because the limbus represents a stable landmark from which to base this important surgical measurement [11]. The axial length of the globe has also been reported to play an important role in the size of a rectus muscle recession required for a given deviation [12]. Some surgeons alter their surgical plan based upon the axial length of the eye [12, 13]. The distance the muscle is moved along the globe can be measured using a cord length or arc measurement. Clark and Rosenbaum [14] performed a geometric analysis to determine the measurement difference between true arc length measurements compared with ruler and caliper measurements based upon the size of the recession being performed and the axial

Chapter 9

length of the eye. They found that both a curved ruler and caliper were accurate when measuring arc lengths of 9.0 mm or less. For longer arc length measurements, accuracy was found to be dependent upon the axial length. For recessions greater than 9.0 mm in magnitude, a curved ruler was more accurate than calipers when the axial length of the eye was typical for the average patient population (21–24 mm). However, for smaller and larger eyes, a curved ruler can introduce clinically important measurement errors for arc length measurements as small as 12 mm in small eyes and 14 mm in large eyes. We generally use a caliper for our measurements. For larger recessions where the use of a caliper can be cumbersome, the measurements can be made in two steps. The amount of recession to be performed is divided in half. The caliper is then used to mark the sclera for one-half the recession distance. This mark is then used to perform a second measurement of equal magnitude to mark the final position for suture placement.

9.3 Specific Considerations for Surgery on Individual Rectus Muscles Unique considerations for performing surgery on each of the rectus muscles will be reviewed, followed by a review of rectus muscle recession techniques.

9.3.1 Medial Rectus Muscle Unlike the other rectus muscles, the medial rectus muscle does not have any direct attachments to an adjacent oblique muscle. Because of this, the medial rectus muscle is more difficult to retrieve should it be lost at the time of surgery. Excessive dissection of the intermuscular membrane and muscle capsule is discouraged, in part for this reason. In addition to being unnecessary, it may alter the muscle pulleys and increase the risk of inadvertent muscle damage during surgery [15].

9.3.2 Inferior Rectus Muscle The inferior rectus muscle has fascial attachments to Lockwood’s ligament, the inferior orbital septum, and the tarsus of the lower eyelid. Because of these attachments, recession of the inferior rectus may produce retraction of the lower eyelid (Chap. 26). Lid retraction may be seen with even moderate inferior rectus muscle recessions. Therefore, techniques designed to minimize the risk of lid retraction when performing a recession on an inferior rectus muscle are recommended, especially when large recessions are performed. Briefly described here, these techniques are reviewed in detail in Chap. 26. Meyer and co-workers [16] described the use of primary infratarsal lower eyelid retractor lysis to prevent eyelid retraction after inferior rectus muscle recession [16]. This technique prevented lower eyelid retraction even with recessions of up to 10 mm. Advancement of the capsulopalpebral head after recession of

 

the inferior rectus muscle has also been shown to minimize lower eyelid retraction [17]. Finally, generous dissection of the attachments between the inferior rectus and the lower eyelid can reduce lower eyelid retraction (>Fig. 9.1). Dissection is required to at least 12 mm posterior to the insertion of the inferior rectus. It is important to visualize the adjacent vortex veins during this dissection to avoid injuring them, a complication that can cause significant bleeding.

9.3.3 Lateral Rectus Muscle The insertion site of the inferior oblique muscle lies posterior to that of the lateral rectus muscle insertion. Therefore, the strabismus surgeon should exercise caution when attempting to isolate the lateral rectus muscle insertion on a muscle hook to avoid inadvertently incorporating the inferior oblique muscle on the muscle hook. This risk can be minimized by either passing the muscle from the superior aspect of the lateral rectus muscle insertion or by avoiding the tendency to pass the hook too deeply into the orbit during attempts to hook the lateral rectus muscle. During reoperation procedures on a previously

9.4  Rectus Muscle Recession Techniques

recessed lateral rectus muscle, this may be more difficult. Direct visualization of both the lateral rectus and the inferior oblique muscles is helpful. If the insertion of the inferior oblique muscle is mistakenly moved during surgery on the lateral rectus muscle, unexpected motility disturbances may occur (Chap. 25).

9.3.4 Superior Rectus Muscle The superior oblique tendon passes inferior to the superior rectus muscle starting approximately 5 mm posterior to the nasal border of the superior rectus muscle insertion. It is important to avoid inadvertently hooking the superior oblique tendon when the superior rectus muscle is initially hooked. If the superior oblique tendon is unknowingly hooked along with the superior rectus muscle insertion, it is possible to perform an unintentional tenotomy on the superior oblique tendon when the superior rectus muscle is detached from the globe, potentially producing a significant iatrogenic motility disturbance. Once the insertion of the superior rectus muscle is isolated on a muscle hook, it should be inspected to ensure that the superior oblique tendon has not been inadvertently hooked. If this has occurred, the superior oblique tendon can be gently lifted off the surface of the globe while a new muscle hook is placed under the superior rectus muscle insertion, excluding the superior oblique tendon (>Fig. 9.2). The superior oblique tendon can also be retracted posteriorly, away from the superior rectus muscle insertion, while a new hook is placed. Similar to the relationship between the inferior rectus muscle and the lower eyelid retractors, the superior rectus muscle has significant attachments to the levator muscle of the upper eyelid through the fascial sheaths of these two muscles. Moderate to large recessions of the superior rectus may produce upper eyelid retraction. Dissecting these attachments at least 12 mm posterior to the insertion site of the muscle at the time of superior rectus muscle recession will help to minimize this postoperative complication (Chap. 26).

9.4 Rectus Muscle Recession Techniques

Fig. 9.1. Recession of the inferior rectus muscle demonstrating the appearance of the muscle after generous dissection of the attachments between the inferior rectus muscle and the lower eyelid retractors to minimize lower eyelid retraction following inferior rectus recession

The general technique for rectus muscle recession is similar for each of the four rectus muscles. Specific concerns regarding each individual rectus muscle are reviewed above. Each of the rectus muscles may be exposed using either a limbal or a fornix incision. In most situations, the choice of surgical approach depends entirely on the preference of the surgeon. There are a few isolated situations in which one surgical approach may be preferred over the other as reviewed in Chap. 8. For most cases, we prefer a fornix incision. Reoperations and surgery on patients with a thin or friable conjunctiva are are often preferentially operated through a limbal incision, a technique that requires minimal stretching of the conjunctiva, reducing the risk of its tearing, a complication which may make subsequent closure more difficult. The detailed techniques of conjunctival incisions, rectus muscle isolation, and of conjunctival closure are reviewed in Chap. 8, and will not be repeated here.

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Fig. 9.2a,b. Isolation of the superior rectus. a The tendon of the superior oblique has been unintentionally isolated in the hook along with the superior rectus muscle. b The superior rectus muscle and superior

9.4.1 Standard Rectus Muscle Recession Technique 9.4.1.1 Placing Suture Near the Muscle Insertion After the rectus muscle is isolated on a muscle hook, a suture is placed in the muscle near its insertion into the sclera. The suture should generally be placed no closer than 1 mm from the muscle’s insertion into the sclera. We prefer the use of a single double-armed polyglactin suture. A suture pass is started at the midpoint of the muscle and placed half thickness through the muscle. This is referred to as the transverse pass. The needle is allowed to exit at the border of the muscle (>Fig. 9.3a). When passing the needle away from the surgeon, it is sometimes difficult to visualize the exit location of the needle from the muscle. If the needle stays in place once its tip has exited the muscle, it is in proper location. However, if the needle appears unstable, it has most likely been passed full thickness through the muscle (>Fig. 9.3b). In this case, the suture should be partially withdrawn and passed again. The suture is then passed in the opposite direction starting in the center of the muscle, so that the transverse pass crosses the entire width of the muscle posterior to its insertion site. The small distance between the sclera and the suture adds a negligible resection effect following surgery. Following completion of the transverse pass, locking suture passes are made at the borders of the muscle near the insertion.

Chapter 9

oblique tendon are lifted off the surface of the globe to allow passage of a second muscle hook to isolate the insertion of the superior rectus muscle only

These border locking suture passes should incorporate at least 1mm of muscle to achieve a secure muscle-suture union (Unpublished data). The needle is passed full thickness through the muscle from the posterior to the anterior aspect of the muscle and behind the transverse suture pass (>Fig. 9.4a). The needle should not be passed through the anterior ciliary vessels, as this may result in significant bleeding. It is sometimes helpful to pass the needle around these vessels in order to ligate them and prevent bleeding when the muscle is later detached from the globe. Care should be taken to pass the needle directly through the muscle. After the suture is passed full thickness through the muscle, the needle holder is passed through the suture loop, grasping the needle and pulling it through the suture loop to create a locking bite (>Fig. 9.4b). It is preferable to grasp the suture rather than the needle during this step to prevent damage to the needle.

9.4.1.2 Detachment of the Muscle from the Globe The muscle sutures are placed between the index finger and thumb of the hand holding the muscle hook. Independent control of the sutures is helpful. If the surgeon grasps the muscle hook in his or her hand and is able to pull the sutures with his or her fingers independently of the hook, more space can be created between the insertion site of the muscle and the sutures, facilitating detachment of the muscle and reducing the risk of cutting the muscle sutures (>Fig. 9.5).

 

Fig. 9.3a,b. Transverse needle pass near the muscle insertion. a The needle is placed into the muscle near the midpoint of the muscle width near the insertion site. It is passed half thickness through the muscle

9.4  Rectus Muscle Recession Techniques

until the needle tip exits the border of the muscle. b Note that the tip of the needle tends to fall toward the globe if the needle has been unintentionally passed full thickness through the muscle

Fig. 9.4a,b. Locking suture pass. a The suture is passed full thickness through the muscle posterior to the transverse pass and around nearby anterior ciliary vessels. The locking bite should be at least 1 mm in width. b Completion of the locking bite

91

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Chapter 9

placed. This measurement can be made from the limbus or the original insertion site of the muscle as described previously (>Fig. 9.6a, b). The mark on the sclera is made by indenting the sclera at the desired recession site using a caliper. This maneuver displaces fluid from the sclera and allows visualization of the underlying choroid, creating the appearance of a blue spot on the sclera. The surgeon should be careful not to press too firmly with the caliper at either the anterior or the posterior site of the caliper placement. Inexperienced surgeons often neglect to carefully observe the anterior tip of the caliper while pressing on the sclera with the posterior caliper tip. They may unknowingly place too much pressure on the anterior tip of the caliper and perforate the globe during this step. The sclera may be marked for both needle passes at this point, if desired. However, the second mark often disappears by the time the surgeon is ready to pass the second needle. The caliper tips can be covered with ink from a sterile gentian violet skin-marking pen to create a sustained mark on the sclera, if desired. The needle is then placed into the sclera at the previously marked positions. The needle pass in the sclera should be a minimum of 2 mm in length and 200 µm in depth [11]. Many surgeons prefer much longer scleral bites, but these minimum values are sufficient to secure the muscle to the sclera. The first needle exits the sclera and is allowed to remain in place. The second needle is then passed in a similar fashion. This “crossed swords” technique allows the sutures to be passed in close proximity to each other without the second needle pass damaging the previously passed suture (>Fig. 9.7). It is not necessary however, for the two needles to exit the sclera in close proximity. The sutures are then pulled through the sclera in the direction of their pass in order to avoid cheese wiring of the sclera. The sutures are then tied and cut making certain that the muscle remains in place at its new insertion site by maintaining anterior traction on the sutures while they are being tied (>Fig. 9.8). If the needle passes are made too close to each other, the central portion of the muscle may sag posteriorly. This can be corrected by passing the needle back through the midportion of the muscle and behind the original suture, prior to cutting the muscle sutures. The suture is then tied to bring the central portion of the muscle up to its intended attachment site (>Fig. 9.9).

Fig. 9.5. Independent control of the muscle hook and the sutures while detaching the muscle from the sclera. Note that the surgeon is able to independently lift the sutures and provide more space to safely cut the muscle from its insertion site

9.4.1.3 Securing the Muscle to the Sclera at its New Location Locking forceps are placed on the edges of the muscle stump after the muscle has been detached from the sclera. The sclera is marked to identify the entrance site for the upcoming needle pass where the new insertion site of the muscle will be

9.4.2 Hang-Back Recession Techniques 9.4.2.1 Introduction In an attempt to improve outcomes associated with conventional extraocular muscle surgery, Jampolsky popularized the concept of the adjustable suture in the 1970s [18]. Use of adjustable sutures led to the development of hang-back or suspension recession procedures. Repka and Guyton [19] performed strabismus surgery using techniques that are key to the adjustable suture technique, but without attempting to perform a postoperative adjustment. This procedure became known as a hang-back recession. The procedure described by

 

9.4  Rectus Muscle Recession Techniques

Fig. 9.6a,b. Marking the sclera for the rectus muscle recession. a Measurement from the limbus, or b measurement from the original insertion site

Fig. 9.7. Passage of the needles in the sclera using the “crossed swords” technique

Fig. 9.8. The muscle has been pulled up to its new insertion and the sutures have been tied and cut

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Fig. 9.9a–c. Correcting malposition of the new muscle insertion. a The scleral sutures have been placed too close together, causing the central aspect of the muscle to sag posteriorly. This can be corrected by

Guyton and Repka [19] differed from earlier “loop” recessions, a term first coined and popularized by Gobin in the 1960s [20]. Gobin’s recession used two separate sutures that were placed at the edges of the muscle and the needles were widely separated [20]. This separation of the sutures makes measurement of the size of a recession more difficult. Both experienced and occasional strabismus surgeons may effectively use hang-back and hemi hang-back techniques. The hang-back procedure can be used with recession of any of the rectus muscles. The muscle can be approached using either a limbal or fornix incision. The techniques have several potential advantages. The procedure is conducted at the original insertion site (hang-back) or more anterior then a conventional recession (hemi hang-back). Because of this, exposure is excellent regardless of the amount of recession being performed. This makes the surgeon much less dependent on the skills of a surgical assistant, especially for large recessions. Improved exposure and the more anterior location of the area to be manipulated during surgery may result in less tendency for deep needle passes, minimizing scleral and eye wall perforations, which may be more likely to occur with more posterior needle passes in areas where exposure is less optimal. This may be especially true for less experienced strabismus surgeons. In the event that a perforation does occur when using a hang-back approach, it is unlikely to result in damage to the retina because the rectus muscle insertions, with the exception of the superior rectus muscle insertion, are located anterior to the ora serrata. Some strabismus surgeons have raised concerns about the use hang-back techniques. The most commonly raised concerns have been the issue of possible forward migration of the muscle before it has firmly reattached to the sclera. If this did indeed occur with any appreciable frequency, the number of undercorrections using this technique would be expected to be larger than with the conventional approach. Clinical studies, however, have not found this to be the case [21, 22]. Additionally, surgeons who perform adjustable suture surgery rarely express this same concern, even though the muscle is not directly secured to the sclera during adjustable procedures either.

Chapter 9

b passing the needle through the central portion of the muscle, behind the original suture line, and c tying the suture to bring the center of the muscle forward

9.4.2.2 Securing the Muscle to the Sclera The muscle is isolated and disinserted as previously described in Chap. 8 and toothed locking forceps are placed on the borders of the original insertion site. The suture needles are passed through the original insertion site in crossed swords fashion. The needles are passed at an angle that allows both to emerge anterior to the insertion and as close together as possible (>Fig. 9.10). If the distance between the needle exit sites is too large, measurement inaccuracies are more likely when recessing the muscle. If the needle exit sites are a large distance apart, an adjustment of the measurement made along the sutures in the next step can be added to compensate for the problem; in most cases an increase of 0.5 mm will be sufficient.

9.4.2.3 Measuring the Recession The sutures are advanced anteriorly through the sclera until the muscle rests firmly against the posterior aspect of the insertion. Unexpected, additional recession will occur if the muscle is not brought fully anteriorly in this step. This is especially likely to occur when the muscle is tight and has an increased tendency to retract away from the insertion site during this step of the procedure. Calipers are placed perpendicular to the globe at the insertion site and a locking needle holder placed across the sutures as directed by the caliper measurements (>Fig. 9.11). During this step, the caliper should rest gently on the insertion site. A smaller than intended recession will result if the caliper is pressed too firmly into the sclera during this step. To avoid errors during this step, we recommend that the surgeon hold the caliper against the globe and simultaneously place anterior traction on the muscle sutures to place the muscle in apposition with the original insertion site while the surgical assistant places the needle holder across sutures, as directed by the surgeon.

 

Fig. 9.10. Scleral needle passes during the hang-back recession technique. The needles are passed through the original insertion site to emerge side-by-side in a crossed swords pattern

9.4  Rectus Muscle Recession Techniques

Fig. 9.11. Marking the suture for hang-back recession. The muscle is pulled firmly forward against the original insertion site and the caliper is placed along the suture arms. A locking needle holder is placed across the sutures inside the proximal caliper tip

The suture is then tied and trimmed with the needle holder in place. The needle holder is removed and the globe is rotated away from the muscle, which causes the muscle to retract posteriorly. Alternatively, the muscle can also be placed into its new position by gently pulling the suture through the suture tract with a needle holder until the suture knots restrict further movement. If desired, the final position of the muscle can be confirmed by caliper measurement (>Fig. 9.12).

In some animal experiments, very large rectus muscle recessions performed with the hang-back technique have been demonstrated to migrate anteriorly following the procedure. If this were to occur following hang-back surgery in patients, an undercorrection would result. To mitigate this potential prob-

Fig. 9.12. Completing the hang-back recession. The sutures are cut and tied against the needle holder. The muscle is moved to its new posterior position by gently pulling on the sutures. The accuracy of the recession can verified with a caliper, if desired

Fig. 9.13. Large recession using a hemi hang-back technique. The needles are passed halfway between the original insertion site and the desired new insertion position. The muscle is then further recessed using a standard hang-back technique

9.4.2.4 Hemi Hang-Back Modifications

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lem, some surgeons prefer to use the hemi hang-back recession technique for recessions larger than 8 mm. In this method, the suture needles are passed through the sclera approximately half the distance between the original insertion site and the desired new recession position. As with the hang-back procedure, it is important that the needles exit close to one another in a crossswords configuration. The muscle is then brought up to this midpoint and the remainder of the procedure is identical to the standard hang-back method (>Fig. 9.13).

9.5 Modified Recession Procedures Most recession procedures are performed using one of the techniques described above. Occasionally, modifications are required to address A- and V-patterns, scleral abnormalities, explants, and other anatomical variations. A few of the most common modifications and indications are reviewed below.

9.5.1 A- and V-Patterns Vertical transposition of the horizontal rectus muscles is an effective method for treating small to moderate A- and V-pattern horizontal strabismus [23]. This technique is commonly utilized to treat A- and V-patterns when oblique muscle dysfunction is not present. Offsetting the horizontal rectus muscle insertion up or down during recession or resection surgery weakens the action of that muscle when the globe is moved in the direction of the offset. For example, if the medial rectus muscles are up shifted one-half tendon width, their horizontal action is diminished in up gaze. It follows that moving the medial rectus toward the apex of an A- and V-pattern is appropriate for correcting the incomitant deviation. Conversely, moving the lateral rectus muscle toward the open end of the A- or V-pattern is also appropriate for correcting the incomitant deviation (>Fig. 9.14). This is true regardless of whether a recession or resection procedure is performed. It is generally accepted that offsetting up or down one-half tendon width of two horizontal rectus muscles, irrespective of whether it is performed on the medial rectus or the lateral rectus muscle, or whether it is com-

Fig. 9.14. Treatment of A- and V-pattern strabismus. The medial rectus muscles are shifted toward the “apex” of the pattern. The lateral rectus muscles are shifted toward the “open” end of the pattern

Chapter 9

bined with a recession or resection of the muscles, will correct approximately 15 prism diopters of an A- or V-pattern. The amount of pattern correction is proportional to the amount of preoperative pattern that was present [24, 25]. Vertical offsets of the horizontal rectus muscles may be performed symmetrically and bilaterally, or may be confined to one eye.

9.5.2 Recession Following Scleral Buckling Procedures Strabismus surgery on patients who have undergone previous scleral buckling procedures can be complex. Both the ability to isolate a rectus muscle and the process of recession itself are rendered more difficult by the presence of an encircling element and other explants, as well as associated scarring that occurs as a result of retinal surgery. Modifications of surgical techniques that may be helpful in these situations are reviewed in Chap. 27.

9.5.3 Recessions in Patients with Thin Sclera In some patients, the sclera can be exceedingly thin and the risk of perforation substantially increased. Coats and Paysse [26] described a procedure to eliminate the risk of scleral perforation in susceptible patients. Their technique avoids placement of sutures directly into the sclera and is reviewed in Chap. 27.

9.5.4 Free Tenotomy of a Rectus Muscle Occasionally the need arises to perform a free tenotomy of a rectus muscle without reattaching it to the sclera, a procedure that is not unlike that described by Dieffenbach in 1839 [1]. Indications may include complete third nerve palsy, congenital fibrosis syndrome and other strabismus disorders where there is a need to maximally weaken a rectus muscle. Merely cutting the muscle free from its attachment to the globe is often unpredictable. The muscle may reattach to the globe and continue to exact some force on the globe. This may be especially true when the lateral rectus muscle is disinserted in order to treat the exotropia associated with a third nerve palsy. To reduce this residual effect, the muscle should be allowed to retract through Tenon’s capsule and the opening within the capsule closed with sutures. Simultaneous resection of a portion of the distal aspect of the muscle will reduce the tendency for forward migration of the muscle and reattachment to the globe. Obviously, the surgeon should be relatively certain that later reversal of the procedure will not be required. If there is a possibility that the disinsertion procedure might later need to be reversed or modified, a nonabsorbable suture can be placed through the muscle and secured to the inner surface of Tenon’s capsule.

 

9.5.5 Recession with Fixation to the Adjacent Orbital Wall An alternative procedure for use when maximum weakening of a rectus muscle is desired is to both recess the rectus muscle and to suture it to the periosteum of the adjacent orbital wall using nonabsorbable suture. This procedure, most often indicated for use on the lateral rectus muscle, is described in Chap. 15.

9.5.6 Y Splitting of the Lateral Rectus An upshoot or downshoot may be seen in some cases of Duane syndrome. Upshoots and downshoots may occur secondary to a tight lateral rectus muscle „slipping“ over the surface of the globe during adduction. This has been characterized as the „leash phenomenon.“ Co-innervation of a horizontal and vertical rectus muscle has also been suggested as a cause of upshoots and downshoots, though this has not been demonstrated electromyographically. Upshoots and downshoots can be corrected by splitting the anterior aspect of the lateral rectus muscle into a „Y“ formation. The two ends of the muscle are then sutured to the globe approximately 10 mm apart from each other, reducing the tendency of the muscle to side slip along the globe during adduction. A small concurrent recession is required to prevent development of exotropia in the primary.

References 1. 2. 3. 4.

5.

6.

7.

Berg F (1967) The Chevalier Taylor and his strabismus operation. Br J Ophthalmol 51:667–673 Dieffenbach J (1839) An die schielen und die heilung. Berlin Med Zeitung 46:27 Jameson P (1922) Correction of squint by muscle recession with scleral suturing. Arch Ophthalmol 51:421–432 Damanakis AG, Arvanitis PG, Ladas ID, Theodossiadis GP (1994) 8 mm bimedial rectus recession in infantile esotropia of 80-90 prism dioptres. Br J Ophthalmol 78:842–844 de Gottrau P, Gajisin S, Roth A (1994) Ocular rectus muscle insertions revisited: an unusual anatomic approach. Acta Anat (Basel) 151:268–272 Souza-Dias C, Prieto-Diaz J, Uesugui CF (1986) Topographical aspects of the insertions of the extraocular muscles. J Pediatr Ophthalmol Strabismus 23:183–189 Sevel D (1986) The origins and insertions of the extraocular muscles: development, histologic features, and clinical significance. Trans Am Ophthalmol Soc 84:488–526

References 8. 9. 10.

11. 12.

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18. 19.

20. 21.

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25.

26.

Barsoum-Homsy M (1981) Medial rectus insertion site in congenital esotropia. Can J Ophthalmol 16:181–186 Keech RV, Scott WE, Baker JD (1990) The medial rectus muscle insertion site in infantile esotropia. Am J Ophthalmol 109:79–84 Kushner BJ, Preslan MW, Vrabec M (1987) Artifacts of measuring during strabismus surgery. J Pediatr Ophthalmol Strabismus 24:159–164 Helveston E (1993) Surgical management of strabismus. An atlas of strabismus surgery, 4th edn. Mosby, St. Louis, Mo. Kushner BJ, Lucchese NJ, Morton GV (1989) The influence of axial length on the response to strabismus surgery. Arch Ophthalmol 107:1616–1618 Kushner BJ, Qui CO, Lucchese NJ, Fisher MR (1996) Axial length estimation in strabismic patients. J Pediatr Ophthalmol Strabismus 33:257–261 Clark RA, Rosenbaum AL (1999) Instrument-induced measurement errors during strabismus surgery. J AAPOS 3:18–25 Clark RA, Demer JL (2006) Magnetic resonance imaging of the effects of horizontal rectus extraocular muscle surgery on pulley and globe positions and stability. Invest Ophthalmol Vis Sci 47:188–194 Meyer DR, Simon JW, Kansora M (1996) Primary infratarsal lower eyelid retractor lysis to prevent eyelid retraction after inferior rectus muscle recession. Am J Ophthalmol 122:331–339 Kushner BJ (1992) A surgical procedure to minimize lower-eyelid retraction with inferior rectus recession. Arch Ophthalmol 110:1011–1014 Jampolsky A (1979) Current techniques of adjustable strabismus surgery. Am J Ophthalmol 88:406–418 Repka MX, Guyton DL (1988) Comparison of hang-back medial rectus recession with conventional recession. Ophthalmology 95:782–787 Gobin MH (1968) Recession of the medial rectus muscle with a loop. Ophthalmologica 156:25–27 Breckenridge AL, Dickman DM, Nelson LB, Attia M, Ceyhan D (2003) Long-term results of hang-back medial rectus recession. J Pediatr Ophthalmol Strabismus 40:81–84 Rodrigues AC, Nelson LB (2005) Long-term results of hemihang-back lateral rectus recession. J Pediatr Ophthalmol Strabismus 42:296–299 Knapp P (1959) Vertically incomitant horizontal strabismus: the so-called “A” and “V” syndromes. Trans Am Ophthalmol Soc 57:666–699 Scott WE, Drummond GT, Keech RV (1989) Vertical offsets of horizontal recti muscles in the management of A and V pattern strabismus. Aust N Z J Ophthalmol 17:281–288 Ribeiro GD, Brooks SE, Archer SM, Del Monte MA (1995) Vertical shift of the medial rectus muscles in the treatment of A-pattern esotropia: analysis of outcome. J Pediatr Ophthalmol Strabismus 32:167–171 Coats DK, Paysee EA (1998) Rectus muscle recession and resection without scleral sutures. J AAPOS 2:230–233

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Resection of the Rectus Muscles and other “Strengthening” Procedures

10

Though rectus muscle resection is commonly referred to as a strengthening procedure, this characterization is technically inaccurate. In reality, resection surgery alters the relationship of the rectus muscle to the globe, changing its length–tension curve. Like the clinical effect of recession, the “strengthening” of a muscle is generally seen only in the change that occurs in the alignment of the eye(s) upon which the resection is performed. A significant change in the movement of the eye is not clinically obvious following standard rectus muscle resection surgery. Compared to rectus muscle recession, a resection procedure generally produces greater postoperative discomfort and conjunctival injection. Additionally, the muscle that is sutured to the original insertion site after the resection has taken place is thicker than the tendon, and may become visible beneath the conjunctiva postoperatively. This is especially true for the medial rectus muscle, a finding that can be cosmetically distressing to some patients. Dellen formation is more likely to occur due to greater edema of the conjunctiva adjacent to the limbus following resection surgery (Chap. 19). Large resections of the medial rectus muscle may result in mild to moderate anterior displacement of the plica semilunaris, which can be a cosmetic concern. For these reasons and others, many surgeons prefer to perform recession procedures when possible. Despite these drawbacks, rectus muscle resection procedures are effective and they do play an important role in the treatment of strabismus. Common indications in which a resection may be preferred include the desire to limit surgery to only one eye and treatment of a consecutive or recurrent deviation in a patient who has previously undergoing recession surgery. This chapter will review several commonly used rectus muscle resection techniques. Additionally, rectus muscle tucking procedure will be reviewed.

10.1 Technique of Rectus Muscle Resection The approach to resection of the rectus muscles is similar in many ways to the techniques used for rectus muscle recession surgery. The techniques for exposure and isolation of the muscle and closure of the conjunctiva are reviewed in detail in Chap. 8 and will not be reviewed here. Many surgeons perform additional steps during resection procedures to produce added

10 security when reattaching the muscle to the globe to reduce the risk of developing a slipped or lost muscle after surgery. This risk may be higher following resection procedures because there is greater tension on the muscle following surgery compared to that for a recessed muscle. This increases the risk that a suture will break or the muscle will be damaged. Loss of a muscle during any strabismus surgery is always problematic. This is particularly so if this complication occurs during resection surgery because recovery is generally more difficult.

10.1.1 Preparation of the Muscle for Resection Once the rectus muscle has been isolated, the intermuscular membrane, muscle capsule, and other fascial tissues are dissected to allow for suture placement posterior to the insertion site of the muscle. During dissection, the surgeon should be careful to avoid penetrating Tenon’s capsule which can promote intrusion of extraconal fat into the operative site. This complication not only makes surgery more difficult, but it can also produce restrictive strabismus that is difficult to repair (Chap. 25).

10.1.2 Resection of the Muscle A second large hook is placed between the muscle and the sclera posterior to the hook that has been used to isolate the muscle insertion. A caliper is used to mark the position of the posterior limit of the resection. We often find it helpful to use a sterile gentian violet skin-marking pen to coat the tip of the caliper prior to this step (>Fig. 10.1a). When the caliper makes contact with the muscle, the ink will be transferred to the muscle surface, facilitating later steps of the procedure. A central safety knot is placed in the muscle at the caliper mark (>Fig. 10.1b). Transverse passes are made, followed by locking bites at the borders of the muscle. A small straight hemostat is placed anterior to the suture and the posterior muscle hook removed. The muscle is then detached from its insertion on the globe (>Fig. 10.2a) and the distal portion of the muscle is excised.

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Fig. 10.1a–c. Measuring and marking the resection. a After coating the tip of the caliber with ink from a sterile gentian violet skin-marking pen, a caliper is used to mark the resection position on the muscle.

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b A central knot is placed at this site, and c transverse passes and locking bites are placed in the muscle and a hemostat is placed anterior to the sutures

Fig. 10.2a,b. Detachment and resection of the muscle. a The muscle is detached from the globe at its insertion and b the distal portion of the muscle is excised.

 

10.1  Technique of Rectus Muscle Resection

During this step, the surgical assistant should ensure that sutures are retracted from the surgical site, to avoid inadvertently cutting them during this step (>Fig. 10.2b). The surgical assistant may place the shaft of a muscle hook across the sutures to help protect them during this step. Some surgeons prefer to cauterize the distal edge of the muscle prior to removal of the hemostat, though this step is not universally necessary. The hemostat can be left in place and used to help hold the muscle in position at the insertion while suturing, if desired.

10.1.3 Reattaching the Muscle to the Sclera The sutures are then passed through the original insertion site of the muscle and the remaining muscle pulled up to the original insertion site. The surgical assistant may facilitate this process by retracting the globe toward the muscle using locking forceps attached to the insertion site to reduce the amount of tension placed on the muscle during this step of the procedure, or the hemostat may be used to hold the muscle in position if it has not yet been removed (>Fig. 10.3). The sutures are then tied and trimmed. Occasionally, the muscle is noted to have retracted posteriorly during the process of tying the sutures. In the event that the muscle does move posteriorly and this is noted after the sutures have been tied, a suture may be passed through each pole of the muscle as needed and brought through the insertion site. The sutures are then tied and cut to bring the muscle back to its proper position (>Fig. 10.4). If the hemostat was left on the muscle, it is removed at this point.

Fig. 10.3. Reattachment of the muscle. The assistant may place anterior traction on the muscle using the hemostat to place the muscle in apposition to the insertion site

10.1.4 Dual Suture Modification We recommend a dual suture modification for large resections and/or in situations where the resected muscle will be placed under a significant amount of tension after it has been sutured to the sclera. A second double-armed suture is secured in the muscle posterior to the primary muscle suture prior to muscle

detachment from the sclera (>Fig. 10.5). The muscle is then secured to the insertion using both of these muscle sutures. This technique is slightly more time-consuming and the additional suture may be cumbersome to work with, but the added security can be of value in selected cases.

Fig. 10.4a–c. Correcting posterior movement of the muscle during resection. a The suture has been tied and the muscle is not in direct contact with the original insertion site. b To correct this, a suture is

passed through the insertion site and behind the muscle suture, and c the newly placed sutures are tied and cut, to bring the muscle to the desired location

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Fig. 10.5. Dual suture technique. Two double-armed sutures are placed in the muscle using a transverse pass and locking bites and the muscle is then secured to the sclera using both of these sutures for added security

Fig. 10.6a,b. Resection clamp technique. a A muscle clamp is placed across the muscle so that the posterior border of the clamp rests at the intended resection site. A double-armed suture is passed through

10.2 Resection Clamp Technique A muscle clamp is placed across the rectus muscle so that the posterior border of the clamp is at the desired resection position (>Fig. 10.6a) and the muscle is detached from the sclera. Two double-armed absorbable sutures are passed through the insertion site of the muscle in an anterior to posterior direction, one at each pole of the insertion site. The sutures are then passed through the muscle, just posterior to the resection clamp . The muscle is advanced anteriorly using the muscle clamp until the muscle just posterior to the clamp is adjacent to the muscle insertion site (>Fig. 10.6b) and the sutures are

each pole of the muscle stump and then through the muscle posterior to the muscle clamp. b The muscle is pulled anteriorly to the insertion and the sutures tied

tied and cut. The resection clamp is removed and the tendon/ muscle anterior to the clamp is excised.

10.3 Rectus Muscle Tuck (Plication) Technique Tucking procedures can be used in place of a rectus muscle resection. Tucking procedures have the potential advantage of preserving the anterior ciliary circulation and reducing the risk of anterior segment ischemia in susceptible patients [1, 2]. A primary disadvantage of the procedure is the bulk of tissue

 

that is produced by the tuck which may be visible under the conjunctiva postoperatively. Two double-armed sutures are placed in the muscle at a position required to create the desired tuck. These two sutures are placed adjacent to each other and include transverse passes, incorporating the entire width of the muscle and locking bites at the borders of the muscle. Care should be taken to avoid disruption of the anterior ciliary vessels as the sutures are placed. The sutures are then passed into the sclera adjacent to each border of the insertion (>Fig. 10.7a). When these sutures are tied together, the effect will be to tuck or fold the portion of muscle anterior to the sutures (>Fig. 10.7b). This muscle fold can be sutured to the remainder of the muscle if desired (>Fig. 10.7c).

Fig. 10.7a–c. Rectus muscle tuck (plication). a After placement of two double-armed sutures in the muscle posterior to the insertion, the sutures are passed into the sclera adjacent to the muscle insertion or

References

References 1.

2.

Park C, Min BM, Wright KW (1991) Effect of a modified rectus tuck on anterior ciliary artery perfusion. Korean J Ophthalmol 5:15–25 Wright KW, Lanier AB (1991) Effect of a modified rectus tuck on anterior segment circulation in monkeys. J Pediatr Ophthalmol Strabismus 28:77–81

through the muscle insertion. b The sutures are tied, c creating a tuck of the anterior portion of the muscle

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Surgery on the Inferior Oblique Muscle

Chapter

11

11 Surgery is performed more commonly on the inferior oblique muscle than on any other cyclovertical muscle. Surgical access to the inferior oblique muscle and procedures designed to alter the effect of contraction of the inferior oblique muscle on the globe are relatively straightforward and complications are infrequent in experienced hands. The most common indications for surgery on the inferior oblique muscle include superior oblique palsy, primary inferior oblique overaction, V-pattern horizontal strabismus with inferior oblique overaction, and dissociated vertical deviation associated with inferior oblique overaction. Accordingly, most operations on the inferior oblique muscle are designed to diminish its function. Weakening procedures on the inferior oblique muscle are numerous and include myotomy, myectomy, recession, marginal myotomy, disinsertion, anterior transposition, and denervation and extirpation. The most recently described weakening operations on the inferior oblique muscle are nasal myectomy and anterior and nasal transposition. The techniques required to perform each of these procedures are reviewed in this chapter. Rarely, a procedure designed to enhance the function of the inferior oblique muscle is required. These unusual indications include persistent or large incyclotorsion and persistent inferior oblique underaction in a patient with an inferior oblique palsy, despite other more traditional surgical approaches. The function of the inferior oblique muscle can be enhanced through advancement of the muscle with or without concurrent resection and by tucking of the belly of the muscle. The techniques for performing these procedures are briefly reviewed.

der of the muscle can usually be identified approximately 10– 12 mm from the limbus. Its path can often be visualized as a deflection created by the muscle and an adjacent fat pad in the overlying intact conjunctiva in the inferotemporal quadrant (>Fig. 11.1). When making a conjunctival incision for surgery on the inferior oblique muscle, many surgeons prefer to place the incision more posterior than a standard fornix incision, feeling that access to the surgical space is enhanced. If this approach is used, the surgeon should avoid placing the incision over the fat pad located in the inferotemporal quadrant of the orbit (>Fig. 11.1), because violation of this fat pad can result in intrusion of orbital fat into the operative site, compromising visualization during surgery, producing bleeding, and resulting in postoperative fat adherence syndrome (Chap. 25). Many techniques are possible for visually identifying and surgically isolating the inferior oblique muscle once the conjunctival and Tenon’s capsule incisions have been created. Techniques that first identify and isolate the lateral rectus muscle help to both simplify the process of surgical isolation of the inferior oblique muscle and reduce the risk that the lateral rectus muscle will be inadvertently isolated rather than the inferior oblique muscle (Chap. 25).

11.1 Identification and Isolation of the Inferior Oblique Muscle All surgical procedures commonly performed on the inferior oblique muscles are conducted on the distal half of the muscle. Techniques for identification and isolation of the inferior oblique muscle along its proximal half are described later. Access to the distal portion of the inferior oblique muscle is gained through a standard fornix conjunctival incision, and incision through Tenon’s capsule in the inferotemporal conjunctival quadrant as described in Chap. 8. The inferior oblique muscle itself is located in Tenon’s capsule. The anterior bor-

Fig. 11.1. Inferior oblique muscle and surrounding fascia and inferotemporal orbital fat pad visualized through the intact conjunctiva

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Good exposure of the surgical site is important for all operations, but is particularly important for surgery on the inferior oblique muscle. The location of the insertion of the inferior oblique muscle in the posterior orbit, the presence of surrounding orbital fat, and proximity of the muscle belly to a vortex vein in the inferotemporal quadrant all present areas of significant surgical risk when exposure is suboptimal. Exposure of the surgical site and positioning of the eyes can be facilitated through several techniques. Use of a bridle suture around the lateral rectus muscle is a very effective means of gaining superior surgical exposure. The lateral rectus muscle insertion is isolated on a Gass muscle

hook (Chap. 7). There is a hole in the toe of the Gass muscle hook, making placement of a bridle suture simple and safe. After hooking the lateral rectus muscle, the toe of the Gass muscle hook is directed anteriorly, tenting the conjunctiva. A 4-0 silk suture is passed through the conjunctiva and the hole in the toe of the Gass muscle hook (>Fig. 11.2a). The suture is then withdrawn through the conjunctiva and behind the lateral rectus muscle insertion (>Fig. 11.2b). The globe is then retracted upward and nasally and fixed in this position by attaching the bridle suture to the surgical drapes with a hemostat. Retracting the globe to this position directs the belly of the inferior oblique muscle anteriorly and greatly facilitates identification and isolation of the muscle. One or two large hooks are then placed deeply into the incision which is retracted inferiorly by the assistant surgeon (>Fig. 11.2c). The surgeon visually inspects Tenon’s capsule, which has been retracted inferiorly in an effort to identify the inferior oblique muscle (>Fig. 11.2c). Identification of the

Fig. 11.2a–c. Exposure of the surgical site for inferior oblique muscle surgery using a lateral rectus muscle bridle suture (surgeon’s view). a A Gass muscle hook is placed behind the lateral rectus muscle insertion and a 4-0 silk suture is passed through a hole in the toe of the hook. b The suture is withdrawn behind the lateral rectus muscle insertion, the globe retracted upward and nasally, and the bridle attached to the sur-

gical drapes using a hemostat to maintain this position of the globe. c One or two hooks are placed into the incision and retracted inferiorly. The inferior oblique muscle can be seen in Tenon’s capsule. Important landmarks that can aid in identification of the inferior oblique muscle include visualization of the border of the inferior oblique muscle, the sclera, and a vortex vein simultaneously

11.1.1 Technique 11.1.1.1 Exposure of the Surgical Site

 

muscle can be facilitated by retraction of the globe slightly superiorly using a small muscle hook.. The posterior border of the inferior oblique muscle should be easily identified. Important landmarks that can aid the surgeon in confirming that the posterior border of the inferior oblique muscle has been identified include visualization of the posterior border of the inferior oblique muscle, the sclera, and the adjacent vortex vein simultaneously (>Fig. 11.2c). Alternatively, some surgeons gain exposure to the surgical site by placement of a hook behind the insertion of the lateral and inferior rectus muscles. These two hooks are held in position by an assistant surgeon (>Fig. 11.3) while the surgeon identifies the inferior oblique muscle as described above. A disadvantage of this technique is that both hands of the assistant surgeon are occupied holding these muscle hooks, so that the assistant surgeon is not available to help with other tasks during isolation of the muscle.

11.1  Isolation of the Inferior Oblique

11.1.1.2 Isolating the Muscle on a Muscle Hook A Scobee muscle hook or Steven’s muscle hook (we prefer a Scobee muscle hook) is passed beneath the border of the inferior oblique muscle, directed first toward the floor of the orbit and then drawn gently anteriorly (>Fig. 11.4). This maneuver should not be thought of as a “blind sweep.” Rather, the surgeon should clearly visualize the posterior border of the inferior oblique muscle followed by careful placement of the hook and methodical movements inferiorly and anteriorly to isolate the muscle. With experience, the surgeon develops a “feel” for the technique, allowing isolation of the entire muscle without associated orbital fat and other adjacent tissues. An optional step in the surgical isolation of the inferior oblique muscle is gentle blunt dissection of the border between the posterior margin of the inferior oblique muscle and Tenon’s capsule. This maneuver aids in the placement of a hook under the posterior border of the muscle.

11.1.1.3 Dissection of the Capsule of the Inferior Oblique Muscle

Fig. 11.3. Exposure of the surgical site for inferior oblique muscle surgery using muscle hooks behind the lateral and inferior rectus muscles

The surgical assistant should place the belly of the inferior oblique muscle under mild anterior traction with the Scobee hook and simultaneously retract the incision temporally. This combined maneuver places Tenon’s fascia and the capsule of the inferior oblique muscle under mild traction as well. The surgeon then sharply dissects the capsule to expose the inferior oblique muscle insertion on the sclera temporally (>Fig. 11.5). Care should be taken to avoid the inferotemporal vortex vein and to avoid violation of posterior Tenon’s capsule, which can result in intrusion of orbital fat into the operative site (Chap. 25).

Fig. 11.4. Isolating the inferior oblique muscle on a muscle hook. A Scobee muscle hook is placed at the posterior border of the inferior oblique muscle. The hook is gently advance inferiorly and then anteriorly, to bring only the inferior oblique muscle anteriorly on the hook

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Chapter 11

Fig. 11.5a,b. Dissection of the muscle capsule of the inferior oblique: a exposure of the hook, followed by b sharp dissection of the muscle capsule while the assistant surgeon places the capsule under mild traction

11.2 Weakening Procedures on the Inferior Oblique Muscle As noted earlier, the vast majority of procedures performed on the inferior oblique muscle are designed to limit its function on the globe. Many inferior-oblique-weakening procedures can be used to treat a wide range of deviations without the need to precisely titrate surgery to specific measurements obtained in the office. Some have characterized many surgical procedures on the inferior oblique muscle as “self adjusting.” For example, the same inferior oblique muscle recession

done to treat a superior oblique paresis may be just as effective if there is a hypertropia of 14 prism diopters as it is for a hypertropia of 5 prism diopters. Weakening procedures on the inferior oblique muscles are generally accomplished with few serious complications. Most of the complications that can occur during inferior oblique muscle surgery occur during the steps to isolate the muscle and dissect its capsule. Much of the decision for choosing a particular procedure is dependant on the training and experience of the surgeon. Our usual procedure of choice for inferior oblique muscleweakening procedures is loosely outlined in Table 11.1. Many surgeons prefer inferior oblique recessions to disinsertion,

  Table 11.1. Choices of inferior-oblique-weakening procedure based on surgical indications Degree of inferior oblique overaction

Surgical options (authors’ usual preference listed first)

1+

Observation, or Marginal myotomy, or Full myotomy

2+

Recession, or Disinsertion, or Myectomy, or Full myotomy

3+

Recession, or Disinsertion, or Myectomy

4+

Myectomy, or Recession, or Anterior transposition

Significant residual overaction after myectomy or recession

Denervation and extirpation

Any overaction and dissociated vertical deviation

Anterior transposition

11.2  Inferior Oblique Weakening Procedures

myectomy, and myotomy because these other procedures, unlike recessions, may be associated with reattachment of the inferior oblique muscle insertion back to the sclera in an unpredictable location [1] (>Fig. 11.6). Not only can this result in recurrence of inferior oblique overaction after surgery, but it also makes reoperations more difficult. Several techniques have been described to prevent this complication as outlined in Chap. 25.

11.2.1 Technique of Inferior Oblique Muscle Recession Following exposure and isolation of the muscle and dissection of the muscle capsule as reviewed above, the inferior oblique muscle is detached from the sclera at its insertion. Two techniques can be utilized. A hemostat can be placed across the inferior oblique muscle several millimeters proximal to its insertion into the sclera (>Fig. 11.7a). Scissors are then used to transect the inferior oblique muscle between the hemostats and muscle insertion. Cautery may be applied to the proximal muscle edge to prevent bleeding following the removal of the hemostat, although this often is not necessary. Absorbable suture such as 6-0 polyglactin suture is then placed in the muscle adjacent to the hemostat (>Fig. 11.7b). The muscle is then sutured to the sclera along the normal course of the inferior oblique muscle. We most commonly place the anterior muscle suture 2–4 mm posterior to the temporal border of the inferior rectus muscle insertion, a position which places it just anterior to a vortex vein exit from the sclera in this area (>Fig. 11.7c). The muscle can be placed in other positions at the discretion of the surgeon. The conjunctiva is then closed with interrupted absorbable suture. Alternatively, the inferior oblique muscle insertion can be dissected from the sclera directly by cutting the muscle flush with the sclera. Cautery is applied to the distal edge of the muscle and absorbable sutures are placed in the distal end of the muscle. The practice of placing sutures in the muscle prior to disinsertion of the muscle from the sclera is cumbersome, unnecessary, and generally requires resection of a substantial portion of the distal part of the muscle.

11.2.1.1 Graded Inferior Oblique Recession

Fig. 11.6. Position of reattachment of the inferior oblique muscle to the globe after myectomy in monkey eyes. (Reprinted from [1] Ar­ chives of Ophthalmology, volume 95, Wertz RD, Romano PE, Wright P. Inferior oblique myectomy, disinsertion, and recession in rhesus monkeys, page 859, 1977, with permission from American Academy of Ophthalmology)

In our experience, graded recession of the inferior oblique muscle is unnecessary in most cases, and the surgical results are similar regardless of where the new inferior oblique muscle insertion is placed (within excepted standards) except when the new insertion is significantly advanced anteriorly. Some surgeons, however, titrate recessions of the inferior oblique muscle depending on the severity of the inferior oblique overaction. Figure 11.8 demonstrates possible placement of the new muscle insertion if the surgeon believes that titration of surgical effect is warranted.

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Fig. 11.7a–c. Inferior oblique recession. a The muscle is transected distal to a hemostat placed across the muscle near the insertion. b Cautery is applied to the proximal muscle edge and absorbable sutures placed in the muscle adjacent to the hemostat. c The muscle is sutured to the

Chapter 11

sclera; the anterior suture is most commonly placed 2–4 mm posterior to the temporal border of the inferior rectus muscle. Note the vortex vein just behind this location

 

11.2  Inferior Oblique Weakening Procedures

Fig. 11.8a–d. Titrated or graded recession and/or anteriorization of the inferior oblique muscle for a mild to moderate, b moderate, c moderate to marked, and d severe inferior oblique muscle overaction

11.2.2 Technique of Inferior Oblique Muscle Disinsertion Some surgeons prefer simple disinsertion of the inferior oblique muscle without suturing the distal end of the muscle back to the sclera. One potential problem with such an approach is that the muscle may become reattached to the sclera in an unpredictable location, resulting in recurrence of unwanted inferior oblique muscle function [1]. After exposure, isolation and dissection of the muscle capsule, the inferior oblique muscle is disinserted from the sclera using the technique of choice. Cautery may be applied to the cut edge of the muscle, the muscle released, and the conjunctiva closed with absorbable suture (>Fig. 11.9).

11.2.3 Technique of Inferior Oblique Myectomy Myectomy of the inferior oblique muscle is an effective procedure for limiting the function of the inferior oblique muscle. The indications for this procedure are similar to the indications for an inferior oblique muscle recession, though we tend to reserve myectomy for patients with pronounced inferior oblique overaction. The advantages of an inferior oblique myectomy include limited time required for surgery, simplicity, and the fact that sutures are not placed in the sclera, essentially eliminating the risk of endophthalmitis that is present when sutures are placed in the sclera (Chap. 22). Potential disadvantages of an inferior oblique myectomy include reattachment of

Fig. 11.9. Disinsertion of the inferior oblique muscle. The inferior oblique muscle is disinserted from the sclera, cautery is applied to the cut edge of the muscle, and the conjunctiva closed with absorbable suture

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the muscle to the sclera at an unpredictable location postoperatively [1] which can result in recurrence of unwanted inferior oblique function. Reoperations on the inferior oblique muscle may also be more difficult following myectomy procedures because of scarring and because the final location of the distal end of the muscle is not known. After exposure, isolation, and dissection of the capsule of the inferior oblique muscle, two hemostats are placed across the inferior oblique muscle separated by approximately 5–10 mm (>Fig. 11.10a). Muscle between the hemostats is excised, discarded, and cautery is applied to the cut edges of the muscle (>Fig. 11.10b). The muscle is then released and the proximal segment of the muscle is allowed to retract into Tenon’s capsule. Some surgeons prefer to suture Tenon’s capsule closed after the muscle has retracted into Tenon’s capsule to reduce the chance that the muscle will reattach to the sclera. The conjunctiva is then closed with interrupted absorbable suture.

Fig. 11.10a,b. Inferior oblique myectomy. a Two hemostats are placed across the muscle, separated by 5–10 mm. b The myectomy is performed , the muscle edges cauterized

Chapter 11

11.2.4 Technique of Inferior Oblique Myotomy Marginal or complete myotomy of the inferior oblique muscle can be performed to weaken the function of the inferior oblique muscle. A complete myotomy is considered by some surgeons to be as effective as myectomy or recession of the inferior oblique muscle. Some surgeons perform marginal myotomy on the inferior oblique muscle for mild inferior oblique overaction. To perform a complete myotomy, one or two hemostats are placed across the inferior oblique muscle. The muscle is then transected and cautery may be applied to the cut edges of the muscle. The hemostat(s) is removed, the surgical site inspected to ensure that no active bleeding is present, and the conjunctiva is closed with interrupted absorbable suture (>Fig. 11.11a). A marginal myotomy requires the creation of overlapping partial myotomies of the inferior oblique muscles ranging from 60% to 75% of the muscle’s width. A hemostat is placed across the muscle at the site of the planned marginal myotomy and removed after 30–60 s. The marginal myotomy is then performed along the area crushed by the hemostat and cautery applied (>Fig. 11.11b). In order for a marginal myotomy to be effective, all fibers of the muscle must be cut in overlapping myotomies [2]. We have not found a satisfactory indication for marginal myotomy of the inferior oblique muscle, usually preferring observation alone for eyes with mild inferior oblique overaction that would be most appropriate for consideration of a marginal myotomy procedure.

Fig. 11.11a,b. Inferior oblique myotomy. a Complete myotomy, and b marginal myotomy

 

11.2  Inferior Oblique Weakening Procedures

11.2.5 Technique of Denervation and Extirpation Denervation and extirpation of the inferior oblique muscle is an infrequently used procedure. It is reserved for the most pronounced overaction of the inferior oblique muscle and many surgeons reserve the procedure for significant recurrent inferior oblique overaction despite previous weakening procedures on the inferior oblique muscle. The procedure involves identification and transection of the neurovascular bundle combined with removal of a large distal segment of inferior oblique muscle. An experienced surgical assistant is helpful in performing this procedure because exposure of the surgical site is difficult. The inferior oblique muscle is isolated and detached from the globe through a standard incision in the inferotemporal conjunctival quadrant. Mild anterior traction is placed on the muscle and sharp dissection of the muscle capsule done in a nasal direction (>Fig. 11.12a). A fusiform expansion on the posterior side of the inferior oblique muscle near the lateral border of the inferior rectus muscle represents the neurovascular bundle, where a branch of the third cranial nerve and the vascular supply for the inferior oblique muscle enter the muscle [3]. A small hook, such as a Steven’s hook, is used to grasp the neurovascular bundle and place it under mild traction (>Fig. 11.12b). A hemostat is placed across the neurovascular bundle and cautery applied to cut and coagulate the neurovascular bundle anterior to the clamp (>Fig. 11.12c). If the neurovascular bundle has been completely severed, the muscle insertion can be advanced anteriorly (>Fig. 11.12d). A hemostat is then placed on the inferior oblique muscle as close to the muscle’s origin as possible, and the large distal portion of the muscle (representing most of the inferior oblique muscle) distal to the hemostat is excised, and cautery is applied to the proximal edge of the muscle for hemostasis (>Fig. 11.12e). The muscle stump is then allowed to retract into the posterior Tenon’s capsule. The capsule can be optionally closed with absorbable suture.

11.2.6 Technique of Inferior Oblique Anterior Transposition Anterior transposition of the inferior oblique muscle is performed in exactly the same manner as an inferior oblique recession procedure, with the exception that the new muscle insertion is located well anterior to the equator rather than along the normal course of the inferior oblique muscle. Anterior transposition of the inferior oblique muscle is an excellent procedure when needed and has several specific indications. The most common indication for the inferior oblique anterior transposition procedure is the treatment of dissociated vertical deviation and significant inferior oblique overaction in the same eye. Though the procedure is most commonly performed bilaterally, it can be performed unilaterally with caution [4–6]. Unilateral inferior oblique overaction can result in asymmetry of the lower eyelid that can be bothersome to patients (Chap. 26),

Fig. 11.12a–e. Denervation and extirpation. a After detachment of the inferior oblique muscle from the globe at its insertion, mild anterior traction is placed on the muscle. b A small hook is used to grasp the neurovascular bundle and place it under mild traction

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Chapter 11

Fig. 11.12a–e. (continued) Denervation and extirpation. c Cautery is used to cut and coagulate the neurovascular bundle. d The muscle can be advanced significantly further anteriorly if the neurovascular bundle has been completely transected. e A hemostat is then placed on the inferior oblique muscle as close to the muscle origin as possible, and a large distal portion of the muscle is removed. Cautery is applied for hemostasis and the muscle stump allowed to retract into posterior Tenon’s capsule

Other less common indications have included treatment of unilateral superior oblique palsy [7], lost [8], ruptured [9, 10] or absent [11] inferior rectus muscles, V-pattern horizontal strabismus [12, 13], and hypertropia with marked inferior oblique overaction [6]. Parvataneni and Olitsky [4] reported use of inferior oblique muscle anterior transposition and resection to treat a hypertropia in patients at significant risk for anterior segment ischemia.

After exposure, isolation, dissection of the muscle capsule, and disinsertion of the inferior oblique muscle at its insertion, the inferior oblique muscle insertion is reattached to the sclera near the temporal border of the inferior rectus muscle insertion. It is generally placed no more than 1 mm anterior or posterior to the insertion, and is most commonly placed at the level of the insertion (>Fig. 11.13a). Unlike inferior oblique recession, in which the new insertion is spread out to the nor-

 

mal width of the inferior oblique tendon, the insertion is usually clustered adjacent to the inferior rectus muscle insertion (>Fig. 11.13b). Suturing the inferior oblique muscle too far anterior to the inferior rectus muscle or spreading the insertion out too broadly has been suggested as a cause of unwanted restrictive strabismus following surgery [14]. The conjunctiva is then closed with interrupted absorbable sutures. It is not uncommon for physicians and/or patients to be aware of subtle and sometimes obvious changes in the contour of the lower eyelid following inferior oblique anterior transposition [15] (Chap. 26).

11.2.7 Technique for Nasal Myotomy of the Inferior Oblique Muscle Stager and coworkers [16] reported a technique for nasal myotomy of the inferior oblique muscle for recurrent inferior oblique overaction. The procedure involves removal of a 5-mm segment from the nasal portion of the inferior oblique muscle, leaving the remaining temporal portion of the muscle and the neurovascular junction intact. These authors reported reduction in residual inferior oblique overaction in 95% of patients, with complete elimination of overaction in many patients. An inferonasal fornix conjunctival incision is made and carried down to bare sclera. The inferior rectus muscle is isolated from its nasal border and the eye retracted superiorly. The inferior oblique muscle is identified in Tenon’s capsule and is seen to abruptly narrow nasal to the inferior rectus muscle. The nasal portion of the inferior oblique muscle is isolated on one or two small hooks Two hemostats separated by approximately 5 mm are placed across the muscle and the segment of muscle between the hemostats removed with sharp dissection. The cut edges of the muscle are cauterized and the distal segment of muscle is placed into the posterior Tenon’s capsule. Any openings seen in Tenon’s capsule are sutured closed to reduce the risk of fat intrusion into the surgical site. The conjunctiva is closed with absorbable suture.

11.2  Inferior Oblique Weakening Procedures

felt the procedure was particularly successful in patients with recurrent congenital or acquired superior oblique palsy, particularly as a secondary procedure. After exposure, isolation, and dissection of the distal portion of the inferior oblique muscle in the inferotemporal orbit, the insertion of the muscle is transposed inferior to the inferior rectus muscle to the nasal side of the inferior rectus muscle. The posterior-temporal fibers are sutured 2 mm nasal and 2 mm posterior to the nasal border of the inferior rectus muscle insertion and the anterior-temporal fibers are sutured 3 mm nasal to this position (>Fig. 11.14). Nonabsorbable sutures are recommended for securing the muscle to the sclera, because the posterior-temporal fibers of the muscle are under enough tension to slip after the tensile strength of absorbable sutures is lost.

Fig. 11.13a,b. Inferior oblique muscle anterior transposition. a The new insertion of the muscle is placed 1 mm anterior or posterior and adjacent to the temporal border of the inferior rectus muscle insertion. b The insertion should not be spread out, as this can result in unwanted duction abnormalities postoperatively

11.2.8 Technique for Anterior and Nasal Transposition of the Inferior Oblique Muscle Stager and coworkers [17, 18] reported anterior and nasal transposition of the inferior oblique muscle. The procedure was utilized on patients with inferior oblique overaction, superior oblique palsy, absent superior oblique muscles, anti-elevation syndrome, and Duane syndrome with significant upshoots and downshoots in adduction. All of their patients had one or more of the following signs including overelevation in adduction, exotropia in up gaze, an abnormal head posture, and/or excyclotorsion. The procedure was said to work favorably in all patients except those with Y-pattern exotropia. The procedure was found to eliminate up shoots in Duane syndrome, but shown to worsen down shoots in some patients. These authors

Fig. 11.14. Anterior and nasal transposition of the inferior oblique muscle. After isolating and disinserting the muscle in the inferotemporal quadrant of the orbit, the posterior-temporal fibers are sutured 2 mm nasal and 2 mm posterior to the nasal border of the inferior rectus muscle insertion and the anterior-temporal fibers are sutured 3 mm nasal to this position using nonabsorbable sutures

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11.3 Strengthening Procedures on the Inferior Oblique Muscle Procedures to enhance the function of the inferior oblique muscle are rarely indicated. However, such procedures might be indicated in two particular situations. The first is severe incyclotorsion or residual incyclotorsion despite attempted surgical correction by other means. Freedman and coworkers [19, 20] reported use of inferior oblique advancement combined with superior oblique tenotomy to treat incyclotorsion caused by macular translocation surgery. The second possible indication is persistent inferior oblique underaction in patients with inferior oblique muscle palsy despite previous surgical intervention. It should be noted that some people consider anterior transposition of the inferior oblique muscle to be a “strengthening” procedure of the inferior oblique muscle.

Chapter 11

11.3.2 Technique for Tucking Procedure on the Inferior Oblique Muscle After exposure, isolation, and dissection of the capsule, a tucking procedure can be performed. The muscle is tucked by passing 6-0 absorbable or nonabsorbable suture to plicate the muscle in the inferotemporal quadrant of the orbit (>Fig. 11.16).

11.3.1 Technique for Advancement of the Inferior Oblique Muscle With and Without Resection After exposure, isolation, dissection, and disinsertion of the inferior oblique muscle at its insertion as described above, the inferior oblique muscle is advanced distally, parallel to its normal course along the globe. It is then reinserted into the sclera typically at or above the border of the lateral rectus muscle (>Fig. 11.15). Resection of the distal end of the inferior oblique muscle ranging from approximately 5 mm to 10 mm can be done to further enhance the effect of the procedure. The conjunctiva is closed with interrupted absorbable suture.

Fig. 11.15. Advancement of the inferior oblique muscle with and without resection. The inferior oblique muscle is advanced forward, parallel with its normal course, and sutured to the sclera above the

Fig. 11.16. Tucking procedure of the inferior oblique muscle. The muscle is tucked using 6-0 absorbable or nonabsorbable suture to plicate the muscle

lateral rectus muscle border. A small to medium resection can be performed to enhance the effect of the advancement

 

References 1.

Wertz RD, Romano PE, Wright P (1977) Inferior oblique myectomy, disinsertion, and recession in rhesus monkeys. Arch Ophthalmol 95:857–860 2. Helveston EM, Cofield DD (1970) Indications for marginal myotomy and technique. Am J Ophthalmol 70:574–578 3. Stager DR (1996) The neurofibrovascular bundle of the inferior oblique muscle as its ancillary origin. Trans Am Ophthalmol Soc 94:1073–1094 4. Parvataneni M, Olitsky SE (2005) Unilateral anterior transposition and resection of the inferior oblique muscle for the treatment of hypertropia. J Pediatr Ophthalmol Strabismus 42:163–165 5. Bothun ED, Summers CG (2004) Unilateral inferior oblique anterior transposition for dissociated vertical deviation. J AAPOS 8:259–263 6. Goldchmit M, Felberg S, Souza-Dias C (2003) Unilateral anterior transposition of the inferior oblique muscle for correction of hypertropia in primary position. J AAPOS 7:241–243 7. Gonzalez C, Cinciripini G (1995) Anterior transposition of the inferior oblique in the treatment of unilateral superior oblique palsy. J Pediatr Ophthalmol Strabismus 32:107–113 8. Olitsky SE, Notaro S (2000) Anterior transposition of the inferior oblique for the treatment of a lost inferior rectus muscle. J Pediatr Ophthalmol Strabismus 37:50–51 9. Chang YH, Yeom HY, Han SH (2005) Anterior transposition of the inferior oblique muscle for a snapped inferior rectus muscle following functional endoscopic sinus surgery. Ophthalmic Surg Lasers Imaging 36:419–421 10. Aguirre-Aquino BI, Riemann CD, Lewis H, Traboulsi EI (2001) Anterior transposition of the inferior oblique muscle as the initial treatment of a snapped inferior rectus muscle. J AAPOS 5:52–54

References 11. Gamio S, Tartara A, Zelter M (2002) Recession and anterior transposition of the inferior oblique muscle [RATIO] to treat three cases of absent inferior rectus muscle. Binocul Vis Strabismus Q 17:287–295 12. Polati M, Gomi C (2002) Recession and measured, graded anterior transposition of the inferior oblique muscles for V-pattern strabismus: outcome of 44 procedures in 22 typical patients. Binocul Vis Strabismus Q 17:89–94 13. Minguini N, de Carvalho KM, de Araujo L, Crosta C (2004) Anterior transposition compared to graded recession of the inferior oblique muscle for V-pattern strabismus. Strabismus 12:221–225 14. Kushner BJ (1997) Restriction of elevation in abduction after inferior oblique anteriorization. J AAPOS 1:55–62 15. Kushner BJ (2000) The effect of anterior transposition of the inferior oblique muscle on the palpebral fissure. Arch Ophthalmol 118:1542–1546 16. Stager DR Jr., Wang X, Stager DR Sr., Beauchamp GR, Felius J (2004) Nasal myectomy of the inferior oblique muscles for recurrent elevation in adduction. J AAPOS 8:462–465 17. Stager DR Jr., Beauchamp GR, Wright WW, Felius J, Stager D Sr (2003) Anterior and nasal transposition of the inferior oblique muscles. J AAPOS 7:167–173 18. Stager DR Sr., Beauchamp GR, Stager DR Jr. (2001) Anterior and nasal transposition of the inferior oblique muscle: a preliminary case report on a new procedure. Binocul Vis Strabismus Q 16:43–44 19. Freedman SF, Rojas M, Toth CA (2002) Strabismus surgery for large-angle cyclotorsion after macular translocation surgery. J AAPOS 6:154–162 20. Freedman SF, Seaber JH, Buckley EG, Enyedi LB, Toth CA (2000) Combined superior oblique muscle recession and inferior oblique muscle advancement and transposition for cyclotorsion associated with macular translocation surgery. J AAPOS 4:75–83

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Surgery on the Superior Oblique Tendon

12

12 Surgical procedures involving the superior oblique tendon are among the most intricate surgical procedures performed by the strabismus surgeon. Both the complex functions of the superior oblique muscle and its complex anatomical configuration make surgery on the superior oblique tendon unforgiving when proper indications and techniques are not carefully followed [1, 2]. Postoperative problems are often difficult to satisfactorily remedy. However, with careful consideration of the indications for surgery as well as meticulous detail to surgical technique, the results of surgery can be very satisfying. The functions of the superior oblique muscle/tendon can be enhanced or reduced. The broad insertion of the superior oblique tendon into the sclera, as well as the anatomy of the insertion relative to the equator of the globe and the functional origin of the muscle in the superonasal aspect of the orbit result in the ability to alter specific functions of the superior oblique muscle/tendon by manipulation of different portions of the superior oblique tendon and its insertion. The anterior fibers of the superior oblique tendon, which course temporally from the superonasal aspect of the orbit, are anterior to the equator of the globe. They are thought to be primarily responsible for incycloduction of the globe (Chap. 2). The posterior fibers course posterior to the equator and are primarily responsible for depression and abduction. Because of its unique anatomy and surgery, physiology can be used to selectively weaken or strengthened a specific function(s) of the superior oblique muscle.

12.1 Forced Traction Testing of the Superior Oblique Tendon Both forced traction testing and exaggerated forced traction testing are a useful adjunct during surgery on the superior oblique tendon (>Fig. 12.1). It can be very useful in identifying a lax superior oblique tendon, which commonly occurs in congenital superior oblique palsies [3–5] and the finding of a very lax superior oblique tendon may prompt the surgeon to consider a tucking procedure. Saunders and Tomlison [6] and Saunders [7] reported that, in order to avoid producing a large Brown syndrome after a superior oblique tendon tucking procedure, the surgeon should perform a traction test to help titrate the size of the tuck. Exaggerated forced traction testing of the superior oblique tendon is reviewed in detail in Chap. 8.

Fig. 12.1. Traction testing to measure laxity or tightness of the superior oblique tendon. Surgeon’s view

12.2 Superior-ObliqueStrengthening Procedures Superior-oblique-strengthening procedures can be performed on the anterior portion of the tendon or on the full width of the tendon through tucking procedures. Tucking of the full width of the tendon tightens both the anterior and posterior tendon fibers and will therefore increase the impact of all three functions of the superior oblique muscle including incycloduction, depression, and abduction. Tucking of only the anterior fibers of the tendon selectively increases the incycloduction function of the superior oblique muscle and is used when excyclotorsion is the primary problem.

12.2.1 Technique of Superior Oblique Tucking Procedure A tuck of the superior oblique tendon is designed to enhance all three functions of the superior oblique muscle. It may be performed for the treatment of superior oblique palsy as an isolated procedure or be combined with a weakening procedure of another cyclovertical muscle such as the ipsilateral inferior oblique, ipsilateral superior rectus or contralateral in-

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ferior rectus muscle. Following a tuck of the superior oblique tendon, some degree of iatrogenic limitation of elevation in adduction (referred to loosely as Brown syndrome) frequently occurs [8] and is usually required to achieve surgical success. Brown syndrome is less likely to occur when a superior oblique tuck is performed alone than when done in conjunction with a weakening procedure of the ipsilateral inferior oblique muscle [9]. The severity of the induced Brown syndrome can be minimized in two ways. A tucking procedure of the superior oblique tendon on the nasal side of the superior rectus muscle will generally produce a more significant restriction, and therefore tucking procedures are more commonly performed on the temporal aspect of the tendon near the insertion of the tendon into the sclera. Second, prior to tying permanent knots in the suture used to perform the tuck, traction testing can be performed to evaluate the tightness of the tucked tendon. If the tendon is found to be too tight, the tuck can be reduced accordingly. While we have found that many patients will demonstrate some degree of Browns syndrome after a superior oblique tuck, few are bothered by it. The exchange of single vision in side gaze, down gaze and relief of torticollis for a minimal degree of diplopia in adduction and elevation is acceptable to most patients. We have frequently noted that failure to produce some degree of restriction to elevation in adduction often, if not usually, results in undercorrection of the deviation.

Chapter 12

12.2.1.1 Identifying the Superior Oblique Tendon The superior rectus muscle is isolated using either a limbal or fornix approach (usually a fornix approach). Following isolation of the superior rectus muscle, a small muscle hook is used to retract the conjunctiva and Tenon’s fascia posteriorly along the lateral edge of the superior rectus muscle (>Fig. 12.2a). A small amount of dissection of the epimuscular fascia above the superior rectus muscle may facilitate exposure. A retractor can be placed in the posterior aspect of the incision to improve exposure of the temporal border of the superior rectus muscle as well as the superior oblique tendon. The insertional fibers of the superior oblique tendon can usually be easily identified traveling underneath the superior rectus muscle and fanning out to insert into the sclera posteriorly on the temporal side of the superior rectus muscle (>Fig. 12.2b).

12.2.1.2 Isolation of the Superior Oblique Tendon A small hook is placed on the sclera adjacent to the temporal border of the superior rectus muscle and anterior to the superior oblique tendon. The small hook is moved posteriorly as it is held against the sclera. It is then turned superiorly and with-

Fig. 12.2a,b. Identification of the superior oblique tendon. a After isolation of the superior rectus muscle, a small muscle hook and retractor are used to improve exposure, b allowing visualization of the superior oblique tendon on the temporal side of the superior rectus muscle

 

12.2  Superior-Oblique-Strengthening Procedures

drawn anteriorly, resulting in isolation of the superior oblique tendon (>Fig. 12.3). A vortex vein is usually visible near the insertion of the tendon into the sclera and provides a good landmark. The small hook can be exchanged for a larger hook that will more securely maintain control of the tendon. Attachments between the superior oblique tendon and superior rectus muscle can be bluntly dissected if needed.

12.2.1.3 Tucking of the Superior Oblique Tendon The tendon is engaged on a tendon tucker and the desired size of the tuck dialed into the tucker (>Fig. 12.4a). The amount of tuck that is being performed can be read from the calibration markings on the tucking device. The calibration markings represent the length of each arm of the tuck. Therefore, the total tuck represents twice the amount indicated by the calibration marks. We generally report a tuck as follows so that it is clear to us later what we have done. If a 10-mm tuck has been performed (calibration marking 5 mm), we will denote this as a tuck of 5 + 5= 10. The size of the tuck required is dictated by the magnitude of the hypertropia in the primary position and by the degree of tendon laxity. Many cases of congenital superior oblique palsy demonstrate significant tendon laxity [3, 4] and require large tucks. In contrast, acquired palsies generally require only small tucks. We initially titrate the tuck to include

Fig. 12.4a–d. Tucking the superior oblique tendon with a tucking device. a The tendon is engaged on a tendon tucker and the desired size of the tuck dialed into the tucker. b A nonabsorbable suture is passed through the tendon to plicate the base of the tuck. c The base of the

Fig. 12.3a,b. Isolating the superior oblique tendon. a A small hook is drawn anteriorly as it is held against the sclera posterior to the superior oblique tendon, resulting in isolation of the superior oblique tendon. b The small hook is exchanged for a larger hook

tucked tendon should be examined to ensure that the knot is tight. d The tucked portion of the tendon can then be sutured to the sclera, if desired

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Chapter 12

the amount of tendon necessary to bring the base of the tuck close to the surface of the globe while placing mild anterior traction on the tendon. A nonabsorbable suture is passed through the mid portion of the tendon inferior to the tucking device to plicate the base of the tuck (>Fig. 12.4b). We prefer the use of a 5-0 or 6-0 Mersilene suture. The suture can be tied temporarily or permanently depending on whether the surgeon will perform traction testing to assess the tightness of the tucked tuck. After completing the tuck and tying a permanent knot in the suture, the base of the tucked tendon should be examined to ensure that the knot is tight (>Fig. 12.4c). The tucked portion of the tendon can then be sutured to the sclera (>Fig. 12.4d) or simply allowed to retract back into the episcleral space. If a tendon tucker is not available, the tendon can be folded on itself and a hemostat can be placed across the folded tendon at its base, followed by placement of a suture to plicate the tendon (>Fig. 12.5).

12.2.2 Technique for the Fells Modification of the Harada-Ito Procedure The Fells modification of the Harada-Ito procedure is used to correct excyclotorsion, most often in the setting of a bilateral superior oblique palsy with minimal vertical deviation in the primary position [10, 11]. The procedure involves advancement of the anterior portion of the superior oblique tendon. These fibers run relatively parallel with the equator of the globe and are primarily responsible for incycloduction of the globe. After isolation of the superior oblique tendon on the temporal side of the superior rectus muscle, two small muscle hooks are used to divide the superior oblique tendon longitudinally extending from its insertion into the sclera for ap-

Fig. 12.6a,b. Fells modification of the Harada-Ito procedure. a The superior oblique tendon is split longitudinally, separating the anterior 25% of the tendon from the remainder of the tendon and an absorbable suture is secured in the anterior tendon fibers, which are then

Fig. 12.5. Tucking the superior oblique tendon without using a tucking device

detached from the sclera. b The detached portion of the tendon is sutured to the sclera 8 mm posterior and 2 mm superior to the superior edge of the lateral rectus muscle insertion

 

proximately 8–10 mm proximally. The anterior 25% of the tendon fibers are separated from the remainder of the tendon (>Fig. 12.6a). An absorbable suture is secured in the anterior tendon fibers, which are then detached from the sclera at the insertion (>Fig. 12.6a). The detached portion of the tendon is then advanced temporally and sutured to the sclera 8 mm posterior and 2 mm superior to the superior edge of the lateral rectus muscle insertion (>Fig. 12.6b). Passive incycloduction of the globe is usually obvious when the tendon is advanced (>Fig. 12.7).

12.2  Superior-Oblique-Strengthening Procedures

12.2.2.1 Using Adjustable Sutures If the potential to adjust the final position of the new tendon insertion is desired, the suture can be tied in a temporary knot [12]. After the desired alignment has been achieved through postoperative adjustment, a permanent knot is tied and the sutures cut (>Fig. 12.8). We often prefer intraoperative adjustment. Intraoperative adjustment is facilitated by viewing the fundus intraoperatively prior to beginning surgery, making

Fig. 12.7. Passive incycloduction of the globe is usually obvious when the tendon is advanced during a Harada-Ito procedure

Fig. 12.8. Adjustable Harada-Ito procedure

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Chapter 12 Fig. 12.9a,b. Intraoperative adjustment of Harada-Ito procedure based on degree of objective retinal torsion. a Indirect ophthalmoscope schematic of the fundus demonstrating the relationship of the fovea and optic nerve in an eye with excyclotorsion. b Normal relationship reestablished

Fig. 12.10a,b. Classic Harada-Ito procedure. A 5-0 Mersilene doublearmed suture is passed around the anterior portion of the superior oblique tendon. The needles are passed 8 mm posterior to the inser-

note of the degree of objective retinal torsion based upon the optic nerve–fovea relationship. In a normal eye, a horizontal line drawn from the fovea intersects with the lower half of the disc (>Fig. 12.9). The position of the new insertion of the anterior fibers of the superior oblique tendon is adjusted until a normal optic nerve–fovea relationship is established.

12.2.3 Technique for the Classic Harada-Ito Procedure The classic Harada-Ito procedure has the advantage of being more easily reversed than the Fells modification of this procedure. The anterior portion of the tendon is isolated as described for the Fells modification. A 5-0 Mersilene double-armed suture is passed around the anterior portion of the tendon. The needles are then passed 8 mm posterior to the insertion site of the lateral rectus muscle at its superior border. The suture is pulled forward bringing the anterior portion of the tendon toward the lateral rectus (>Fig. 12.10).

tion site of the lateral rectus at its superior border. The suture is pulled forward bringing the anterior portion of the tendon toward the lateral rectus muscle

12.3 Superior-ObliqueWeakening Procedures Indications for weakening procedures of the superior oblique muscle include treatment of superior oblique overaction, A-pattern strabismus, Brown syndrome, and incyclotorsion. Though the superior oblique muscle is a tertiary abductor (Chap. 2), the primary position horizontal effect of a weakening procedure on the superior oblique is considered to be negligible [13–15]. Techniques to weaken the superior oblique include both graded and nongraded procedures. Graded procedures include silicone expander insertion and recession of the superior oblique tendon. Nongraded techniques include tenotomy and tenectomy. Posterior tenectomy and Z-splitting of the superior oblique tendon combines some degree of both graded and nongraded weakening procedures. Z-splitting of the tendon is prone to development of scarring of the tendon to the superior rectus muscle and sclera which may result in unexpected alignment issues after surgery. Because of this risk and the availabil-

 

Fig. 12.11a–e. Superior oblique nasal tenotomy and tenectomy. a Exposure of the nasal intermuscular septum. b Visualization of the superior oblique tendon, c followed by a small incision through Tenon’s

12.3  Superior-Oblique-Weakening Procedures

fascia directly over the tendon. d The tendon is then isolated on two small muscle hooks and e transected (tenotomy), or a portion of the tendon is excised (tenectomy)

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ity of more reliable weakening procedures, most surgeons do not advocate use of the Z-splitting technique. The advantages of a graded weakening procedure include the ability to titrate surgical effect, ability to perform asymmetric bilateral surgery, the potential for reversibility and access to the operated tendon should further surgery be needed in the future.

12.3.1 Technique of Superior Oblique Tenotomy and Tenectomy A superior oblique tenotomy or tenectomy may be performed on the tendon either nasal or temporal to the superior rectus muscle. During isolation of the tendon, the surgeon should minimize disturbance of the fascial tissues surrounding the tendon, which will minimize the risk of scarring between the cut ends of the tendon and the sclera. A fornix incision for both a nasal and temporal superior oblique tenotomy/tenectomy can be made in the superotemporal quadrant. Once bare sclera is exposed, the superior rectus muscle is isolated on a large muscle hook. A small muscle hook is used to retract the conjunctiva and Tenon’s fascia nasally (>Fig. 12.11a). A Desmarres retractor is placed along the nasal border of the superior rectus muscle and retracted posteriorly. The superior oblique tendon can be visualized through

Chapter 12

its surrounding fascia as white fibers running perpendicular to the superior rectus muscle against the sclera (>Fig. 12.11b). Once the superior oblique tendon is visualized, a small incision is made through Tenon’s fascia directly over the tendon (>Fig. 12.11c). The tendon is then hooked with a small muscle hook and brought through the incision, followed by placement of a second small muscle hook (>Fig. 12.11d). The exposed tendon is then transected (tenotomy) or a portion of the tendon excised (tenectomy) (>Fig. 12.11e). The exaggerated forced traction test (Chap. 8) is repeated to confirm that the entire tendon has been cut. A superior oblique tenotomy/tenectomy can also be performed from the temporal side of the superior rectus muscle. The effect of a tenotomy or tenectomy of the superior oblique tendon is greater as the procedure is performed closer to the trochlea. Isolation of the tendon on the temporal side is easier compared to locating the tendon on the nasal side of the superior rectus muscle. Once the superior oblique tendon has been isolated on a muscle hook, temporal traction is placed on the tendon to expose as much of the nasal portion of the tendon as possible. Once the nasal portion of the tendon is adequately exposed, a tenotomy or tenectomy is performed (>Fig. 12.12).

12.3.2 Technique for Guarded Superior Oblique Tenotomy The superior oblique tendon is isolated and transected nasal to the superior rectus muscle. A nonabsorbable suture is placed between the cut ends of the tendon, providing a guarded weakening procedure, allowing retrieval of the cut end of the tendon if needed at a future date (>Fig. 12.13).

Fig. 12.12. Superior oblique temporal tenotomy and tenectomy. Traction is placed on the tendon to expose as much of the nasal portion of the tendon as possible and a tenotomy or tenectomy is performed temporal to the superior rectus muscle

Fig. 12.13. Guarded nasal superior oblique tenotomy. A suture is placed between the cut ends of the tendon

 

12.3  Superior-Oblique-Weakening Procedures

The technique for weakening the superior oblique muscle by placement of a silicone expander in the tendon was described by Wright [16]. The placement of an expander to lengthen the superior oblique tendon offers several potential advantages. A graded weakening procedure can be performed, the risk of creating an iatrogenic superior oblique palsy can be minimized, and the technique facilitates reoperation, if needed [16–19].

The superior oblique tendon is isolated nasal to the superior rectus muscle as previously described for a nasal tenotomy/tenectomy procedure. Disturbance of the fascial tissues surrounding the tendon should be minimized. Care should be taken to avoid excessive dissection of Tenon’s capsule overlying the tendon, as this may result in postoperative complications including restricted elevation of the globe, or acquired Brown syndrome [17]. Two double-armed 5-0 or 6-0 Mersilene sutures are placed in the tendon. The first suture is placed approximately 3 mm nasal to the border of the superior rectus muscle and the sec-

Fig. 12.14a–e. Superior oblique tendon silicone expander. a Tenon’s capsule overlying the nasal portion of the superior oblique tendon is incised and the tendon isolated on a muscle hook. b Two doublearmed 5-0 or 6-0 Mersilene sutures are placed in the tendon and

c the tendon between these two sutures is transected. d A silicone 240 retinal band is sutured between the cut ends of the tendon using a horizontal mattress technique. e Tenon’s capsule overlying the tendon and expander is closed with absorbable suture

12.3.3 Technique for Superior Oblique Tendon Expander

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ond suture is placed approximately 2 mm nasal to the initial suture (>Fig. 12.14a, b). The tendon is then transected between these two sutures (>Fig. 12.14c). A silicone retinal 240 band that has been cut to the desired length is sutured between the cut ends of the superior oblique tendon using a horizontal mattress technique (>Fig. 12.14d). Tenon’s capsule overlying the tendon and expander is then closed with absorbable suture (>Fig. 12.14e). Care should be taken to avoid excessive dissection of Tenon’s capsule overlying the tendon, as this may result in postoperative complications including restricted elevation of the globe, or acquired Brown syndrome [17]. The length of the silicone band used is determined by the amount of superior oblique overaction present (>Table 12.1). For Brown syndrome a length of 6 mm is used in most cases.

12.3.4 Technique for Superior Oblique Recession

Chapter 12 Table 12.1. Length of silicone tendon expander to use in treatment of superior oblique overaction Superior oblique overaction

Length of expander (mm)

+1

4

+2

5

+3

6

+4

7

“hang-back” for the desired recession (>Fig. 12.15b). The sutures are then tied and trimmed. Alternatively, a temporary knot can be tied to allow later adjustment.

12.3.5 Technique for Superior Oblique Posterior Tenotomy/Tenectomy

Superior oblique recession offers several potential advantages including allowing for graded weakening of superior oblique muscle function, the potential for postoperative adjustment, and potential reversibility [14, 20–22]. A recession of the superior oblique tendon is performed after the tendon is isolated temporal to the superior rectus muscle. A double-armed absorbable suture is secured in the tendon approximately 4 mm from its insertion into the sclera (>Fig. 12.15a). The tendon is then detached at its insertion and the sutures passed through the sclera at the insertion site and the tendon is allowed to

Posterior tenotomy/tenectomy of the superior oblique tendon is performed at its insertion site into the sclera. The procedure provides a predictable weakening of the function of the superior oblique muscle for the treatment of A-pattern strabismus, primarily weakening its depression and abduction functions [23]. The superior oblique tendon is isolated temporal to the superior rectus muscle at its insertion. The posterior 7/8ths of the insertion is detached and a small wedge of the posterior tendon excised (>Fig. 12.16).

Fig. 12.15a,b. Superior oblique tendon recession. a A double-armed absorbable suture is secured in the tendon approximately 4 mm from its insertion into the sclera and the tendon detached from the globe.

b The sutures are passed through the sclera at the insertion site and the tendon allowed to “hang-back” for the desired recession

 

References

Fig. 12.16. Posterior 7/8ths tenotomy of the superior oblique tendon

References 1.

Santiago AP, Rosenbaum AL (1997) Grave complications after superior oblique tenotomy or tenectomy for Brown syndrome. J AAPOS 1:8–15 2. McNeer KW (1972) Untoward effects of superior oblique tenotomy. Ann Ophthalmol 4:747–750 passim 3. Plager DA (1990) Traction testing in superior oblique palsy. J Pediatr Ophthalmol Strabismus 27:136–140 4. Plager DA (1992) Tendon laxity in superior oblique palsy. Ophthalmology 99:1032–1038 5. Sato M, Amano E, Okamoto Y, Ota Y, Hirai T (2005) Interexaminer differences in the traction test of the superior oblique tendon. Jpn J Ophthalmol 49:216–219 6. Saunders R, Tomlinson E (1985) Quantitated superior oblique tendon tuck in the treatment of superior oblique muscle palsy. Am Orthopt J 35:81–89 7. Saunders RA (1986) Treatment of superior oblique palsy with superior oblique tendon tuck and inferior oblique muscle myectomy. Ophthalmology 93:1023–1027 8. Morris RJ, Scott WE, Keech RV (1992) Superior oblique tuck surgery in the management of superior oblique palsies. J Pediatr Ophthalmol Strabismus 29:337–346; discussion 347–348 9. Helveston EM, Ellis FD (1983) Superior oblique tuck for superior oblique palsy. Aust J Ophthalmol 11:215–220 10. Fells P (1974) Management of paralytic strabismus. Br J Ophthalmol 58:255–265 11. Harada M, Ito Y (1964) Surgical correction of cyclotropia. Jpn J Ophthalmol 8:88–95 12. Metz HS, Lerner H (1981) The adjustable Harada-Ito procedure. Arch Ophthalmol 99:624–626

13. Jin YH, Sung KR, Kook MS (1999) The immediate effect of bilateral superior oblique tenotomy on primary position horizontal binocular alignment. Binocul Vis Strabismus Q 14:33–38 14. Drummond GT, Pearce WG, Astle WF (1990) Recession of the superior oblique tendon in A-pattern strabismus. Can J Ophthalmol 25:301–305 15. Pollard ZF (1978) Superior oblique tenectomy in a pattern strabismus. Ann Ophthalmol 10:211–215 16. Wright KW (1991) Superior oblique silicone expander for Brown syndrome and superior oblique overaction. J Pediatr Ophthalmol Strabismus 28:101–107 17. Pollard ZF, Greenberg MF (2000) Results and complications in 66 cases using a silicone tendon expander on overacting superior obliques with A-pattern anisotropias. Binocul Vis Strabismus Q 15:113–120 18. Stager DR Jr., Parks MM, Stager DR Sr., Pesheva M (1999) Longterm results of silicone expander for moderate and severe Brown syndrome (Brown syndrome “plus”). J AAPOS 3:328–332 19. Wright KW, Min BM, Park C (1992) Comparison of superior oblique tendon expander to superior oblique tenotomy for the management of superior oblique overaction and Brown syndrome. J Pediatr Ophthalmol Strabismus 29:92–97; discussion 98–99 20. Sood S, Simon JW, Zobal-Ratner J (2002) Asymmetric “hangback” superior oblique recession. J AAPOS 6:198–200 21. Astle WF, Cornock E, Drummond GT (1993) Recession of the superior oblique tendon for inferior oblique palsy and Brown’s syndrome. Can J Ophthalmol 28:207–212 22. Buckley EG, Flynn JT (1983) Superior oblique recession versus tenotomy: a comparison of surgical results. J Pediatr Ophthalmol Strabismus 20:112–117 23. Shin GS, Elliott RL, Rosenbaum AL (1996) Posterior superior oblique tenectomy at the scleral insertion for collapse of A-pattern strabismus. J Pediatr Ophthalmol Strabismus 33:211–218

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Chapter

13

13 The purpose of transposition procedures is often misunderstood. Transposition procedures have a limited, but specific and important role in the treatment of strabismus. Transposition procedures are used only in cases of muscle paralysis or severe paresis. Common indications for rectus muscle transposition surgery include treatment of sixth nerve palsy, including Duane syndrome with severe abduction limitation, and paralysis of any single rectus muscle that is innervated by the third cranial nerve. In general, when referring to transposition procedures, one is referring to rectus muscles transposition procedures and that is the primary focus of this chapter. Transposition of the superior oblique tendon, a procedure rarely performed for the treatment of a third nerve palsy, is also reviewed in this chapter. Though anterior transposition of the inferior oblique muscle can be used to treat paralysis of the inferior rectus muscle, it is primarily indicated for treatment of conditions not caused by muscle paralysis and this procedure is discussed separately in Chap. 11. Rectus muscle transposition procedures work best when the function of only one rectus muscle in the eye to be operated is severely compromised. Transposition procedures can still be effective if the function of one or more rectus muscles to be transposed is only mildly compromised, but are almost entirely ineffective if the transposed muscles themselves are severely weakened. Transposition procedures do not involve the entire rectus muscle, but rather involve only the anterior third of the muscle that is not restrained by the rectus muscle pulley system [1]. The posterior portion of transposed rectus muscles remains in a relatively unchanged position after transposition surgery. The goal of transposition surgery is primarily to realign the deviating eye, optimally to the primary position, and hopefully achieving single vision with or without the aid of prism spectacles after surgery. The results of transposition surgery are usually good, but never perfect. Despite obtaining single vision in the primary position, the field of single vision may be limited following transposition surgery. Patients should recognize prior to surgery that ductions produced in the direction of the paralyzed muscle will not usually improve significantly following surgery, and any improvement in ductions will be minimal. There are reports in the literature of mild to moderate improvement of ocular ductions following transposition surgery that has been augmented through the placement of posterior fixation sutures, though scientific validation of these claims has yet to be established [2, 3].

The mechanism by which a transposition procedure produces improvement in primary position eye alignment is controversial. Some surgeons believe that some of the “function” of the transposed muscles is transferred in the direction of the paralyzed muscle through resting tone of the transposed muscles or a change in vector forces of the transposed muscles. Others believe that the transposed muscles act primarily as a passive restraint to hold the operated eye in the primary position. Yet another theory suggests that the rectus muscle pulleys, particularly following a posterior fixation suture augmented muscle transposition, are diverted posteriorly in the direction of the transposition while translating the center of the globe [4]. It is likely that more than one mechanism combines to create the improvement in primary position alignment achieved with transposition procedure. The ocular alignment results of a transposition procedure can be enhanced by weakening the antagonist of the paralyzed muscle, either through recession or through injection of botulinum toxin. Weakening of the yoke muscle in the sound eye may, in some cases, result in better alignment and a larger field of single vision when combined with a transposition procedure. The surgeon should carefully plan all transposition procedures, recognizing that additional strabismus surgery may be warranted on the patient in the future. The risk of anterior segment ischemia is increased, particularly in susceptible patients, when more than two rectus muscles are operated simultaneously in close sequence in the same eye (Chap. 20). Techniques to preserve one or more anterior ciliary vessels may be warranted in selected patients. Additionally, several months should be allowed to elapse before additional muscles are operated in the same eye in patients who are susceptible to anterior segment ischemia, allowing time for revascularization and the development of collateral blood flow, thus decreasing, but not eliminating, the risk of anterior segment ischemia. The surgeon who plans today for possible surgery tomorrow is likely to be rewarded for this effort by availability of a greater variety of surgical options if reoperation is later required. A large number of transposition procedures have been described over the last century with varying degrees of logic and success. Several procedures of historical interest will be briefly discussed and techniques still in common use today will be reviewed in detail including full tendon transposition, augmented full tendon transposition as described by Foster [3], and Buckley [5], Hummelsheim-type procedures, augmented Hummelsheim-type procedures as described by Brooks and

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coworkers [6], the Jensen procedure, and superior oblique tendon transposition. Adjustable sutures can be used on many transposition procedures and are described in Chap. 14. Anterior transposition of the inferior oblique muscle is reviewed in Chap. 11 rather than here, because this procedure is not commonly indicated for treatment of muscle paralysis. Hummelsheim [7] is credited with describing the first transposition procedure for paralytic strabismus. He described a partial transposition procedure involving the lateral halves of the superior and inferior rectus muscles to treat long-standing lateral rectus muscle paralysis. In Hummelsheim’s procedure, the transposed muscle segments were sutured directly to the lateral rectus muscle near its insertion (>Fig. 13.1a). If a large esotropia was present, a resection of the lateral rectus muscle and/or recession of the medial rectus muscle was often required. The effect of Hummelsheim’s procedure was reportedly enhanced by transposing the nasal halves of the vertical rectus muscles rather than the temporal halves of these muscles [8] (>Fig. 13.1b). Wiener and Scheie [9] advocated transecting a paralyzed horizontal rectus muscle posteriorly, splitting the muscle longitudinally, and suturing the proximal cut end of each muscle to the superior and inferior muscles, respectively (>Fig. 13.1c). Schillinger [10] recommended transposing the entire insertion of the vertical rectus muscles to compensate for a paralyzed horizontal rectus muscle. Likewise, transposition of the entire horizontal rectus muscle insertions was proposed as a treatment for vertical rectus muscle paralysis by Knapp

Chapter 13

[11]. This discussion highlights but a few of the historical aspects of transposition surgery to treat rectus muscle paralysis. Many authors have reported a wide variety of procedures and techniques not discussed here. The most common transposition procedure used today is a full tendon transposition or a variation of this procedure (>Fig. 13.1d).

13.1 Surgical Exposure for Transposition Procedures Transposition procedures can be performed through a 180° limbal incision or through two fornix incisions in adjacent quadrants. The incisions are placed as shown in Fig. 13.2. Either approach is acceptable and often depends entirely upon the surgeon’s preference. Surgeons who prefer a limbal incision believe this approach improves exposure and indeed exposure is superior with a limbal incision. Those who favor a fornix incision feel that patients are more comfortable postoperatively following surgery using this approach and that the surgical exposure available through a fornix incision is sufficient to allow safe transposition surgery. There is evidence in an animal model that leaving the limbal conjunctiva undisturbed may play a role in reducing the risk of anterior segment ischemia [12] (Chap. 20).

Fig. 13.1a–d. Several variations of early transposition procedures. a Hummelsheim, b O’Connor, c Widner, and a common procedure used today, d full tendon transposition

 

13.2  Transposition Surgery Techniques

Fig. 13.2a,b. Conjunctival incision for full tendon transposition; a fornix incisions, and b limbal incision

13.2 Transposition Surgery Techniques 13.2.1 Technique for Full Tendon Transposition A full tendon transposition procedure is indicated when there is paralysis or severe paresis of a rectus muscle. The procedure is most commonly used for treatment of a lateral rectus paralysis. The two adjacent rectus muscles are transposed to a position next to the insertion of the paralyzed muscle. Many surgeons reattach the transposed muscles to the sclera so that they roughly follow the spiral of Tillaux. In this example, the technique for treating a right lateral rectus paralysis is demonstrated, though a similar procedure can be used to treat paralysis of any single rectus muscle. The intermuscular septum of the superior and inferior rectus muscles is generously dissected for approximately 10–12 mm posterior to

Fig. 13.3. Full tendon transposition of the superior and inferior rectus muscle insertions for treatment of a lateral rectus muscle paralysis

the insertion. These two muscles are then detached from their insertions on the globe and transposed to a position adjacent to the insertion of the lateral rectus muscle (>Fig. 13.3). Practically speaking, the temporal border of the transposed muscle insertion will be placed adjacent to the upper border of the lateral rectus muscle for the superior rectus muscle (inferior border for the inferior rectus muscle) while the nasal border will be positioned at or near the temporal edge of the muscle’s previous insertion.

13.2.2 Technique for Full Tendon Transposition with Posterior Fixation Suture Augmentation (Foster Procedure) Foster [3] reported a technique in 1997 which represented a significant advance in the treatment of paralytic strabismus. His modification, though simple, powerfully influences the impact of a transposition procedure on primary position ocular alignment and has been reported to improve ductions in the field of action of the paralyzed muscle [2, 3], although the claims of improved ductions have not been scientifically validated. After a full tendon transposition has been completed, nonabsorbable sutures are used to augment the procedure by redirecting the belly of the muscle toward the paralyzed muscle. Posterior fixation sutures are used to secure the transposed muscle bellies to the sclera adjacent to the borders of the paralyzed muscle 12–14 mm posterior to the limbus (>Fig. 13.4). Concurrent recession of the antagonist muscle in the paralyzed eye has been associated with large overcorrections [3], and may be contraindicated. Recession of the yoke muscle in the sound eye has been recommended as an adjunct procedure if satisfactory primary position alignment is not achieved with augmented full tendon transposition alone [3]. Critics of the procedure often cite the potential for perturbations of vertical alignment, a complication that we have rarely encountered.

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13.2.3 Technique for Full Tendon Transposition with Lateral Rectus Muscle Fixation

Chapter 13

the anterior ciliary vessel associated with the paralyzed muscle to minimize the risk of anterior segment ischemia.

13.2.4 Techniques for Vessel-Sparing Full Tendon or Near Full Tendon Transposition

Buckley [5] described an augmentation procedure that involved posterior fixation suture augmentation affected by suturing the belly of the transposed muscles directly to the belly of the paralyzed muscle. The sutures are placed proximally 8 mm posterior to the muscle insertion, redirecting the transposed muscle’s force vector in the direction of the paralyzed muscle (>Fig. 13.5). Caution should be used to avoid ligating

Patients who are susceptible to anterior segment ischemia (Chap. 20) may still be candidates for transposition surgery, though modifications may be warranted to preserve all or part

Fig. 13.4. Augmented full tendon transposition procedure described by Foster. The belly of each transposed muscle is sutured to the sclera adjacent to the borders of the paralyzed rectus muscle

Fig. 13.5. Augmented full tendon transposition procedure described by Buckley. The belly of each transposed muscle is sutured to belly of the paralyzed rectus muscle

Fig. 13.6a,b. Full tendon transposition after dissection and sparing of the anterior ciliary vessel. a Dissection of the vessels and b appearance after transposition

 

of the anterior segment circulation. Protection from anterior segment ischemia is afforded by procedures that avoid cutting the anterior ciliary arteries. Careful dissection and sparing of one or both anterior ciliary vessels associated with each vertical rectus muscle can be done prior to transposition of the muscles [13] (>Fig. 13.6). Many surgeons prefer microscope magnification for this procedure. Coats and coworkers [14] reported near full tendon transposition of rectus muscles involving repositioning of four-fifths of the transposed rectus muscles leaving the remaining muscle and its anterior ciliary vessels intact (>Fig. 13.7). Avoidance of the need for tedious dissection of the anterior ciliary vessels is an advantage of this technique.

13.2  Transposition Surgery Techniques

13.2.5 Technique for HummelsheimType Transposition Hummelsheim [7] described a procedure for treatment of a longstanding lateral rectus palsy in which the temporal halves of the superior and inferior rectus muscles were partially transposed to the lateral rectus muscle insertion. The transposed muscle insertions were sutured directly to the lateral rectus muscle near its insertion. Today, half tendon transpositions of adjacent rectus muscles to treat a rectus muscle paralysis are generally accomplished by suturing the transposed muscle segments directly to the sclera adjacent to the paralyzed muscle’s insertion. Though technically incorrect, this modified procedure is often referred to as a Hummelsheim procedure. Though originally described for treatment of a lateral rectus muscle paralysis, a similar procedure can be used to treat any isolated rectus muscle paralysis in an eye. The superior and inferior rectus muscles are split longitudinally taking care to ensure that at least one anterior ciliary vessel is spared in each muscle. One half of each of the superior and inferior rectus muscles is transposed and sutured to the sclera adjacent to the paralyzed muscle insertion using 6.0 polygalactin suture (>Fig. 13.8).

13.2.5.1 Augmentation of a HummelsheimType Procedure

Fig. 13.7. Transposition of four-fifths of the rectus muscles with sparing of one anterior ciliary vessel in each transposed muscle

Brooks and coworkers [6] described a simple procedure to augment the effect of a Hummelsheim-type transposition procedure. In this modification, a 5-mm resection of the transposed muscle segment is made prior to suturing the trans-

Fig. 13.8a,b. Hummelsheim-type half tendon transposition. a Adjacent rectus muscles are split into two longitudinal halves, and b sutured to the sclera adjacent to the paralyzed rectus muscle insertion

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sutured in position adjacent to the superior rectus muscle insertion following the spiral of Tillaux (>Fig. 13.10b). This modification is still referred to as a Knapp procedure by many people, through this characterization is technically incorrect. Whether the muscle is sutured as originally described by Knapp or along the spiral of Tillaux probably has little effect on the success of the procedure. Reoperation, however, is technically easier if the new muscle insertion is placed along the spiral of Tillaux.

13.2.7 Technique for the Jensen Procedure

Fig. 13.9. Augmented Hummelsheim-type procedure. A 5-mm resection of each transposed muscle segment is made prior to suturing them to the sclera adjacent to the borders of the paralyzed rectus muscle insertion

posed muscle segment to the sclera adjacent to the borders of the paralyzed rectus muscle insertion (>Fig. 13.9).

13.2.6 Technique for the Knapp Transposition Procedure Knapp [11] described a procedure for transposing a functioning medial and lateral rectus muscle to a position adjacent to and perpendicular with the superior rectus muscle insertion to treat patients with monocular elevator deficiency (>Fig. 13.10a). Today, the transposed muscle segments are more commonly

The Jensen procedure was reported in 1964 as a treatment for chronic lateral rectus muscle paralysis [15]. The Jensen technique involves manipulation of the muscle bellies of the superior, inferior and lateral rectus muscles so that adjacent halves of these rectus muscles are brought into contact with each other using a nonabsorbable suture. The muscles are not disinserted for this procedure. Although the Jensen procedure has been proposed to avoid the risk of anterior segment ischemia, the condition has been reported following the Jensen transposition procedure [16, 17], including one case in a 10-year-old child [16]. The procedure, as described by Jensen, includes a medial rectus muscle recession if the primary position deviation was greater than 25 prism diopters. Though originally described as a treatment for sixth nerve palsy, the procedure can be similarly performed to treat paralysis of any single rectus muscle in an eye, assuming good to excellent function of the adjacent rectus muscle. The procedure is still most commonly performed for lateral rectus muscle paralysis but has mostly been replaced by various full tendon and partial tendon transposition procedures. When performing a Jensen procedure for lateral rectus muscle paralysis, the lateral rectus, superior rectus, and inferior rectus muscles are isolated and the muscle capsule and intermuscular septum of each muscle dissected to exposed the muscle for 12–15 mm posterior to each muscle’s insertion. A

Fig. 13.10a,b. Knapp procedure for monocular elevator deficiency. a As originally described, and b modified

 

13.2  Transposition Surgery Techniques

Fig. 13.11a–c. Jensen procedure for lateral rectus paralysis. a The superior and inferior and lateral rectus muscles are split longitudinally into two equal halves. Note that one anterior ciliary vessel has been left undisturbed in the nasal half of each of the vertical rectus muscles.

b Adjacent muscle halves are gently brought into contact approximately 12 mm from the limbus with a nonabsorbable suture. c The medial rectus muscle is recessed, if needed

muscle hook is used to split each muscle longitudinally into two equal halves (>Fig. 13.11a). The surgeon should attempt to leave at least one anterior ciliary artery undisturbed in the portion of each of the vertical rectus muscles not being transposed. The course of the anterior ciliary vessels can be complex and irregular and the surgeon should carefully review their course along the orbital surface of the muscle before proceeding. Nonabsorbable suture, such as 5.0 Mersilene, is then looped around adjacent rectus muscle segments and gently tied to bring adjacent muscle halves in contact approximately 12 mm posterior to the limbus (>Fig. 13.11b). The transposed muscle segments should not be crushed during this process, as excessive tension on the suture can result in rupture or damage to the rectus muscles. The medial rectus muscle is then recessed if needed and adjustable sutures can be used if desired on the

medial rectus muscle. (>Fig. 13.11c). Simultaneous recession of the medial rectus muscle increases the risk of anterior segment ischemia. Botulinum toxin injection is sometimes used instead of medial rectus muscle recession.

13.2.7.1 Vessel-Sparing Modification of the Jensen Procedure Coats [18] described a modification of the Jensen procedure that allows the surgeon to spare all of the anterior ciliary vessels. Instead of looping the suture around the entire rectus muscle segments to be transposed, the suture is passed beneath the anterior ciliary vessels on the orbital surface of each muscle

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Chapter 13

segment (>Fig. 13.12). The procedure is otherwise unchanged from the previous description.

13.2.8 Technique for Superior Oblique Tendon Transposition

Fig. 13.12. Vessel-sparing modification of the Jensen procedure. To avoid crushing the anterior ciliary vessels, the suture is passed under the anterior ciliary vessels on the orbital surface of the rectus muscles. The procedure is otherwise identical to a standard Jensen procedure

Fig. 13.13a–c. Superior oblique tendon transposition. a The superior oblique tendon is isolated nasally and cut near the superior rectus muscle. b The tendon is sutured to the sclera above the medial rectus

Superior oblique tendon transposition was first reported by Peter in 1934 [19]. Indications for the procedure are infrequent. Superior oblique tendon transposition can be used to improve ocular alignment in patients with complete or near-complete third cranial nerve palsy, and is most useful as an adjunct to other, more effective, procedures. As a stand-alone procedure,

muscle insertion under tension with nonabsorbable suture. c The protruding anterior portion of the tendon is excised

 

References

Fig. 13.14a,b. Fracture of the trochlea, an option during superior oblique tendon transposition surgery. a A hemostat is placed into the trochlea and the trochlea fractured. b Completed procedure

superior oblique tendon transposition is minimally effective and a large primary position deviation always persists. The procedure can be carried out through a fornix or a limbal incision. If a fornix incision is used, it should be placed in the superonasal quadrant. The superior oblique tendon is isolated on the globe along its nasal aspect and transected near the superior rectus muscle (>Fig. 13.13a). The assistant surgeon rotates the eye nasally and superiorly well beyond the primary position. The tendon is sutured to the sclera above the medial rectus muscle insertion under tension, using nonabsorbable suture such as 5.0 or 6.0 Mercilene (>Fig. 13.13b). The protruding anterior portion of the superior oblique tendon is excised and discarded (>Fig. 13.13c). Some surgeons prefer to fracture the trochlea, believing that this step will enhance the effect of the transposition, though this claim is debatable. Prior to suturing the tendon to the sclera, a hemostat is placed in the superonasal orbit until it is engaged in the trochlea. The hemostat is moved temporally to fracture the trochlea (>Fig. 13.14). While technically simple to perform, this step can result in bleeding and/or damage to the superior oblique tendon. The procedure is otherwise unchanged.

4.

5.

6.

7.

8. 9. 10. 11. 12.

References 1.

2.

3.

Miller JM, Demer JL, Rosenbaum AL (1993) Effect of transposition surgery on rectus muscle paths by magnetic resonance imaging. Ophthalmology 100:475–487 Paysse EA, Brady McCreery KM, Ross A, Coats DK (2002) Use of augmented rectus muscle transposition surgery for complex strabismus. Ophthalmology 109:1309–1314 Foster RS (1997) Vertical muscle transposition augmented with lateral fixation. J AAPOS 1:20–30

13.

14.

15.

Clark RA, Demer JL (2002) Rectus extraocular muscle pulley displacement after surgical transposition and posterior fixation for treatment of paralytic strabismus. Am J Ophthalmol 133:119–128 Buckley EG (2004) Paralytic strabismus. In: Plager DA (ed) Strabismus surgery. Basic and advanced strategies. Oxford University Press, New York, pp 88–89 Brooks SE, Olitsky SE, de BRG (2000) Augmented Hummelsheim procedure for paralytic strabismus. J Pediatr Ophthalmol Strabismus 37:189–195; quiz 226–227 Hummelsheim E (1908–1909) Weitere erfahrungen mit partieller sehnenuberpflanzung an den augenmuskeln. Arch Augenheilkd 62:71 O’Conner R (1921) Transplantation of ocular muscles. Am J Ophthalmol 4:838 Wiener M, Scheie HG (1952) Surgery of the eye, 3rd edn. Grune and Stratton, New York Schillinger RJ (1959) A new type of tendon transplant operation for abducens paralysis. J Int Coll Surg 31:593 Knapp P (1969) The surgical treatment of double-elevator paralysis. Trans Am Ophthalmol Soc 67:304 Fishman PH, Repka MX, Green WR, D’Anna SA, Guyton DL (1990) A primate model of anterior segment ischemia after strabismus surgery. The role of the conjunctival circulation. Ophthalmology 97:456–461 McKeown CA, Lambert HM, Shore JW (1989) Preservation of the anterior ciliary vessels during extraocular muscle surgery. Ophthalmology 96:498–506 Coats DK, Brady-McCreery KM, Paysse EA (2001) Split rectus muscle modified Foster procedure for paralytic strabismus: a report of 5 cases. Binocul Vis Strabismus Q 16:281–284 Jensen CD (1964) Rectus muscle union: a new operation for paralysis of the rectus muscles. Trans Pac Coast Otoophthalmol Soc Annu Meet 45:359–387

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Transposition Procedures 16. Bleik JH, Cherfan GM (1995) Anterior segment ischemia after the Jensen procedure in a 10-year-old patient. Am J Ophthalmol 119:524–525 17. von Noorden GK (1976) Anterior segment ischemia following the Jensen procedure. Arch Ophthalmol 94:845–847

Chapter 13 18. Kushner BJ, Coats DK, Kodsi SR et al (2002) Grand rounds #68: a case of consecutive exotropia after recession of all four horizontal rectus muscles for the treatment of nystagmus. Binocul Vis Strabismus Q 17:304–311 19. Peter (1934) Am J Ophthalmol 17:297

Chapter

Adjustable Suture Techniques

14

14 Adjustable suture use in strabismus surgery affords the surgeon the opportunity to inspect the ocular alignment achieved after surgery in an alert patient and allows adjustment of the final position of one or more extraocular muscles without the need to return to the operating room. Surgeons who use adjustable sutures believe that their use, particularly in patients with complex strabismus, results in superior outcomes. Many adjustable suture techniques have been described, some allowing wide latitude in the further recessing or advancing of a muscle, and others allowing more limited adjustment potential. Some adjustable procedures are designed to require no postoperative manipulation if the alignment is satisfactory, while other techniques require additional manipulation of all patients postoperatively to secure the final position of the muscle. Though adjustable sutures are primarily utilized for rectus muscle recession and resections, they can also be used during rectus muscle transposition surgery [1] and during surgery on the oblique muscles [2, 3] (Chap. 12). The use of adjustable sutures for rectus muscle recession and resection surgery is described in this chapter. Small modifications are required when using adjustable sutures during other procedures. The decision to use adjustable sutures depends both on the complexity of the surgery and on surgeon preference. Some surgeons strongly believe that adjustable sutures offer a distinct advantage while other surgeons do not see a significant enough benefit to justify their use. There are no definitive studies in the literature that prove either belief. Adjustable sutures can be used in one form or another on patients of any age, though most surgeons typically offer adjustable strabismus surgery techniques only to adult patients. Surgeons who are willing to utilize adjustable sutures on younger patients usually use one of several techniques. Some surgeons examine children in the recovery room and re-administer sedatives or general anesthesia to facilitate adjustment. Others depend on preoperative patient selection, with consideration for adjustable sutures limited to cooperative children and parents who have a good rapport with the surgeon [4]. Releasable adjustable suture techniques that require minimal postoperative manipulation have been described and are useful for pediatric strabismus surgery [5, 6]. The indications for adjustable suture use vary markedly depending upon individual surgeon training, experience, and

preference. Some surgeons utilize adjustable suture techniques widely while others use them far more selectively, or not at all. One common, generally agreed indication is for rectus muscle surgery in the treatment of incomitant strabismus, such as a rectus muscle paresis or restriction. Thyroid-related ophthalmopathy is a good example. While many variations of adjustable surgery have been described, this chapter will concentrate primarily on a few selected techniques that can be applied universally. Adjustable suture techniques can be performed through a limbal or a fornix incision, depending upon the procedure planned and surgeon preference. There is no universal agreement on the optimal time to assess ocular alignment and perform the final manipulation of the muscle(s) after surgery. There are advantages and disadvantages to each recommendation, and the approach chosen depends upon the training and experience of the individual surgeon. Some surgeons prefer to make final adjustments in the operating room after performing surgery with sedation and topical anesthesia [7] (Chap. 6). Others carry out adjustment in the recovery room or in the office an hour or more after surgery [8], while still others prefer to routinely make adjustments one or more days following surgery [9]. In our experience, the longer the duration from surgery to adjustment, the more difficult the adjustment tends to be because of one or more of the following reasons including patient discomfort, conjunctival edema, bleeding with tissue manipulation, and adherence of the muscle to the sclera. Surgeons who prefer to make adjustments several days to a week after surgery may choose to place viscoelastic or antimetabolites on the surgical site intraoperatively to reduce the initial degree of adherence of the muscle to the sclera before adjustment [5, 10].

14.1 Modifications of the Surgical Site for Adjustable Sutures Modifications of the surgical site are helpful to simplify the process of postoperative adjustment and to improve patient comfort. Adjustable sutures can be used with either a fornix or a limbal conjunctival incision. The modifications described below are applicable to any adjustable suture technique.

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14.1.1 Surgical Site Modifications for Adjustable Sutures Through a Limbal Incision Two techniques are commonly used to facilitate adjustable strabismus surgery through a limbal incision. First, the conjunctiva may be recessed to the level of the original insertion to allow ready access to the adjustable suture (>Fig. 14.1a). Alternatively, the surgeon may leave one corner of the limbal incision open, deferring suture closure of this corner until after the adjustment has been made (>Fig. 14.1b).

14.1.2 Surgical Site Modifications for Adjustable Sutures Through a Fornix Incision A retraction suture can be placed near the distal edge of the muscle insertion prior to the end of the procedure (>Fig. 14.2a). Gentle traction on this suture postoperatively will expose the surgical site, simplifying the process of adjustment (>Fig. 14.2b). The traction suture is removed after adjustment. Alternatively, adjustment can take place on the conjunctival surface. The needle on one end of the muscle suture is removed. The muscle suture ends are then tied together and

Chapter 14

are passed through the conjunctiva using the remaining needle (>Fig. 14.3a). Adjustment can then be done without manipulating the conjunctiva. Upon completion of the adjustment procedure, the suture knot should be made to retract into the opening in the conjunctiva (>Fig. 14.3b, c). The suture tends to cause significant patient discomfort if it remains externalized.

14.1.3 Bucket Handle Globe Manipulation Suture Manipulation of the globe during muscle adjustment can be uncomfortable for patients, regardless of the surgical approach utilized. The patient may be unwilling or unable to move and/ or hold his/her eyes in the direction requested by the surgeon during the adjustment process because of pain and discomfort, making adjustment complex. The use of a bucket handle suture on the sclera anterior to the muscle insertion can greatly facilitate both the process of adjustment and patient comfort. To place a bucket handle suture, an absorbable suture is passed into the sclera anterior to the muscle stump and is tied into a loop (>Fig. 14.4a). The suture loop can be grasped with forceps by the assistant surgeon to manipulate the globe during the adjustment process after surgery (>Fig. 14.4b). The bucket handle suture is removed upon completion of the adjustment procedure.

Fig. 14.1a,b. Limbal incision modifications for adjustable sutures. a Conjunctival recession to muscle insertion, or b deferred suture closure of one corner of the conjunctival incision

 

14.1  Modifications of the Surgical Site

Fig. 14.2a,b. Fornix incision modifications for adjustment in the episcleral space. a A conjunctival retraction suture is placed on the edge of the muscle insertion distal to the incision. b Traction on this suture postoperatively will expose the surgical site for suture adjustment

Fig. 14.3a–c. Fornix incision modifications for adjustment on the conjunctival surface. a The two ends of the muscle suture are tied together, one needle is removed, and the remaining needle passed through the conjunctiva

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Fig. 14.3a–c. (continued) Fornix incision modifications for adjustment on the conjunctival surface. b Appearance at end of the procedure,

Chapter 14

prior to adjustment. c After adjustment, a permanent knot is tied and made to retract into the episcleral space

Fig. 14.4a,b. Bucket handle suture for globe manipulation during adjustment. a An absorbable suture is passed into the sclera anterior to the muscle stump and tied into a loop. b The globe can be manipulated with this suture during adjustment

 

14.2 Adjustable Suture Techniques 14.2.1 Technique for Bow-Type Adjustable Sutures The bow-type technique can be applied to a recessed or resected rectus muscle. In both cases, the muscle sutures are passed back through the original insertion. If a recession is performed, a hang-back technique is used (Chap. 9). After the muscle is placed in the desired position, the suture ends are tied into a half bow (>Fig. 14.5a). If adjustment is required, the bow is untied, the muscle position adjusted, and the bow retied (>Fig. 14.5b). This procedure is repeated until ocular alignment is satisfactory. The bow is then converted into a permanent knot (>Fig. 14.5c). Some surgeons tuck the sutures under the conjunctiva and externalize them postoperatively only if adjustment is needed [11]. If the sutures have been covered with conjunctiva and the alignment is satisfactory, no further manipulation is necessary, as the bow is secure enough to hold the muscle in position during healing. The surgeon must understand the construction of the bow to prevent premature conversion to a permanent knot, which makes further adjustment very difficult. Pulling on the loose end of the bow loop suture will open the bow (>Fig. 14.6a), while pulling on the suture loop itself will convert it to a permanent knot (>Fig. 14.6b).

14.2.2 Technique for Cinch Knot Adjustable Sutures The cinch knot technique is preferred by some surgeons, especially by those who perform adjustable suture techniques through a fornix incision. The sutures from a bow-type closure tend to become tangled and can be difficult to work with when trying to use the bow technique with a fornix incision and the use of the cinch knot technique avoids this problem. The muscle sutures are passed through the muscle stump whether performing a resection or a recession. For a recession, a hangback technique is used (Chap. 9). The sutures can be placed close together in the center of the muscle stump or spread out along the muscle stump (>Fig. 14.7a). If the latter approach is used, it is helpful to make the scleral tunnel exits of the two suture passes as close together as possible. After placement of the sutures, the needles are removed and the muscle is pulled anteriorly until it makes contact with the muscle stump. While the surgical assistant holds the muscle in this position, a second absorbable suture is tied around the muscle sutures. If a recession is planned, the cinch suture is placed around the muscle suture anterior to the muscle stump to produce an adjustable hang-back muscle recession (>Fig. 14.7b). If a resection has been performed, the cinch suture is placed against the muscle stump.

14.2  Adjustable Suture Techniques

Prior to the conclusion of surgery, it is advisable to place a conjunctival traction suture on the edge of the muscle stump distal to the fornix incision as described above, a step that greatly simplifies postoperative adjustment (>Fig. 14.2a). At the conclusion of the case, the conjunctiva is re-approximated and three key sutures should extend out of the conjunctival incision including the conjunctiva traction suture (not shown in this example), cinch knot suture, and the muscle suture (>Fig. 14.7c). Gentle traction on the conjunctiva traction suture postoperatively will result in excellent exposure of the surgical site. Adjustment is later accomplished by sliding the cinch suture in an anterior or posterior direction, as needed (>Fig. 14.7d). When the desired position of the muscle has been achieved, the muscle sutures are then tied securely over the cinch knot (>Fig. 14.7e). Both absorbable and nonabsorbable sutures can be used for the cinch knot. In general, we favor absorbable sutures having seen nonabsorbable sutures migrate through the conjunctiva postoperatively weeks to months after surgery in several patients.

14.2.3 Technique for Traction Knot Adjustable Sutures Saunders and O’Neil [12] described a technique utilizing friction created in the scleral tunnel passes by placing knots along the muscle sutures to hold the muscle in position postoperatively (>Fig. 14.8a). The free ends of the sutures are allowed to extend from the wound following this procedure. If ocular alignment is satisfactory following surgery, the free ends of the muscle sutures are cut anterior to the knots and no further manipulation is needed (>Fig. 14.8b). The knots provide sufficient friction to prevent the muscle from retracting further posteriorly. If alignment is not satisfactory, the muscle can be advanced by pulling it anteriorly and tying a knot in the muscle sutures (>Fig. 14.8c). If further recession is needed, the knots can be easily pulled through the sclera suture tunnels by grasping the sutures posteriorly (>Fig. 14.8d). A permanent knot is tied when optimal alignment has been achieved after adjustment.

14.2.4 Technique for Ripcord Adjustable Sutures Coats [5] described an adjustable suture technique that allows for a one-time, single-step programmed recession of a recessed or resected muscle. The procedure is recommended for patients in whom adjustment potential is deemed desirable, but in whom standard adjustable suture techniques are not considered feasible. The rationale for this approach is that the majority of adjustments performed do not exceed 2–3 mm [9]. There is enough flexibility in the ocular motor fusion system that approaching optimal alignment, rather than achieving optimal alignment, is usually sufficient in most patients. The procedure can be used for a recession or a resection.

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Fig. 14.5a–c. Bow type adjustable suture technique. a After determining desired placement of the muscle, a half bow knot is tied. b The knot is untied for adjustment, and c converted to a permanent knot when alignment is satisfactory

 

14.2  Adjustable Suture Techniques

Fig. 14.6a,b. a Pulling on loose end of suture loop opens the bow, while b pulling on the suture loop results in conversion to a permanent knot

Fig. 14.7a–e. Cinch knot adjustable suture technique. a Two options for suture placement in the muscle stump. b A cinch suture is placed around the muscle suture. c Appearance of the eye at the end of sur-

gery. d Adjustment is accomplished by sliding the cinch suture along the muscle sutures, as needed. e When the desired alignment has been achieved, the muscle sutures are tied securely over the cinch knot

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Fig. 14.8a–d. Traction knot adjustable suture technique. a A knot is placed along each muscle suture. The free ends of sutures extend from the wound postoperatively. b The sutures distal to the knots are cut

14.2.4.1 Recession Technique The needles of a double-arm absorbable suture are passed through the sclera at the desired recession position. Prior to permanently tying the muscle sutures together, the muscle is allowed to hang back 1–3 mm (>Fig. 14.9a). A suture, known as the ripcord suture, is passed under the muscle suture knot (>Fig. 14.9b). This is accomplished by loading the needle in the needle holder backwards, lifting the muscle suture knot off the sclera, and passing the needle and suture beneath the knot. The needle attached to the ripcord suture is then passed through the sclera anterior and lateral to the muscle insertion. When tied, this suture will place traction on the muscle suture and advance the muscle to the desired recession position (>Fig. 14.9c). If adjustment is needed postoperatively, the ripcord suture can be cut and removed, resulting in an additional programmed recession (>Fig. 14.9d). If ocular alignment is satisfactory, no manipulation of the ripcord suture is needed.

Chapter 14

if alignment is satisfactory; no other manipulation is needed. c The muscle can be advanced and a permanent knot tied, or d further recessed and a permanent knot tied

14.2.4.2 Resection Technique A similar ripcord procedure can be performed to allow a onestep programmed adjustment of a rectus muscle resection. After performing a standard resection, and prior to permanently tying the muscle suture ends into a knot, the muscle is allowed to retract 1–3 mm posterior to the insertion (>Fig. 14.10a). The ripcord suture is then placed as described above for a recession procedure (>Fig. 14.10b). If recession of the muscle is required postoperatively, the ripcord suture is removed and the muscle is allowed to recess as programmed (>Fig. 14.10c). If ocular alignment is satisfactory, no manipulation of the ripcord suture is needed.

 

14.2  Adjustable Suture Techniques

Fig. 14.9a–d. Ripcord adjustable suture technique for rectus muscle recession. a The muscle is allowed to hang back 1–3 mm prior to tying the muscle suture ends together. b A ripcord suture is passed under the muscle suture knot. c When tied, the muscle is advanced to

the desired recession position. d The ripcord suture can be removed if further recession is needed postoperatively. If ocular alignment is satisfactory, no manipulation of the ripcord suture is needed

Fig. 14.10a–c. Ripcord adjustable suture technique for rectus muscle resection. a After performing a standard resection, the muscle is allowed to retract 1–3 mm posterior to the insertion and the muscle suture ends tied into a knot. b The ripcord suture is then placed. c The

ripcord suture can be removed if less resection effect is needed postoperatively. If ocular alignment is satisfactory, no manipulation of the ripcord suture is needed

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References 1.

2.

3. 4. 5. 6.

Laby DM, Rosenbaum AL (1994) Adjustable vertical rectus muscle transposition surgery. J Pediatr Ophthalmol Strabismus 31:75–78 Goldenberg-Cohen N, Tarczy-Hornoch K, Klink DF, Guyton DL (2005) Postoperative adjustable surgery of the superior oblique tendon. Strabismus 13:5–10 Metz HS, Lerner H (1981) The adjustable Harada-Ito procedure. Arch Ophthalmol 99:624–626 Dawson E, Bentley C, Lee J (2001) Adjustable squint surgery in children. Strabismus 9:221–224 Coats DK (2001) Ripcord adjustable suture technique for use in strabismus surgery. Arch Ophthalmol 119:1364–1367 Hakim OM, El-Hag YG, Haikal MA (2005) Releasable adjustable suture technique for children. J AAPOS 9:386–390

Chapter 14 7.

Ohmi G, Hosohata J, Okada AA, Fujikado T, Tanahashi N, Uchida I (1999) Strabismus surgery using the intraoperative adjustable suture method under anesthesia with propofol. Jpn J Ophthalmol 43:522–525 8. Luff AJ, Morris RJ, Wainwright AC (1993) Day case management in adjustable suture squint surgery. Eye 7 ( Pt 5):694–696 9. Bacal DA, Hertle RW, Maguire MG (1999) Correlation of postoperative extraocular muscle suture adjustment with its immediate effect on the strabismic deviation. Binocul Vis Strabismus Q 14:277–284 10. Paris V, Saya H (1990) [The use of Healon in surgery with adjustable sutures for strabismus]. Bull Soc Belge Ophtalmol 239:37–41 11. Engel JM, Rousta ST (2004) Adjustable sutures in children using a modified technique. J AAPOS 8:243–248 12. Saunders RA, O’Neil JW (1992) Tying the knot. Is it always necessary? Arch Ophthalmol 110:1318–1321

Chapter

Special Procedures

15

15 Most of the procedures described in this textbook are standard procedures that are used on a routine basis by most strabismus surgeons. The list of surgical procedures that have been described for the treatment of strabismus and the variations that have been described for existing procedures is exhaustive and cannot be adequately covered in a single volume on strabismus surgery. This chapter reviews several procedures that are used infrequently but that are nevertheless important in the armamentarium of the strabismus surgeon. These procedures are generally more complex than standard strabismus surgery techniques and are typically only required to manage unusually complex strabismus and/or strabismus that has been refractory to traditional surgery.

15.1 Periosteal Flap Fixation of the Globe Surgical management of complex paralytic strabismus can be challenging and surgical results disappointing. Paralytic strabismus due to oculomotor palsy is particularly difficult to effectively treat. Successful mechanical fixation of the globe in the primary position has been reported with use of various allograft [1, 2] and autogenous materials [3, 4]. Goldberg and coworkers [5] recently reported the use of apically based autogenous periosteal flaps to tether the globe in a fixed position near the primary position. We have found this technique to be an effective means of realigning the eyes of patients with complex paralytic strabismus, especially strabismus due to third cranial nerve paralysis. It is less complex than many previously reported procedures proposed to mechanically fixate the globe and does not involve surgery elsewhere on the body to obtain graft material. The procedure is done in conjunction with an oculoplastic surgeon, unless the strabismus surgeon has experience with surgery in the posterior aspect of the orbit and with surgical manipulation of the periosteum. An apically based periosteal flap can be created from the medial, lateral, superior or inferior orbital walls (>Fig. 15.1a–c). The optimal approach for a medial periosteal flap is through a caruncular conjunctival incision. After making the initial incision, blunt dissection is used to expose the periosteum and malleable retractors used to achieve adequate surgical exposure. A no. 12 Bard Parker blade is used to incise the periosteum to create a flap with its base in the orbital apex. We have used flaps based at the orbital rim

occasionally with success as well. The incision is initiated as far posteriorly as possible and should be carried anteriorly to the orbital rim (>Fig. 15.2a). The flap should be generously wide. A periosteal elevator is used to separate the flap from the underlying bone and a 5-0 Mersilene suture is secured to the anterior edge of the flap (>Fig. 15.2b). The sclera anterior to the paralyzed rectus muscle is exposed by retracting the incision toward the limbus and bluntly dissecting the surrounding tissue. We typically pass the sutures through the sclera anterior to the paralyzed rectus muscle insertion (>Fig. 15.2c). Long scleral suture bites are recommended to reduce the risk of the sutures cheese-wiring out of the sclera when the sutures are tied. The globe is then rotated toward the periosteal flap, well beyond the primary position. While the assistant surgeon holds the eye in this position and retracts the surrounding tissues, the surgeon secures the periosteal flap to the sclera by tying the suture ends together. The highly stylized diagram demonstrating this step is for illustrative purposes only, and it should be recognized that the surgeon is not able to actually visualize the surgical site as the flap is secured into place on the sclera. In reality, the surgeon must secure the flap to the sclera by feel. Figure 15.3 shows an eye during this step of the procedure, clearly demonstrating that the surgeon has limited or no view of the surgical site during this step. The incision is then closed with interrupted absorbable suture. We have yet to produce a long-term overcorrection with this procedure in a patient with strabismus severe enough to warrant its use. Initial overcorrection is the surgical goal and an initial overcorrection of 20–25 prism diopters is not unreasonable. The effect of the periosteal flap will degrade over the first few days to weeks after surgery.

15.2 Recession and Periosteal Fixation of a Rectus Muscle A rectus muscle can still have significant residual ability to move the globe despite a large recession or even a free tenotomy. This residual function occurs because of secondary connections between the muscle and the globe through Tenon’s fascia and surrounding structures. Even procedures that involve removal of the entire visible anterior portion of a rectus muscle without reattachment to the globe can be associated with some residual muscle function.

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Fig. 15.1a–c. Possible periosteal flap locations: a Medial orbital wall, b lateral orbital wall, and c superior orbital wall

Fig. 15.2a–c. Periosteal flap procedure. a After exposure of the periosteum, malleable retractors are used to improve surgical exposure and a flap is created with a no. 12 Bard Parker blade. A periosteal elevator is used to separate the periosteum from the underlying bone. b A 5-0

Mersilene suture is secured into the anterior edge of the flap. c The flap is then sutured to the muscle insertion or, as in this example, to the sclera anterior to the muscle insertion

Fig. 15.3. When securing the periosteal flap to the sclera, the surgeon is not able to actually visualize the surgical site, and completes this step by feel

 

Recession and transfer of a rectus muscle insertion to the adjacent periosteum has a powerful weakening effect on the action of the muscle. In theory, such a procedure is reversible, though we have yet had the opportunity to reverse such a procedure. Other than removing a muscle entirely, a procedure that is irreversible, transfer of the rectus muscle insertion to the adjacent periosteum is probably the most efficient way to maximally weaken a rectus muscle. Indications for this procedure are uncommon, and generally involve the need to weaken the antagonist of a completely paralyzed rectus muscle. The procedure is most commonly performed, in our experience, on the lateral rectus muscle as a component in the treatment of a complete third nerve palsy or Duane syndrome. The procedure is optimally performed through a limbal incision because exposure through a fornix incision is not usually sufficient to safely accomplish surgery. The lateral rectus muscle insertion is isolated, hooked, and exposed as usual. It is then is secured with a 5.0 Mersilene suture and detached from the sclera at its insertion. Two techniques can be used to suture the muscle to the periosteum. This first involves blunt dissection to expose the periosteum followed by placement of the suture in the periosteal tissues under direct visualization. The second is passage of the suture through periorbital adipose tissues to reach the periosteum without actually exposing the periosteum. This is our preferred approach because of its simplicity. In order to successfully carry out this approach, a sturdy needle, such as an S-14 or S-24 needle, is required and the needle needs to be bent into a more acute angle with a hemostat prior to passing the suture through the periosteum. Additionally, a malleable retractor is recommended to protect the globe as retrieval of the suture from the periosteum is attempted. Figure 15.4 depicts the completed procedure.

Fig. 15.4. Transfer of a rectus muscle insertion to the periosteum of the adjacent orbital wall. Schematic of completed procedure

15.4  Marginal Tenotomy/Myotomy

15.3 Postoperative Traction Sutures In rare situations, the use of traction sutures to fixate the globe into a particular position for a short period of time after surgery can be utilized to aid in the management of complex strabismus. There are no specific indications for their use, rather the surgeon develops a gestalt as to when postoperative traction sutures may be helpful. An example of when a traction suture might be helpful is following the dissection of extensive adhesions from the inferior aspect of the globe to treat a hypotropia. The surgeon may wish to fixate the eye in upward gaze for several days to a week following surgery to reduce the risk of recurrent adhesions, which would result in rapid recurrence of the hypotropia. A sturdy double-arm suture, such as 5.0 or 6.0 Mersiline, is passed partial thickness through the sclera. Both arms of the suture are then passed through the conjunctival fornix and the adjacent periosteum. Finally, the sutures are externalized through the skin. The needles are then passed through a rubber bolster and tied over the bolster to fixate the eye into position (>Fig. 15.5). The suture are cut and removed several days to a week after surgery.

15.4 Marginal Tenotomy/Myotomy Marginal tenotomy/myotomy was introduced in the early 1900s as a more controlled means of treating strabismus than was available through the use of myectomy or tenotomy, which was popular at the time. Marginal tenotomy/myectomy is rarely performed today, with one exception being marginal myotomy of the inferior oblique muscle, a favored weakening procedure for mild inferior oblique overaction by some surgeons. Marginal tenotomy/myotomy has potential value in two other situations that are occasionally encountered. The first is when there is a need to further weaken an already maximally recessed rectus muscle. Because a hang-back recession (Chap. 9)

Fig. 15.5. Traction suture placed to temporarily maintain the eye in a fixed position after surgery, in this case upward gaze

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can allow the surgeon to safely and effectively perform very large recessions, this scenario rarely occurs. The second clinical situation has been in the late repair of a lost muscle that has become so contracted that it cannot be attached to the sclera at or anterior to the equator without producing a large primary position deviation and a duction limitation. In these unusual situations, we have sutured the lost muscle to the sclera at the equator of the globe and performed a marginal myotomy to mitigate these concerns. A marginal tenotomy/myotomy is simple to perform on a normal muscle that has not been previously operated on, yet the procedure is rarely indicated in this setting. On the other hand, marginal tenotomy/myotomy is very difficult to perform on a rectus muscle that has been recessed far from its original insertion, on a rectus muscle that is severely contracted, or that is otherwise difficult to surgically access. Exposure can be exceedingly difficult and muscle rupture due to excess traction, damage to a vortex vein, and other complications are possible. While many variations of marginal tenotomy/myotomy procedures have been proposed, we perform one simple technique using two overlapping incisions involving 75% of the muscle’s width. The incisions must overlap, because if any of the fibers remain intact longitudinally, there will be little or no effect from the procedure [6]. The descriptions and diagrams provided here are schematic in nature only. In reality, the actual performance of a marginal tenotomy/myectomy is difficult. The reason that the procedure is difficult is because, when indicated, surgical exposure is generally very poor and/or the muscle is extremely tight, both making it very difficult to safely perform this otherwise simple procedure. To reduce hemorrhage from the muscle, a hemostat is placed across the muscle in the area where the marginal tenotomy or myotomy is to be performed (>Fig. 15.6a). If a right angle hemostat is not available, it is acceptable to place the hemostat on the muscle in a diagonal orientation. The hemostat is left is placed for 30–60 s which results in crushing of the muscle and its associated vascular supply, reducing the risk of significant hemorrhage. Blunt-tipped scissors are used to perform the tenotomy/myotomy (>Fig. 15.6b). If the muscle is

particularly tight, the anterior tenotomy can be performed by cutting the muscle with a scalpel, using a muscle hook under the muscle insertion to protect the sclera (>Fig. 15.6c). Great care must be used with further manipulation the globe after the procedure has been completed, because the now structurally weakened rectus muscle can be easily ruptured. Later strabismus surgery on a muscle that has undergone marginal myotomy is complex and difficult due to scarring and adhesions and a relatively fragile remaining muscle. Therefore, the decision to perform this procedure should be made with caution.

Fig. 15.6a–c. Marginal tenotomy/myotomy. a A hemostat is placed across the muscle in the area where the tendon/muscle is to be incised and removed after 30–60 s and b two overlapping 75% tenotomies/

myotomies are performed. c A scalpel can be used to cut the tendon anteriorly, using a muscle hook under the muscle insertion to protect the sclera if the muscle is extremely tight

15.5 Treatment of Esotropia and Hypotropia Associated with High Axial Myopia Patients with high axial myopia sometimes develop an unusual, restrictive strabismus characterized by development of a progressive esotropia and hypotropia with limitation of abduction and elevation. The condition is sometimes referred to as the heavy eye syndrome. Affected patients typically have myopia in excess of 10 prism diopters, usually much greater. Onset is typically during or after the fourth decade of life. Though initially believed to be caused by paralysis of the lateral rectus muscle due to pressure on the lateral rectus muscle as it was compressed between the lateral orbital wall and the enlarged globe [7], evidence now suggests that it is due to a mechanical problem of a different sort. Krzizoh and coworkers [8] reported magnetic resonance imaging evidence of downward displacement of the lateral rectus muscle by an average of 3.4 mm in patients with this condition. Aoki and coworkers [9] also investigated the paths of extraocular muscles through the orbit in patients with acquired esotropia and high axial myopia using magnetic resonance imaging. They found not only a consistent tendency for the lateral rectus muscle path to be deviated inferiorly, but also for the superior rectus muscle path to be deviated nasally in comparison to control groups having high myopia without esotropia. Additionally, the posterior globe was consistently

 

Fig. 15.7a–d. Treatment of esotropia/hypotropia in a patient with high myopia. a Union of the muscle belly of the lateral rectus muscle and the temporal half of the superior rectus muscle using two nonabsorbable sutures placed approximately 12 mm and 16 mm posterior to the limbus. b Preoperative and c postoperative alignment of a patient who underwent this muscle union procedure. d Orbital neuroimaging of a different patient showing typical malposition of the rectus muscles in a patient with high myopia-related strabismus. (Figure 15.7d reprinted with permission from British Journal of Ophthalmology, volume 81, Krzizok TH, Kaufmann H, Traupe H, New approach in strabismus surgery in high myopia, pp 625–630, Copyright 2007 [11])

15.5  Treatment of the Heavy Eye Syndrome

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noted to have prolapsed superotemporally between the superior and lateral rectus muscles. Figure 15.7a shows the orbital magnetic resonance image of a patient with this condition. Finally, Venkatesh and coworkers [10] recently reported evidence of a mitochondrial myopathy in a female patient with acquired esotropic strabismus fixus related to high myopia, and suggested that the presence of a mitochondrial myopathy might contribute to development of the disorder. Standard surgical techniques of recession and resection are almost universally ineffective in correcting the strabismus in this condition. Krzizok and coworkers [11] recommended treatment options which appear to be highly effective. Recognizing that the path of the lateral rectus muscle was deviated inferiorly in affected patients, they performed surgery to fixate the lateral rectus muscle back in the physiologic horizontal meridian at the equator of the globe using a silicone loop or nonabsorbable suture as a retroequatorial myopexy (poster­ ior fixation suture) along the horizontal meridian. Using this procedure, they were able to achieve good primary position alignment with improvement of abduction and elevation in affected patients. We have also achieved excellent results by the utilization of nonabsorbable sutures to create a union between the muscle belly of the entire lateral rectus muscle and the temporal half of the superior rectus muscle (>Fig. 15.7b). The muscles are not detached from the globe for this procedure. Two nonabsorbable sutures are placed approximately 12 mm and 16 mm posterior to the limbus, respectively, to bring the muscle bellies of the superior and lateral rectus muscles in contact with each other in the superotemporal quadrant. This maneuver forces the posterior portion of the globe into the posterocentral orbit and results in immediate alignment of the globe on the operating table. Ductions are also noted to improve following surgery. Figure 15.7c and d demonstrates the preoperative and postoperative alignment of a patient who underwent this procedure.

15.6 Horizontal Transposition of the Vertical Rectus Muscles to Treat Isolated Ocular Torticollis/Torsion In most cases, a head tilt is caused by hypertropia or cyclotropia and responds well to standard surgical strengthening or weakening procedures on the cyclovertical muscles. Occasionally, an ocular head tilt occurs in the absence of cyclovertical strabismus. This situation may be seen in isolation or in association with congenital nystagmus. The basic concept of surgical treatment is to rotate the eyes in the direction of the head tilt, which will result in improvement or resolution of the abnormal head tilt. The procedure presumably produces a tilt in the patient’s subjective visual environment, prompting the patient to straighten the head to relieve the induced image tilt [12]. Though several techniques have been suggested to accomplish this goal, we prefer the technique reported by von Noorden and coworkers [13] using horizontal transposition of the vertical rectus muscles. A full tendon transposition is done on both eyes as shown in Fig. 15.8. If the patient has significant amblyopia in one eye, the procedure is required only on

Chapter 15

the fixating eye. While von Noorden and coworkers [13] predicted that the effect of surgery might diminish with time due to mechano-elastic properties of the orbit, this has not been our experience.

15.7 Posterior Fixation Suture (Retroequatorial Myopexy, Fadenoperation) Cuppers [14] first described the posterior fixation suture technique to treat incomitant strabismus. The procedure has also been referred to as the “fadenoperation.” The term faden is the German word for suture or string. Therefore, it is incorrect to describe this procedure as a “faden suture.” The use of a posterior fixation suture may be employed in the treatment of incomitant strabismus in a variety of settings. It has also been used in the treatment of esotropia with a high accommodative convergence to accommodation (AC/A) ratio as well as dissociated vertical deviation. The mechanism of action of the posterior fixation suture procedure that has historically been taught is that the procedure shifts the effective insertion site of the rectus muscle posteriorly. According to this theory, this shift in the muscle’s insertion site reduces the effectiveness of muscle contraction on movement of the globe. Recently, this mechanism has been challenged. Clark and co-workers [15] quantified duction in the field of action following posterior fixation suture placement in a series of patients. The patients then underwent magnetic resonance imaging to verify anatomic changes. They also performed computed tomography in a cadaver containing radiographic markers to determine the effect of posterior fixation suture placement on the position of the medial rectus muscle insertion relative to its pulley. The results of their study indicated that posterior fixation sutures do not significantly reduce muscle torque during contraction. They found that posterior fixation sutures posteriorly displaced the pulley sleeve during contraction of the muscle resulting in a mechanical restriction after surgery accounting for limitation of ductions seen after the procedure. Posterior fixation sutures have been used in the treatment of esotropia with a high AC/A, though there is not universal approval of their use for this purpose. Kushner and co-workers [16] compared the use of the medial rectus muscle recessions combined with posterior fixation suture to standard medial rectus muscle recessions augmented to target the near angle in patients with a high AC/A. They found that a higher percentage of patients in the augmented recession group achieved satisfactory alignment and were able to discontinue wearing bifocals postoperatively compared to patients in the posterior fixation group. A 15-year follow-up of these patients continued to show that surgery for the near angle provided excellent motor and sensory results in these patients. Traditionally, a posterior fixation suture is used to suture a rectus muscle to the sclera using one or two nonabsorbable sutures 12–16 mm posterior to the limbus (>Fig. 15.9). The suture can be placed with or without prior recession of the muscle.

 

15.7  Posterior Fixation Suture

Fig. 15.8a,b. Full tendon horizontal transposition of the vertical rectus muscles to treat isolated ocular torticollis. a Transposition scheme for treatment of a right head tilt, and b for a left head tilt

Fig. 15.9. Posterior fixation suture technique. Schematic of completed procedure

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References 1.

2.

3. 4.

5.

6. 7.

8.

Wutthiphan S, Vajaradul Y, Lerdvitayasakul R, Nimvorapun T, Koochingchai W (2002) Ocular fixation with quadriceps tendon allograft. Cell Tissue Bank 3:121–126 Salazar-Leon JA, Ramirez-Ortiz MA, Salas-Vargas M (1998) The surgical correction of paralytic strabismus using fascia lata. J Pediatr Ophthalmol Strabismus 35:27–32 Scott AB, Miller JM, Collins CC (1992) Eye muscle prosthesis. J Pediatr Ophthalmol Strabismus 29:216–218 Bicas HE (1991) A surgically implanted elastic band to restore paralyzed ocular rotations. J Pediatr Ophthalmol Strabismus 28:10–13 Goldberg RA, Rosenbaum AL, Tong JT (2000) Use of apically based periosteal flaps as globe tethers in severe paretic strabismus. Arch Ophthalmol 118:431–437 Kroczek SE, Heyde EL, Helveston EM (1970) Quantifying the marginal myotomy. Am J Ophthalmol 70:204–209 Bagolini B, Tamburrelli C, Dickmann A, Colosimo C (1990) Convergent strabismus fixus in high myopic patients. Doc Ophthalmol 74:309–320 Krzizoh TH, Kaufmann H, Traupe H (1997) Elucidation of restrictive motility in high myopia by magnetic resonance imaging. Arch Ophthalmol 115:1019–1027

Chapter 15 9.

10.

11. 12.

13.

14.

15.

16.

Aoki Y, Nishida Y, Hayashi O et al (2003) Magnetic resonance imaging measurements of extraocular muscle path shift and posterior eyeball prolapse from the muscle cone in acquired esotropia with high myopia. Am J Ophthalmol 136:482–489 Venkatesh CP, Gayathri N, Murthy KR (2003) Myopic strabismus fixus: a mitochondrial myopathy? Am J Ophthalmol 135:720–722 Krzizok TH, Kaufmann H, Traupe H (1997) New approach in strabismus surgery in high myopia. Br J Ophthalmol 81:625–630 Conrad HG, de Decker W (1978) Rotatorischer Kestenbaum – Umalgerungshirurgie bei Kopfzwangshaltungen sur Schulter. Klin Monatsbl Augenkeilkd 173:681–690 von Noorden GK, Jenkins RH, Rosenbaum AL (1993) Horizontal transposition of the vertical rectus muscles for treatment of ocular torticollis. J Pediatr Ophthalmol Strabismus 30:8–14 Cuppers C (1976) The so-called “fadenoperation.” In Fells P (ed) Second Congress of the International Strabismological Association, p 395. Marseilles, Diffusion Generale de Librairie, France Clark RA, Isenberg SJ, Rosenbaum AL, Demer JL (1999) Posterior fixation sutures: a revised mechanical explanation for the fadenoperation based on rectus extraocular muscle pulleys. Am J Ophthalmol 128:702–714 Kushner BJ, Preslan MW, Morton GV (1987) Treatment of partly accommodative esotropia with a high accommodative convergence-accommodation ratio. Arch Ophthalmol 105:815–818

The Use of Botulinum Neurotoxin in the Treatment of Strabismus

Chapter

16

16 Historically, methods to improve ocular alignment have involved surgery on the extraocular muscles. The most frequently utilized procedure to weaken an extraocular muscle is a surgical recession. Surgical recession has traditionally been favored due to its predictability and long history of known favorable outcomes. In the late 1970s and early 1980s, Alan Scott pioneered the use of botulinum for weakening one or more extraocular muscles in the treatment of strabismus [1–3].

16.1 Mechanism of Action Botulinum is produced by the Gram-negative bacillus Clostri­ dium botulinum. It consists of several component proteins including both neurotoxic protein as well as associated nontoxic component proteins. Botulinum is initially produced as an inactive single chain molecule and becomes activated through a selective cleavage process yielding multiple protein chains. Seven different serotypes of botulinum toxin have been identified (A, B, C1, D, E, F, and G). Each of the serotypes is capable of producing a neurotoxic effect with a similar mechanism of action, but they differ in their relative potencies [4]. Type A botulinum toxin has been extensively studied and is the most commonly used serotype for the treatment of strabismus.

16.2 Effect on the Neuromuscular Junction The extraocular muscles are striated muscles and are innervated by motor neurons. The motor neurons that innervate the extraocular muscles originate in the midbrain and brainstem and travel to the orbit to directly innervate individual extraocular muscles. The motor neuron branches into terminals that contact several muscle fibers, each of which forms a neuromuscular synapse. A motor unit consists of several striated muscle fibers each of which is innervated by a single motor neuron. The motor neuron signals the muscle to contract via an action potential. When the action potential reaches the neuromuscular synapse, the terminal motor neuron depolarizes which subsequently stimulates the release of acetylcholine into the synaptic cleft. The release of acetylcholine into the synaptic cleft is a multistage process, which is in part controlled by several proteins known as SNAREs (soluble N-ethylmaleimide-sensi-

tive factor attachment protein receptors). SNAREs modulate the fusion of the acetylcholine vesicle to the cell membrane, which allows its release into the synaptic cleft. After its release, acetylcholine travels across the synaptic cleft to bind with nicotinic cholinergic receptors on the muscle fiber motor end-plate. This produces an action potential in the muscle fiber that then eventually leads to muscle contraction. Once injected, botulinum neurotoxin enters the presynaptic motor neuron through a process of endocytosis. This is a receptor-mediated process during which the toxin is completely encapsulated within a vesicle. Once inside the cell, the toxin molecule passes through the vesicle wall. The toxin molecule then cleaves one of the proteins that is responsible for fusion and release of the acetylcholine vesicle. The various botulinum toxin serotypes act upon different SNARE proteins.

16.3 Other Actions of Botulinum Neurotoxin Substance P is a neuropeptide that is involved in the genesis of pain. Like acetylcholine, substance P is released through a process requiring SNARE proteins. Botulinum has shown some clinical benefit in the relief of pain disorders mediated by substance P. Due to its large size, botulinum toxin is incapable of penetrating the blood–brain barrier. Therefore, direct effects of the neurotoxin on the central nervous system are not a concern.

16.4 History of Botulinum Neurotoxin in the Treatment of Strabismus In 1979, Alan Scott conducted an experiment on Rhesus monkeys in which he injected botulinum toxin into the horizontal rectus muscles. This initial research showed promise that botulinum toxin could be utilized to alter ocular realignment. Later experiments performed by Scott also showed efficacy of botulinum in the treatment of humans with strabismus. In these experiments, 42 patients with strabismus were injected with botulinum toxin [3]. The toxin was injected directly into extraocular muscles. The beneficial effect of the toxin injection lasted for a period of over 1 year in some patients. No systemic or local complications occurred. These encourag-

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ing reports in humans were the foundation for a later clinical trial in which 677 patients underwent treatment of strabismus with botulinum toxin. In 55% of the treated patients, ocular realignment had been achieved to within 10 prism diopters of orthotropia when evaluated at 6 months following initial injection. Botulinum toxin was approved by the U.S. Food and Drug Administration for the treatment of strabismus in 1989. Since its approval, many forms of strabismus have been treated with the toxin. In addition, the use of botulinum toxin has enjoyed a more widespread treatment spectrum including many nonstrabismic disorders, such as cervical dystonia, blepharospasm, and more recently cosmetic use for the treatment of facial wrinkles. The use of this agent in the treatment of medical conditions has spread across multiple disciplines.

16.5 Injection Techniques For botulinum toxin to achieve its desired effect, it must be directly injected into the belly of an extraocular muscle. This can be achieved in the operating room under direct visualization or through the use of electromyographic techniques, though some surgeons do not feel that electromyography use is critical to the success of the procedure [5]. When botulinum is injected at the same time that standard incisional strabismus surgery is being performed, the injection can be done under direct visualization. Generally, the conjunctiva is incised over the muscle and the agent is injected directly into the muscle belly. Botulinum toxin is commercially available under the trade name Botox® and is manufactured by Allergan. It is supplied in individual vials containing 100 units of freeze-dried toxin. Each unit contains approximately 0.25 ng of the protein. The toxin must be stored in a freezer until it is ready for use. Toxin is prepared for injection by reconstituting with nonpre-

Chapter 16

served normal saline. Reconstitution is based on the specific dilution required to achieve the desired concentration. Typically, for the treatment of strabismus, the desired concentration is 2.5 units/0.1 ml of solution. The package insert states that Botox® must be used within several hours of reconstitution to maintain its therapeutic affect. However, one study indicated that botulinum toxin maintains its potency if it is refrozen or refrigerated for up to 2 weeks, though the manufacturer does not recommend reusing stored Botox®. In a study by Sloop and co-workers [6], eight volunteers had freshly reconstituted Botox® injected into the extensor digitorum brevis. They then underwent repeat injections of Botox® which was either refrozen or refrigerated for 2 weeks. Muscle paralysis was measured by performing electromyography and comparing the degree of decline in M-wave amplitude after each injection. No difference was found between fresh, frozen, or refrigerated Botox®. However, a study in the otolaryngology literature performed by Gartlan and Hoffman [7] demonstrated a 70% loss in potency when Botox® was reconstituted, refrozen, and then assayed 2 weeks later. Currently most ophthalmologists attempt to use the majority of the reconstituted Botox® within several hours of its dilution. In clinical practice this often translates to multiple patients being treated with a single vial of toxin on the same day. Once the toxin is reconstituted, it is important to handle the vial carefully. Botulinum protein is delicate and is susceptible to destruction if the vial is shaken too aggressively. The diluted toxin is drawn into a tuberculin syringe using a disposable needle. A Teflon-coated needle is then placed on the syringe. The base of the needle is connected to a portable EMG machine. An EMG lead is attached to the patient’s forehead to complete the electrical circuit (>Fig. 16.1). After the conjunctiva is anesthetized with topical anesthetic, the needle is passed through the conjunctiva just posterior to the muscle insertion site on the sclera. While the needle is being passed into the orbit, the

Fig. 16.1. Injection of botulinum toxin using an EMG device. Diluted toxin is placed into a syringe with a Teflon-coated needle. The base of the needle is connected to a portable EMG machine. An EMG lead is attached to the patient’s forehead in order to complete the electrical circuit

 

patient is asked to look in the direction opposite the muscle to be injected. Stabilization of the eye with forceps as the needle penetrates the conjunctiva is often helpful. As the needle is advanced into the orbit, the ophthalmologist listens carefully for EMG evidence of needle entry into the muscle belly. Once the muscle belly has been penetrated, the patient is asked to look slowly toward the needle. An increase in the EMG signal verifies that the needle is indeed in the muscle. An alternative approach is to pass the needle between the orbital wall and the extraocular muscle to be treated. The needle is angled slightly toward the orbital wall. When the needle makes contact with orbital wall, it is redirected to enter the muscle belly (>Fig. 16.2). This technique can facilitate the use of botulinum by the less experienced ophthalmologist, by easing placement of the needle into the muscle and reducing the risk of globe perforation. Because the orbital wall has not been anesthetized, the patient may experience discomfort or pain when the needle touches the orbital wall. After the needle has entered the extraocular muscle, the botulinum is slowly injected. The sound emitted from the EMG recorder will be reduced as the injected fluid buffers contact between the needle and the muscle. The needle is then withdrawn from the orbit and topical antibiotics often administered before sending the patient home.

Fig. 16.2. Injection of botulinum toxin using the orbital wall for reference. The needle is directed toward the orbital wall until contact with bone is made, and then redirected into the muscle

16.6  Treatment of Strabismus with Botulinum Toxin

16.6 Treatment of Strabismus with Botulinum Toxin Following his initial human study, Scott performed additional studies using botulinum toxin in the treatment of strabismus. These studies continued to show a beneficial effect from botulinum toxin injection. Initial studies were conducted on adult patients with various forms of strabismus. No systemic or local complications occurred in these studies, except for the unwanted effect of the toxin on adjacent extraocular muscles [1, 2]. Later, Magoon and Scott [8] utilized botulinum toxin chemodenervation in infants and young children. In their study, 82 children 13 years of age or younger were injected with botulinum toxin for treatment of horizontal strabismus. All but one child achieved an improvement in ocular alignment. They were able to inject all children younger than 1 year of age and older than 6 years of age using only topical anesthesia and did not require sedation. Reinjection of botulinum toxin was required in 85% of the patients treated. Long-term follow-up of these same patients demonstrated stable ocular alignment over a 5-year period [9]. Later, in 1990, a larger study involving the use of botulinum in childhood strabismus was published by a group of strabismus surgeons. In this study, 413 children ranging in age from 2 months to 12 years were treated with botulinum toxin. Treatment averaged 1.7 injections per child with an average followup of 26 months after the last injection. Of the 362 patients who were available for follow-up, successful alignment, defined as correction to within 10 prism diopters of orthotropia, was achieved in 61% of the patients as a whole. The success rate varied depending on the condition being treated. Sixtysix percent of children with all forms of esotropia were successfully aligned compared with 65% of children with infantile esotropia, and 45% of children with exotropia. Patients with smaller deviations (10–20 prism diopters) were more likely to achieve successful alignment, with a success rate of 73%. In comparison, those with larger deviations (21–110 prism diopters) achieved success 54% of the time. No complications were reported in this study [10]. Early sensory data from children treated for infantile esotropia demonstrated results that compared unfavorably with historical data for standard incisional surgery. In a study by Ing [11] only 6 of 12 children demonstrated optimum motor alignment to within 10 prism diopters of orthotropia and only 3 of these patients demonstrated gross stereopsis. However, the sample size in Ing’s study was small and these results were considered preliminary. Further studies suggested that the motor results were comparable to incisional surgery. In 76 children ranging in age from 4 to 48 months, successful alignment was achieved in 68 (89%) children with esotropia. Forty achieved successful alignment with a single bilateral injection of Botox® and 36 required multiple bilateral injections to achieve successful alignment [12]. In a more uniform group of younger patients, Campos and coworkers [13] achieved successful alignment in 88% of children initially treated between the ages of 5 and 8 months with follow-up averaging 5 years. No variation of the angle of strabismus was observed after 6 months from the injection date. McNeer and coworkers [14] reported long-term

161

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sensory data on a group of 41 children treated with botulinum toxin prior to the age of 6 months. In this study, two-thirds of the children achieved some degree of stereopsis. Although the use of botulinum toxin in infantile esotropia has now been shown to be favorable in several studies, both from a motor and a sensory stand point, its use has not gained wide popularity. Reasons for this lack of popularity are uncertain, but several theories have been proposed. Most surgeons do not see an advantage to botulinum toxin injection if anesthesia or sedation is required for the procedure in younger patients. Additionally, side-effects such as ptosis, involvement of adjacent extraocular muscles, temporary exotropia and the need for more than one injection in many patients make the technique cumbersome and unsatisfactory for many patients, parents, and strabismus surgeons alike. Although serious complications have not been reported in previous studies, this may nevertheless be a concern to some strabismus surgeons, particularly those who are not experienced or comfortable with the technique. Finally, it may be that the historical tradition of a titrated medial rectus muscle recession and its well known risks and benefits is more familiar and more comfortable for the vast majority of surgeons treating infantile esotropia. While botulinum toxin has not been widely accepted by the strabismus surgical community for the treatment of young children with strabismus, it has achieved popularity among many ophthalmic surgeons for treatment of certain forms of strabismus in adults. It is most commonly used for the treatment of sensory strabismus and acute paralytic strabismus in the adult population. Metz and Dickey [15] treated 29 patients with acute unilateral sixth nerve palsy with botulinum toxin injection to the antagonist medial rectus muscle. Seventy-six percent of the patients had complete resolution of their sixth nerve palsy with follow-up Other authors also reported successful treatment in patients with sixth nerve palsy using botulinum toxin [16–18]. Theoretically, toxin injection into the antagonist medial rectus muscle during the acute stage of the palsy should prevent or reduce contracture of the medial rectus muscle and improve the chance of total recovery. However, a multicenter, nonrandomized study failed to demonstrate this [19]. In this multicenter study, 84 patients were enrolled by 46 different investigators. Sixty-two patients (74%) were treated conservatively and 22 patients (26%) were treated with botulinum injection. Recovery rates were similar between the two groups. Eighty-one percent of the patients managed conservatively and 83% of the patients treated with botulinum toxin recovered. Although botulinum toxin injections may not increase the recovery rates in patients with acute sixth nerve palsy, its use continues to be popular among some ophthalmologists. The use of botulinum toxin has also been reported for the treatment of fourth nerve and third nerve palsies, with variable success [20, 21]. Botulinum toxin injection is used in the treatment of comitant forms of strabismus in adults by some ophthalmologists. Dawson and coworkers [22] reported on their extensive experience with the use of botulinum toxin in patients with strabismus secondary to sensory deprivation. In their series, 503 patients were treated with botulinum toxin. Seventy-six percent of the patients had exotropia, 22.5% had esotropia, and 1.5% had a vertical strabismus. A total of 1457 injections were given,

Chapter 16

with a range of 1–50 injections per patient. Twenty percent of the patients continued to be managed successfully with toxin treatment, 43% eventually required surgery and 8% required no further treatment. Only 3% of their patients failed to obtain a reduction in their angle of deviation. The large number of re-treatments needed and the eventual need for surgery in a large proportion of patients may explain why most surgeons infrequently offer botulinum toxin injection to patients with strabismus. Another potential use for botulinum toxin has been for the treatment of small angle strabismus, including surgical underand overcorrections. Dawson and coworkers [23] injected 60 patients for the treatment of surgically overcorrected exotropia. The mean distance deviation was 17 prism diopters and the time from the last operation to botulinum toxin injection averaged 28 months. In the 36 patients with fusion potential, 15 achieved and maintained good ocular alignment with resolution of their diplopia following injection. In the 24 patients with poor fusion potential, only 4 patients achieved the same success. In a group of 68 patients with a small angle esotropia of less than 20 prism diopters, Dawson and Lee [24] performed a total of 434 injections, with an average of 6 injections per patient. Sixty-six percent of these patients underwent continued treatment and 19% achieved long-term benefit from a single injection. These studies demonstrated the potential benefits of botulinum toxin injection. However, the rate of success with a single injection is relatively low compared to conventional surgery. The convenience of in-office injection may be outweighed by the frequent need for multiple injections.

16.7 Botulinum Toxin in the Treatment of Nystagmus Adult patients with acquired nystagmus are generally bothered by both a reduction in visual acuity as well as oscillopsia. Botulinum toxin has been used in the treatment of acquired nystagmus. Crone and coworkers [25] first reported injecting botulinum toxin directly into the extraocular muscles for this purpose. Leigh and coworkers [26] also injected toxin directly into the muscles. In their report, two patients with multiplanar nystagmus underwent injection of the horizontal rectus muscles in one eye. Both patients demonstrated resolution of the horizontal component of their nystagmus as well as a small improvement in their visual acuity. Helveston and Pogrebniak [27] injected 25 units of botulinum toxin into the retrobulbar space of two patients. Both patients showed an improvement in their functional vision and one patient achieved an improvement in visual acuity from 20/80 to 20/30. The effect of the injection lasted from 5 to 13 weeks. Repka and coworkers [28] treated nine eyes of six patients with acquired nystagmus. They injected 25–30 units of botulinum toxin into the retrobulbar space. All patients demonstrated both subjective and objective improvement in their vision. Eye movement recordings showed a reduction of the amplitude of the nystagmus following the injection but the frequency was generally unchanged. The effect of the injection lasted no more than 8 weeks in most cases. We have found the use of retrobulbar botulinum toxin

 

to be helpful in these patients. Although it may induce strabismus, and occlusion of one eye may be needed, the reduction in nystagmus intensity achieved is often functionally beneficial.

16.8 Complications Serious complications associated with botulinum toxin injection are rare. Globe perforation with the risk of endophthalmitis or retinal detachment is uncommon in the hands of an experienced ophthalmologist. Liu and coworkers [29] reported a case of inadvertent intraocular injection of botulinum. Their patient did develop a retinal tear and retinal detachment though had a good visual outcome. The toxin itself did not appear harmful to the intraocular structures. Hoffman and coworkers [30] injected botulinum toxin into the vitreous of rabbit eyes and demonstrated no toxic affects to the retina. The most frequent side effect of botulinum toxin injection is unanticipated changes in alignment due to migration of the toxin to other extraocular muscles and the development of ptosis if the toxin migrates to the levator palpebrae superioris muscle of the upper eyelid. These potential side-effects are temporary and increase in frequency as the dose of toxin injected is increased [31]. We have had one patient treated with unilateral injection of 25 units of botulinum into the retrobulbar space to develop permanent horizontal diplopia, requiring the prescription of prism in her glasses.

References 1.

2.

3. 4.

5.

6.

7.

8.

9.

Scott AB (1980) Botulinum toxin injection into extraocular muscles as an alternative to strabismus surgery. J Pediatr Ophthalmol Strabismus 17:21–25 Scott AB (1980) Botulinum toxin injection into extraocular muscles as an alternative to strabismus surgery. Ophthalmology 87:1044–1049 Scott AB (1981) Botulinum toxin injection of eye muscles to correct strabismus. Trans Am Ophthalmol Soc 79:734–770 Aoki KR, Guyer B (2001) Botulinum toxin type A and other botulinum toxin serotypes: a comparative review of biochemical and pharmacological actions. Eur J Neurol 8 [Suppl 5]:21–29 Benabent EC, Garcia Hermosa P, Arrazola MT, Alio y Sanz JL (2002) Botulinum toxin injection without electromyographic assistance. J Pediatr Ophthalmol Strabismus 39:231–234 Sloop RR, Cole BA, Escutin RO (1997) Reconstituted botulinum toxin type A does not lose potency in humans if it is refrozen or refrigerated for 2 weeks before use. Neurology 48:249–253 Gartlan MG, Hoffman HT (1993) Crystalline preparation of botulinum toxin type A (Botox): degradation in potency with storage. Otolaryngol Head Neck Surg 108:135–140 Magoon E, Scott AB (1987) Botulinum toxin chemodenervation in infants and children: an alternative to incisional strabismus surgery. J Pediatr 110:719–722 Magoon EH (1989) Chemodenervation of strabismic children. A 2- to 5-year follow-up study compared with shorter follow-up. Ophthalmology 96:931–934

16.8  Complications 10. Scott AB, Magoon EH, McNeer KW, Stager DR (1990) Botulinum treatment of childhood strabismus. Ophthalmology 97:1434–1438 11. Ing MR (1993) Botulinum alignment for congenital esotropia. Ophthalmology 100:318–322 12. McNeer KW, Tucker MG, Spencer RF (1997) Botulinum toxin management of essential infantile esotropia in children. Arch Ophthalmol 115:1411–1418 13. Campos EC, Schiavi C, Bellusci C (2000) Critical age of botulinum toxin treatment in essential infantile esotropia. J Pediatr Ophthalmol Strabismus 37:328–332; quiz 354–355 14. McNeer KW, Tucker MG, Guerry CH, Spencer RF (2003) Incidence of stereopsis after treatment of infantile esotropia with botulinum toxin A. J Pediatr Ophthalmol Strabismus 40:288–292 15. Metz HS, Dickey CF (1991) Treatment of unilateral acute sixthnerve palsy with botulinum toxin. Am J Ophthalmol 112:381–384 16. Elston JS, Lee JP (1985) Paralytic strabismus: the role of botulinum toxin. Br J Ophthalmol 69:891–896 17. Wagner RS, Frohman LP (1989) Long-term results: botulinum for sixth nerve palsy. J Pediatr Ophthalmol Strabismus 26:106–108 18. Quah BL, Ling YL, Cheong PY, Balakrishnan V (1999) A review of 5 years’ experience in the use of botulinum toxin A in the treatment of sixth cranial nerve palsy at the Singapore National Eye Centre. Singapore Med J 40:405–409 19. Holmes JM, Beck RW, Kip KE, Droste PJ, Leske DA (2000) Botulinum toxin treatment versus conservative management in acute traumatic sixth nerve palsy or paresis. J AAPOS 4:145–149 20. Metz HS, Mazow M (1988) Botulinum toxin treatment of acute sixth and third nerve palsy. Graefes Arch Clin Exp Ophthalmol 226:141–144 21. Garnham L, Lawson JM, O’Neill D, Lee JP (1997) Botulinum toxin in fourth nerve palsies. Aust N Z J Ophthalmol 25:31–35 22. Dawson EL, Sainani A, Lee JP (2005) Does botulinum toxin have a role in the treatment of secondary strabismus? Strabismus 13:71–73 23. Dawson EL, Marshman WE, Lee JP (1999) Role of botulinum toxin A in surgically overcorrected exotropia. J AAPOS 3:269–271 24. Dawson EL, Lee JP (2004) Does Botulinum toxin have a role in the treatment of small-angle esotropia? Strabismus 12:257–260 25. Crone RA, de Jong PT, Notermans G (1984) [Treatment of nystagmus using injections of botulinum toxins into the eye muscles.] Klin Monatsbl Augenheilkd 184:216–217 26. Leigh RJ, Tomsak RL, Grant MP et al (1992) Effectiveness of bo­ tulinum toxin administered to abolish acquired nystagmus. Ann Neurol 32:633–642 27. Helveston EM, Pogrebniak AE (1988) Treatment of acquired nystagmus with botulinum A toxin. Am J Ophthalmol 106:584–586 28. Repka MX, Savino PJ, Reinecke RD (1994) Treatment of acquired nystagmus with botulinum neurotoxin A. Arch Ophthalmol 112:1320–1324 29. Liu M, Lee HC, Hertle RW, Ho AC (2004) Retinal detachment from inadvertent intraocular injection of botulinum toxin A. Am J Ophthalmol 137:201–202 30. Hoffman RO, Archer SM, Zirkelbach SL, Helveston EM (1987) The effect of intravitreal botulinum toxin on rabbit visual evoked potential. Ophthalmic Surg 18:118–119 31. Sener EC, Sanac AS (2000) Efficacy and complications of dose increments of botulinum toxin-A in the treatment of horizontal comitant strabismus. Eye 14:873–878

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Nonsurgical Treatment of Strabismus

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17 Not every disorder of ocular alignment requires treatment with surgery. Even practitioners with large surgical practices probably treat many more patients with strabismus using nonsurgical modalities than they do using surgical intervention. This chapter will review some of the most important nonsurgical treatment options for common forms of strabismus. For some conditions, surgery is rarely considered an option, while for others, surgery is often clearly the best treatment option. Before reviewing these issues in detail, it may be pertinent to briefly discuss the role of surgery in the strabismus patient. Many patients, and even some eye care professionals, erroneously regard surgery as a treatment of “last resort” for all patients with strabismus. Not only is this myth incorrect, it is also misleading and unfair to affected patients. In most cases where surgery is offered, far from being the “last resort,” it is often the optimal or only option to properly treat the disorder. Patients should understand that treatment is not based upon a step-wise protocol from the least invasive modality to most invasive modality. Rather, treatment recommendations are based on what the ophthalmologist feels is in the best interests of the patient overall. Although surgery may have more potential risks than other treatment options, it generally also has more potential benefit when offered. In many, if not most, cases where surgery is indicated, a decision to choose a nonsurgical treatment over a surgical one often means an outcome with fewer overall benefits. Although this does not mean that every patient should opt for surgical intervention when possible, it does suggest that patients should be aware of the alternatives and likely outcomes of treatment, both surgical and nonsurgical.

17.1 Spectacles 17.1.1 Accommodative Esotropia Spectacles are the mainstay of treatment for accommodative esotropia. Accommodative esotropia generally occurs in a child between 2 and 3 years of age, though it can be diagnosed at any age. Patients typically present with a history of an acquired intermittent or constant esotropia. The treatment of accommodative esotropia includes a prescription of the full

hyperopic correction as determined by cycloplegic refraction (>Fig. 17.1). There is no absolute rule as to how much hyperopia must be present to justify an attempt to correct a patient’s esotropia with spectacles. Most ophthalmologists will generally correct children who present with a new-onset esotropia with a hyperopic refractive error greater than +2.50 to +3.00 diopters. Spectacles may also be considered for smaller levels of hyperopia, especially when the esotropia is intermittent, significantly worse with near effort, and/or when it significantly worsens following cycloplegia. However, it is also useful to compare the esotropic deviation with the level of hyperopia before prescribing glasses. A very large deviation in the presence of a small to moderate amount of hyperopia is not likely to respond to spectacle correction, and a trial of spectacles is usually not warranted in such cases. Strabismus surgery is generally not indicated in patients who respond to their full hyperopic correction by re-establishing excellent ocular alignment. In an older child with a very small degree of hyperopia, surgery may be indicated to allow the child to maintain binocularity without the need for a pair of glasses that does not significantly improve visual acuity.

17.1.2 Poor Uncorrected Visual Acuity Spectacles are often useful in the treatment of strabismus in patients with poor uncorrected visual acuity. Patients with reduced vision due to uncorrected refractive errors may present with horizontal or vertical strabismus. Correction of the patient’s refractive error may improve vision resulting in an increase of “fusable” material in the patient’s visual space, which in turn can result in improvement of or control of the patient’s ocular motility disturbance. Correction of any significant refractive error, whether hyperopic, myopic, or astigmatic, can result in improvement of ocular alignment. Thus it is important to consider a trial of spectacle correction in all patients with poor vision and large uncorrected refractive errors prior to considering surgery. This scenario may be more common for patients with exotropia. The patient with an intermittent exotropia and a moderate to large degree of myopia may become aware of diplopia once their visual acuity is improved with a new prescription.

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Chapter 17

Fig. 17.1a,b. Accommodative esotropia. a Note eyes aligned with glasses, but b esotropia develops when glasses are removed

Once this occurs a greater effort will be made to fuse. We prescribe any significant level of myopic correction to patients with an intermittent exotropia and then reevaluate alignment once their new glasses have been worn for a period of time. Occasional patients with intermittent, or even constant, exotropia may be found to have a large degree of hyperopia on cycloplegic refraction. If the hyperopic refractive error is large, the patient may not exhibit the level of accommodative effort required to see clearly, and thus vision remains constantly blurred. Prescribing glasses to treat the hyperopic refractive error can improve visual acuity and may allow for better control of the deviation, much like that seen in patients with myopia [1]. However, we also warn parents that the reduced need to accommodate that results from correcting their hyperopia may result in worsening exotropia in some patients. In these cases it is important to maximize the visual acuity and treat the strabismus later, if necessary.

17.1.3 Over Minus Lens Therapy Over correcting minus lens therapy is used to stimulate accommodative convergence in patients with intermittent exotropia. Caltrider and Jampolsky [2] and Reynolds and co-workers [3] found that over minus lens therapy could be used to help improve fusional control in some patients with moderate angles of intermittent exotropia. However, in one study only 12% of patients treated in this manner were able to eventually discontinue use of their glasses. An important limitation of over minus lens therapy is accommodative asthenopia, restricting use of this treatment to young patients with large accommodative amplitudes. In addition, patients who do not require optical correction for improvement of their visual acuity are generally

less enthusiastic about this treatment and tend to be less compliant with this form of therapy.

17.1.4 Bifocal Lenses Many ophthalmologists correct accommodative esotropia with a high accommodative convergence to accommodation (AC/A) ratio with bifocals. Most ophthalmologists initially employ the use of +2.50 executive-type bifocal with the top of the lower segment intersecting the lower pupillary border, or titrate the bifocal to the minimum power that will allow the patient to achieve fusion at near. Although this is the most common form of treatment for accommodative esotropia with a high AC/A, other treatment options are available, including pharmacolo­ gic therapy with miotics, and strabismus surgery targeting the near deviation angle. Treatment of the distance deviation with single vision spectacles based on the cycloplegic refraction and observation of the near deviation may also be reasonable, as the high AC/A will often normalize with time [4, 5].

17.2 Occlusion Therapy 17.2.1 Part-Time Occlusion Part-time monocular occlusion therapy is used by some ophthalmologists in the treatment of intermittent exotropia. The objective of occlusion therapy is to eliminate the need for suppression which usually first begins to develop during the transition phase between an intermittent deviation and a constant

 

deviation. Occlusion is generally recommended late in the day when the deviation is most likely to be manifest. Occlusion during this time permits the deviation to occur (under the occlusive patch) while avoiding the need for active cortical suppression of the deviating eye to avoid diplopia. In a sense, this therapy can be thought of as a means to help the patient unlearn how to use suppression as an adaptive mechanism. This breakdown of the suppression mechanism may allow normal alignment and normal binocular vision during the remainder of the day. There are several small series reporting on the use of parttime occlusion in such patients. Freeman and Isenberg [6] reported on the use of part-time occlusion for early-onset exotropia. Eleven children with intermittent or constant exotropia were treated with part-time patching of the nondeviating eye from four to six hours a day. All patients initially demonstrated improved fusional control of their strabismus. After a mean follow-up of 22 months three patients (27%) became orthotropic and did not require further therapy. An equal number of patients later developed a constant exotropia and required strabismus surgery. This study suggests that part-time occlusion may postpone surgical intervention in some patients and possibly convert a small percentage of patients to orthotropia or exophoria, avoiding the need for surgery. Most ophthalmologists consider part-time occlusion therapy a temporizing measure which may allow improvement of the fusional control but which does not generally lead to tangible long-term benefits. It may be helpful in postponing surgery in some younger patients until they reach an age when amblyopia, disruption of stereopsis, or other problems following surgery are less likely to occur should an over correction take place.

17.2.2 Full-Time Occlusion Full-time occlusion is a reasonable treatment option in a small number of patients with chronic diplopia. Full-time occlusion of the nonfavored eye is an excellent option for the relief of diplopia in a selected minority of patients. For example, patients suffering from an acute cranial nerve palsy often benefit from occlusion of the nonfavored eye to eliminate diplopia while awaiting spontaneous recovery. Unfortunately, most patients will not tolerate full-time occlusion for an extended period of time. The visual discomfort, physical discomfort, and reduction of visual field associated with the use of an occlusive patch make this option viable for long-term treatment in relatively few patients. Full-time occlusion can also be used in the treatment of intractable diplopia either before or after strabismus surgery for nonparalytic strabismus. There are several methods available to occlude the visual axis for the relief of diplopia. The simplest method is the use of a patch. A patch can be either an adhesive patch or a tradition “pirate’s patch.” This form of occlusion allows for a simple placement and removal as desired by the patient. However, patients often consider this option cosmetically unacceptable and not usually a good option for use on a long-term basis. Occlusive material may also be placed on spectacle lenses and may

17.3  Orthoptic Therapy

consist of an opaque material or plastic tape. Bangerter foils are commercially available and can be used to degrade the visual acuity in one eye until bothersome diplopia is eliminated. A trial set of these foils may be used in the office to determine the foil that results in the least degradation of visual acuity, while eliminating bothersome diplopia. The foil is selected by the patient and placed on the spectacle lens of the nonfavored eye. Bangerter foils are less noticeable than traditional occlusive patches and are often better tolerated than standard patches. Contact lenses can be used in some patients who suffer from constant diplopia. The use of contact lenses is generally limited to patients who are able to properly handle and care for the contact lens as well as those patients without ophthalmic conditions in whom the use of a contact lens poses a significant risk, such as the patient with advance dry eye syndrome. A contact lens with an opaque center may be used to completely occlude the visual axis. Alternatively, the use of a high ­power plus contact lens may result in degradation of vision to the point that diplopia is no longer bothersome while allowing the patient to maintain use of their peripheral visual.. We have successfully used these therapies in patients for whom strabismus surgery was not felt to be a good treatment option.

17.3 Orthoptic Therapy Historically, orthoptic therapy has been used in the treatment of strabismus when surgical intervention has been thought to be too risky or unnecessary. However, with improvement in surgical techniques, improved safety of general anesthesia for young children and improved surgical outcomes, the role of orthoptic therapy has diminished with time. Currently, most ophthalmologists reserve orthoptic therapy for the treatment of intermittent exotropia where the angle of deviation is relatively small, perhaps 20 prism diopters or less. Even in these cases, orthoptic therapy often merely delays the need for surgery. Hiles and co-workers [7] reported on the long-term observation of 48 patients with intermittent exotropia who were followed for up to 22 years. Forty patients (83%) remained within 10 prism diopters of their original measurement by the end of the observation period. However, the study was retrospective and included selective instead of consecutive patients with intermittent exotropia. Their patients had either refused surgery or had fusional control that was thought to be too good to require surgical intervention. For most patients, orthoptic therapy consists of diplopia awareness training and improvement of fusional vergence amplitudes. Many patients with intermittent exotropia already experience diplopia consciously or subconsciously, as evidenced by their closing of one eye or the fact that the deviation is intermittent. In many patients with intermittent exotropia, fusional convergence amplitudes are already abnormally large. Therefore, many ophthalmologists limit the use of orthoptic therapy to increasing fusional convergence in patients with convergence insufficiency. In the past, orthoptic therapy was also used for the treatment of small angle esodeviations. Some esotropic patients who underwent diplopia awareness training as a child may

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Nonsurgical Treatment of Strabismus

Chapter 17

develop intractable diplopia later in life (Chap. 31). There are a few small series that report the successful use of orthoptic therapy in the treatment of vertical deviations [8]. Patients who have been treated successfully generally have small vertical deviations and their long-term prognosis is unknown.

17.4 Prism Correction Prism correction can be useful in the treatment of strabismus. It may be especially useful when used on a temporary basis or when treating a small angle deviation. Prism may also be useful when a small residual deviation remains following strabismus surgery. Patients who are most likely to respond favorably to prism therapy include patients with comitant, small angle strabismus. Patients who are currently wearing spectacle correction tend to accept prism therapy more readily than those who do not already wear spectacles. It is important to distinguish the difference between needing glasses to improve visual acuity and glasses used in the treatment of diplopia. Patients with a refractive error can often function quite well during many standard activities of daily living. In addition, intermittent squinting to create a pinhole effect allows for improve of visual acuity to a level that allows an excellent degree of function. Thus patients with small refractive errors may prefer not to wear glasses, as they can be quite functional without them. If not already wearing glasses, it is often difficult to convince a patient to succumb to them, even for correction of diplopia. Prescribed prism can be permanently placed into the spectacle lenses using offsets of the optical center of the glasses or by using ground in prism. A temporary press-on prism (i.e., Fresnel prisms) may be used as a temporary prism trial or as a good long-term option in some patients, especially those requiring large prism correction. A Fresnel prism is a series of smaller prisms of identical angle and identical power that are placed together on a membrane with no refractive power (>Fig. 17.2). These small prisms cover the entire surface of the lens and therefore all light will be refracted identically as though a simple prism was being used. However, a single prism of equal power would be much thicker and heavier than a Fresnel prism of like power. Fresnel prisms are made of flexible plastic and can be cut to fit either the concave or convex side of a spectacle. They can be placed horizontally, vertically, or obliquely. The advantage of Fresnel prisms is the ability to prescribe large prismatic correction without the extra weight and expense for comparable amounts of permanent spectacle prism. Furthermore, these prisms can be removed easily and they are therefore well suited for the temporary relief of diplopia. Although these properties of Fresnel prisms make them very useful tools in the treatment diplopia, other factors limit their usefulness in many cases. Fresnel prisms are subject to peeling off spectacles and to discoloration over time. Air bubbles often develop between the surface of the prism and the spectacle lens. Additionally, the use of a Fresnel prism typically

Fig. 17.2. Fresnel prism

results in a mild reduction of visual acuity and contrast sensitivity in the treated eye. While we most commonly use monocular occlusion to treat diplopia in patients with evolving cranial nerve palsies, we will occasionally prescribe a Fresnel prism for this purpose. They are not optimal for most patients in this setting, because of the marked incomitance that is typical of strabismus due to a cranial nerve palsy. When prescribed, the prism is placed on the spectacle lens of the nondominant eye. This tends to make the small decline in visual function associated with their use less bothersome to the patient. Patients who present with both a vertical and a horizontal deviation require special consideration. One option would be to prescribe a Fresnel prism for each spectacle lens, one for the horizontal deviation and one for the vertical deviation. This may lead to a bothersome reduction in visual function in both eyes, and is usually not well tolerated. A better option is usually to prescribe prism for the nondominant eye and place the prism obliquely on the spectacle lens to compensate for the bidirectional nature of the strabismus. In order to determine the power and direction of the prism to be used, the two vectors can be placed “head to tail” and the resultant vector (which represents the vector sum) will represent the single prism required to treat the deviation. The magnitude of this vector can be calculated using the Pythagorean theorem. The direction of the vector is determined by the formula: ArcTangent = (magnitude of vertical prism)/(magnitude of horizontal prism) The calculated prism can then be cut and placed on the lens surface in the direction needed. Alternatively, the power and vector of the prism can be determined utilizing a graphic approach. An example is demonstrated in Fig. 17.3. When small prism correction is needed long-term, we prefer the use of a permanent prism placed in the patient’s spectacle lenses. (Prentice’s rule for induced prism: PD = D · h, where PD

 

Fig. 17.3. Determination of the power and angle of an oblique prism. The horizontal and vertical prism are depicted using a vector format. The vectors are placed head to tail. In this example, a 6-PD base-in prism is combined with an 8-PD base-down prism. Using the Pytha­ gorean theorem, the magnitude of the oblique prism is calculated to be 10 PD. The angle of the direction of this prism is arc tan (x) = 8/6. Solving for x gives an approximate angle of 37°. Therefore, the new prism should be prescribed as 10 PD with the base down and in

is the power of the induced prism, D is the power of the lens in diopters, and h is the viewing distance from the optical center in cm.) Although occasional patients will tolerate the significant weight and image distortion that can occur with larger degrees of correction, we have found that most patient do not tolerate prism correction greater than 10 prism diopters. We are therefore unlikely to suggest this as a first line of treatment for deviations larger than 10 prism diopters. Prism can be placed into spectacles in one of two ways. Decentration of the optical center of the lens in accordance with Prentice’s rule can induce prism. To obtain a significant amount of prismatic effect, the patient must have a fairly large refractive error. Prism can also be ground into the spectacle lenses. The decision on how to best create prism in a patient’s spectacles is generally left up to the optician. However, we will specify the use of offset of the optical center of the lens in a small, select group of patients who have relatively small deviations that are incomitant. By offsetting the optical axis of the lens, not only are we able to induce the amount of required prism in the primary position but we are also able to take advantage of the change in prism power in eccentric gaze induced by this method to treat the incomitancy. Horizontal prism is usually split evenly between the two spectacle lenses, helping to distribute the weight of the spec-

References

tacles more evenly. However, when a relatively small degree of vertical prism is prescribed, it may be helpful to prescribe this as a base-up correction in only one eye whenever possible. By placing the prism in a base-up orientation, it avoids the problem of the thick prism base resting against the lower eyelid or the cheek, both of which patients find bothersome. Patients with vertical diplopia only in down gaze may benefit from prism correction in the form of a slab-off prism. This is prescribed in a similar manner to that required for patients who experience diplopia due to anisometropia after cataract surgery. Slab-off, or bicentric grinding, is a technique in which base-up prism is ground on half the lens in either the most minus or least plus lens. Unlike its use for anisometropia following cataract surgery, the purpose of bicentric grinding in patients with diplopia in down gaze is to induce a prismatic effect when looking down, not to reduce or eliminate it as in the patient with anisometropia. Regardless of which form of prism correction is used, it is important for the amount of prism correction needed to be precise, especially for vertical deviations. Small inaccuracies in the prism prescription can result in asthenopia or persistent diplopia. A Maddox rod may be helpful in measuring vertical deviations. A prism bar or Risley prism can be placed in front of one eye while holding the Maddox rod before the contralateral eye. The Maddox rod is placed in front of one eye in the vertical direction so that the patient sees a horizontal line when looking at a fixation light. The prism bar (or Risley prism) is then adjusted until the patient reports that the line from the Maddox bar runs directly through the fixation light. This method tends to be very accurate and reproducible. Nonsurgical modalities can and should be available in the treatment arsenal of the strabismus surgeon. Nonsurgical options can be helpful both for patients who do not need surgery and for those who do not want surgery. Nonsurgical measures can also be helpful for patients as a temporizing measure while awaiting surgery and can be invaluable for some patients to treat a small residual deviation after surgery. Some nonsurgical modalities may allow a surgeon to convert a less than ideal surgical outcome to one where the patient is satisfied and has comfortable single vision. While these nonsurgical treatment options are very important, the concept that surgery is a last resort option for the treatment of most instances of strabismus is a myth that should be ignored.

References 1.

2.

3.

Iacobucci IL, Archer SM, Giles CL (1993) Children with exotropia responsive to spectacle correction of hyperopia. Am J Ophthalmol 116:79–83 Caltrider N, Jampolsky A (1983) Overcorrecting minus lens therapy for treatment of intermittent exotropia. Ophthalmology 90:1160–1165 Reynolds J, Wackerhagen M, Olitsky SE (1994) Overminus lens therapy for intermittent exotropia. Am Orthopt J 44:86–91

169

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Nonsurgical Treatment of Strabismus 4. 5.

6.

Albert DG, Lederman ME (1973) Abnormal distance – near esotropia. Doc Ophthalmol 34:27–36 Pratt-Johnson JA, Tillson G (1985) The management of esotropia with high AC/A ratio (convergence excess). J Pediatr Ophthalmol Strabismus 22:238–242 Freeman RS, Isenberg SJ (1989) The use of part-time occlusion for early onset unilateral exotropia. J Pediatr Ophthalmol Strabismus 26:94–96

Chapter 17 7.

8.

Hiles DA, Davies GT, Costenbader FD (1968) Long-term observations on unoperated intermittent exotropia. Arch Ophthalmol 80:436–442 Cooper J (1988) Orthoptic treatment of vertical deviations. J Am Optom Assoc 59:463–468

Part II Complications of Strabismus Surgery

Chapter

Preoperative Management Errors

18

18 While successful implementation of surgical plans is critical in the successful management of a patient with strabismus, the first step to successful surgical care is preoperative management and good surgical decision-making. Errors in preoperative management can be divided into errors involving clinical judgment and errors involving technical or procedural errors. Many such errors can be avoided.

18.1 Errors in Preoperative Decision-Making 18.1.1 Field of Single Vision There is usually more than one reasonable surgical treatment plan that can satisfactorily treat most patients with strabismus, and no single technique or philosophy prevails for all patients and all situations. There are some conditions in which one treatment option may have significant advantages over other available plans. Errors in determining which eye and which muscle or muscles should be operated may be more likely in cases where restrictive, paralytic or incomitant strabismus is present. In these situations, alignment of the eyes in the primary position may offer a less than optimal solution. A surgical plan that will provide the largest reasonable field of single vision, in addition to improving primary position alignment, is optimal. Failure to consider the impact of the planned surgery on the field of single vision after surgery may result in a less than fully satisfied patient.

18.1.2 Monocular Diplopia Not every patient who presents with a complaint of double vision is found to have strabismus. Monocular diplopia may be the cause of symptoms in patients referred for evaluation of diplopia that is thought to be due to strabismus. Detection of monocular diplopia is important to avoid unnecessary ancillary testing and/or treatments, which will be ineffective in treating the patient’s symptoms. This is especially true when monocular diplopia occurs in a patient who also happens to have strabismus that is not producing symptoms. For example,

this may occur in a patient with a long-standing strabismus and suppression who develops a cataract which produces monocular diplopia. Strabismus surgery in such a patient will not provide relief from symptoms of diplopia. Most patients with binocular diplopia will quickly discover closing either eye can eliminate that double vision. Thus a reply that closure of one eye does not result in resolution of diplopia is usually the first clue that the patient has monocular diplopia. The patient who does not know if monocular eye closure eliminates their diplopia should be asked to close one eye to determine if the diplopia has resolved and then repeat the test with the second eye. This test must be performed for each eye, because the patient who has monocular diplopia in only one eye will report resolution of the diplopia with closure of the problem eye, a situation that can mimic binocular diplopia. The monocular nature of the diplopia, however, can be readily detected upon closure of the contralateral eye, when the patient will report that the diplopia persists. Common causes of monocular diplopia are listed in Table 18.1. In general, monocular Table 18.1. Causes of monocular diplopia Optical aberrations of the refractive media of the eye Uncorrected astigmatism Tear film disturbances Corneal disease

Corneal scarring Keratoconus

Lens disorders

Cataract Lens subluxation Intraocular lens issues (i.e., edge reflection, positioning holes) Following YAG capsulotomy

Iridectomy Macular distortion Monocular diplopia of cerebral origin (cerebral diplopia) [8]

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Preoperative Management Errors

diplopia that resolves when the patient looks through a pinhole is due to an abnormality anterior to the retina, while failure to resolve when viewing through a pinhole is usually a sign of a retinal etiology. Exceptions to this general rule exist. The cause of monocular diplopia can be determined in most cases with careful history and ophthalmologic examination. Referral to an anterior segment or retinal specialist is required in some cases for treatment, depending on the cause identified.

18.1.3 Nystagmus and Strabismus in Patients with a Compensatory Head Posture With small to moderate angle comitant strabismus, the strabismus surgeon may choose to operate on one or both eyes, and the effect of surgery is usually similar regardless of which eye(s) is operated. The choice between procedures that reduce or enhance the effect of muscle contraction on the globe is also, in most cases, up to the discretion of the operating surgeon. In patients with concurrent nystagmus, strabismus, and an abnormal head posture, the choice of procedures is not as simple and procedures are not necessarily interchangeable as in the examples above. The purpose of a compensatory head posture in a patient with nystagmus is generally to move the null zone, the place where the nystagmus intensity is reduced, to the frontal plane of the body to improve visual function. Surgical treatment is often warranted when an abnormal head posture produces symptoms of cervical discomfort, puts the patient at risk for developing facial asymmetry (Chap. 3), or is large and cosmetically unacceptable. Extraocular muscle surgery can reduce or even eliminate a compensatory head posture by rotating the null zone from an eccentric gaze position to the primary position. The basic surgical principle involves surgically moving the eyes in the direction of the abnormal head posture (Chap. 3). If the patient has straight eyes, surgery is performed on both eyes to produce symmetric movement of the eyes in the direction of the head posture. The surgical plan is not so straightforward for patients who have concurrent nystagmus and strabismus. In this setting, if surgery is to result in correction of the compensatory head posture, it must be performed on the eye preferred for fixation, and will have no effect if performed on the nonfixating eye. Thus, two major decisions must be made when planning surgery designed to simultaneously correct a compensatory head posture and strabismus. Surgery to correct the nystagmus is performed on the eye preferred for fixation while surgery to correct the strabismus is performed on the nonfixating eye, if needed. Surgery to correct the nystagmus should be planned first, as it may result in worsening of the patient’s strabismus. The surgical plan for strabismus repair is then devised after considering the impact of the nystagmus surgery on the strabismic deviation, which may improve or worsen depending on the individual circumstances. Both procedures can and should be carried out simultaneously, when indicated. An example of this is demonstrated in Fig. 18.1. The surgeon should not always assume that an abnormal head posture is compensatory solely in response to nystagmus.

Chapter 18

Incomitant strabismus can sometimes be responsible for all or part of the abnormal head posture. An abnormal head posture that is entirely the result of restrictive or paralytic strabismus is usually obvious. When the incomitant strabismus is responsible for only a fraction of the abnormal head posture, making this determination can be more difficult. Fortunately this situation arises infrequently.

18.1.4 Restrictive Strabismus If significant restriction of one or more extraocular muscles is present and contributing to the primary position ocular misalignment, failure to identify and address the restriction may result in a less than satisfactory outcome. Some cases may be obvious, such as strabismus due to thyroid orbitopathy. Others cases may not be so obvious. For example, a patient with a longstanding cranial nerve palsy may develop secondary contracture of the antagonist muscle, resulting in strabismus that has both a paralytic and restrictive component. If the restriction is not released, optimal alignment is unlikely, and the field of single vision may not be maximized. Forced duction testing in patients with a preoperative duction deficit is important, and is essential in helping to determine the cause of the duction deficit and in devising a treatment plan. Forced duction testing can be performed either in the examination room preoperatively or at the time of surgery in the operating room.

18.1.5 Paralytic Strabismus Like duction limitations that are due to restrictive strabismus, a muscle paresis or paralysis should be identified prior to surgery. Diagnosis is usually, but not always, relatively easy. Recognizing that the problem is due to a muscle weakness could not only lead to further systemic investigation, as appropriate, but can also facilitate optimal preoperative surgical planning. In general, such surgery includes operating on the antagonist muscle of the eye with the muscle paralysis. Various treatment schemes have been devised and are considered elsewhere. In cases of complete muscle paralysis involving a rectus muscle, a transposition procedure is often required, as resection of the antagonist muscle in the face of a total muscle paralysis will have little effect on the deviation and may greatly compromise future surgical options. In cases of paralytic strabismus, there exists a primary deviation, the deviation that is present when the nonparalytic eye is fixating, and a secondary deviation, which occurs when the paralytic eye becomes the fixating eye. The secondary deviation is always larger than the primary deviation due to Herring’s law of equal innervation (Chap 2). This issue is important when planning surgery on a patient with paralytic strabismus. If the patient prefers fixation with the paralytic eye, the larger, secondary deviation must be corrected, and this must be addressed in the surgical plan. A significant undercorrection is likely to occur in this setting if the secondary deviation is not addressed.

 

Fig. 18.1a,b. Surgery for a patient with concurrent strabismus, nystagmus, and a compensatory head posture. Preoperatively the patient had a left face turn and an esotropia with a right eye fixation preference. Surgery to move the null zone toward the primary position requires

18.1.6 Torsional Strabismus Torsional strabismus commonly occurs in association with vertical misalignment of the eyes, but may also occur in conjunction with horizontal strabismus. It occasionally presents in isolation. Failure to identify a significant torsional component of a strabismic deviation may lead to both an inaccurate diagnosis of the problem and a surgical plan that is inadequate to repair the problem. A classic example that we encounter most frequently is torsional strabismus in patients with bilateral superior oblique paresis. A concurrent V-pattern strabismus may be recognized and a small esotropia that occurs in down gaze, along with complaints of altered vision in the reading position, may lead the ophthalmologist to blame the small horizontal strabismus for the patient’s complaints. Patients may be prescribed reading glasses with prism in an effort to correct the

18.1  Errors in Preoperative Decision-Making

right lateral rectus recession with or without right medial rectus resection. This will have the secondary result of making the esotropia worse. A horizontal recess-resect operation to address this larger esotropia is required on the left eye, his nonfixating eye

esotropia. Worse, some patients may undergo horizontal strabismus surgery to correct the esotropia, a procedure which will provide no relief from torsion-related diplopia. However, careful questioning of the patient may elicit the true nature of the complaint, helping the surgeon to recognize that torsional strabismus is the problem. Tests for torsional strabismus, such as the double Maddox rod test, should be routinely used to detect torsional strabismus in patients with vertical strabismus and in patients with small angle strabismus who are unable to fuse with prism in place. Testing for torsion may also be of value in any patient who presents with diplopia in the presence of strabismus that does not adequately explain the patient’s symptoms. A fundus examination for evidence of objective torsion of the globe can also be of value, especially in children where subjective tests are difficult or impossible to perform.

175

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Preoperative Management Errors

18.1.7 Misdiagnosis of Apparent Duction Abnormalities 18.1.7.1 Apparent Duction Deficits While some abnormalities of ocular rotations are easy to overlook unless they are specifically considered, such as the aforementioned torsional strabismus, others may be easily seen but the findings misinterpreted. Patients with large angle esotropia may display a pseudo abduction deficit. This is classically seen in young children with large angle infantile esotropia. The presence of cross fixation may lead the observer to believe that an abduction deficit exists when it does not. If the patient has good vision in both eyes, an erroneous diagnosis of bilateral sixth nerve paresis may be made. When one eye is amblyopic, only the preferred eye may cross fixate and a unilateral palsy may be diagnosed. This erroneous diagnosis can lead to unnecessary neuroimaging and a mistaken belief that a transposition procedure is necessary to realign the eyes. A similar pattern may be seen in patients with a large angle exotropia in which an adduction deficit may appear to be present. Occluding one eye will often allow demonstration of normal ductions. Occlusion may be needed in some cases for a prolonged period of time to make this distinction.

Chapter 18

gradual development and increase of exotropia in cases of true inferior oblique overaction associated with a V-pattern. Pseudo inferior oblique overaction can also be seen following anterior transposition of the inferior oblique muscles [2]. This phenomenon has been labeled the anti-elevation syn­ drome and tends to occur when the lateral aspect of the transposed inferior oblique muscle is placed too anteriorly and/or when the new inferior oblique insertion is spread too widely (Chap 25). In such cases, there is limitation of elevation of the abducting eye due to restriction produced by the transposed inferior oblique muscle. This results in fixation duress of the restricted eye with “over elevation” of the adducting eye due to Hering’s law of equal innervation. Treatment involves revising the transposed inferior oblique insertion, moving it more posteriorly and/or narrowing the width of the transposed inferior oblique insertion. Capó and coworkers [3] described pseudo overaction of the superior and inferior oblique muscles in both eyes of patients with large angle exotropia (>Fig. 18.2). Upon correction of the exotropia alone, the oblique function returns to normal. They explained this phenomenon as occurring because of the shape of the orbits and demonstrate that, in a patient with exotropia, elevation of the abducting eye is checked sooner than elevation of the adducting eye by the shape and structure of the orbit (>Fig. 18.3). We have seen patients who have previously undergone weakening procedures of all four oblique muscles at the time of surgery for exotropia, when in reality only exotropia surgery was probably warranted.

18.1.7.2 Pseudo Oblique Overaction Pseudo inferior oblique overaction has been described by Kushner [1]. Patients with this relatively unusual motility disturbance appear to have over elevation of the adducting eye in the field of action of the inferior oblique muscles, often also demonstrating a Y-pattern with a large exotropia in up gaze. This has been suggested to represent a problem of co-innervation. Weakening of the inferior oblique muscles does not appear to offer any benefit. Differentiation from true inferior oblique overaction can often be made by noting the rapid development of exotropia in up gaze in these cases. This is in contrast to the

18.2 Errors in Measurements of Strabismus 18.2.1 Primary Position Measurement Errors Errors in the measurement of strabismus may occur due to mistakes made when positioning the patient for evaluation or in measuring the angle of deviation. The deviation angle should be measured in the primary position for all patients. Some patients will adopt a compensatory head posture in order to fuse.

Fig. 18.2a–d. Pseudo overaction of all four oblique muscles in a patient with exotropia

 

18.2  Errors in Measurements of Strabismus Fig. 18.3a,b. Mechanical explanation for pseudo oblique overaction. a Note symmetric upgaze when the eyes are aligned and b asymmetric checking of up gaze in exotropia due to orbital anatomy resulting in pseudo oblique overaction. {With permission from Capó H, Mallette RA, Guyton DL (1988) Overacting oblique muscles in exotropia: a mechanical explanation. J Pediatr Ophthalmol Strabismus 25:281–285 [3]}

bismus surgeons [4]. The examiner should be positioned directly in front of the prism to avoid parallax errors that can result in over or under estimation of the deviation. It is our opinion that the Hirschberg method of measuring strabismus is too inaccurate to be useful in the surgical management of most strabismus.

18.2.3 Prism Measurement Errors 18.2.3.1 Improper Prism Position

The ophthalmologist must be mindful of this strong tendency and deliberately straighten the patient’s head when performing preoperative measurements. Even a very small abnormal head posture can mask a large deviation. Unless the ophthalmologist is alert to this possibility, it can be easily overlooked and the patient’s primary position deviation underestimated or overlooked altogether. Measurements in other fields of gaze are often helpful and are often necessary when incomitant strabismus is present. Ideally, strabismus measurements in the nine positions of gaze should always be performed in a consistent gaze position. In routine practice, this is impractical, and in general, measurements are made in the most extreme positions of gaze possible. Patients with vertical strabismus should also be evaluated with their head tilted to either side in order to assist in the diagnosis of an isolated cyclovertical muscle palsy, if present.

18.2.2 Krimsky and Hirschberg Tests Alternate cover testing with prisms is the most accurate method of determining the angle of deviation in patients with strabismus. Some uncooperative patients, or patients with fixation too poor to allow alternate cover testing, may be measured with a modified Krimsky technique. However, it should be remembered that measurements made using the Krimsky ­ method may vary significantly, even when made by experienced stra-

Whether managing a child or an adult, diagnostic accuracy errors can and do occur. We prefer the term estimation of a patient’s deviation rather than measurement of a patient’s deviation for describing the process of strabismus quantification. This is because ocular alignment is a dynamic process and subject to change depending upon a variety factors including level of alertness, level of participation, gaze position, accommodative factors, and others. The frequency and degree of preoperative diagnostic accuracy errors can be reduced by recognition of several common problems. For example, the total deviation of a ray of light produced by a prism is the sum of the deviation produced at each surface of the prism. The total angle of deviation produced changes depending upon the orientation of the prism. The minimum angle of deviation is produced when a ray of light undergoes equal refraction at the two faces of a prism. Plastic prisms, the type generally used in ophthalmologic practice, are best held in the frontal plane position (>Fig. 18.4), a position that is easy to obtain and repeat and that will have an effect very close to the calibrated power of the prism. The total deviation induced by a prism changes as the angle of incidence of light striking a prism changes (>Fig. 18.5). Figure 18.6 presents a graph of the large degree of variation that can occur for various angles of incidence. Thus failure to properly orient a prism during quantification of strabismus can result in significant errors. Errors may be more likely to occur during measurement of deviations in eccentric positions of gaze, and even small errors in prism orientation can have important clinical effects when large prisms are used [5]. The apparent power of a prism also changes as the distance of the prism from the eye changes, with the apparent power of a prism becoming reduced as the distance of the prism from the eye is increased [6]. Thus the position of the prism relative to the corneal plane should be controlled and minimized.

177

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Preoperative Management Errors

Chapter 18 Fig. 18.4. Plastic prisms should be used in the frontal plane position

Fig. 18.5. Variation in the total angle of deviation created by changing the orientation of a prism relative to an incoming ray of light

18.2.3.2 Addition of Stacked Prisms Caution should be used when attempting to add prism powers together because the calibrated prism powers may not be arithmetically added by stacking two prisms together [6, 7]. A formula is available to calculate the prism power created by stacked prisms [6], but is cumbersome to use. A table that was developed by Thompson and Guyton [6] simplifies this process (>Table 18.2).

18.2.3.3 Addition of Prisms Held in Front of Both Eyes Strabismic angles measured in prism diopters are not additive. For small deviations, the error is clinically insignificant. Fortunately, it is only necessary to hold a prism in front of both eyes when a deviation is extremely large. When two large prisms are used to measure a deviation, a significant under estimation of the deviation will occur if the powers of the two prisms are simply added together. The measurements must be converted to degrees and then back into prism diopters. A table developed by Thompson and Guyton [6] simplifies this process (>Table 18.3).

18.2.4 Spectacle-Induced Measurement Errors 18.2.4.1 Large Refractive Errors The preoperative measurements on patients with large refractive errors who wear glasses during the measurements may also require adjustment [7]. The use of spectacles to correct high myopia introduces base-in prism for patients with esotropia and base-out prism for those with exotropia, increasing the apparent deviation for both conditions. Likewise, the use of spectacles to correct high hyperopia will reduce the measured deviation compared to the actual deviation present. These effects may become clinically important with spectacle correction of more than 5 diopters. In order to accurately determine the magnitude of the deviation, the patient may be measured with contact lens refractive correction, or the surgeon may calculate the true deviation after standard measurements while the patient is wearing spectacles. The formula to express the true deviation as a percentage of the measured deviation is as follows:

 

18.2  Errors in Measurements of Strabismus

179

Table 18.2. Deviation in prism diopters for addition of two stacked plastic prisms, with the posterior prism held in the frontal plane position. (Data from Ophthalmology, volume 90, Thompson JT, Guyton DL, Ophthalmic prisms. Measurement errors and how to minimize them, page 204–210, 1983, with permission from American Academy of Ophthalmology [6]) Added prism (labeled value in prism diopters)

Initial prism (labeled value in prism diopters) 10

12

14

16

18

20

25

30

35

40

45

50

1

11

13

15

17

19

21

27

32

37

43

48

54

2

12

14

16

18

20

23

28

33

39

45

50

56

3

13

15

17

19

22

24

29

35

40

46

52

58

4

14

16

18

21

23

25

30

36

42

48

54

61

5

15

17

20

22

24

26

32

38

44

50

56

63

6

16

19

21

23

25

27

33

39

45

52

59

66

7

17

20

22

24

26

29

35

41

47

54

61

68

8

19

21

23

25

28

30

36

42

49

56

63

71

9

20

22

24

27

29

31

37

44

51

58

66

74

10

21

23

25

28

30

33

39

46

53

60

68

77

12

23

25

28

30

33

35

42

49

57

65

74

84

14

25

28

30

33

35

38

45

53

61

70

80

91

16

28

30

33

36

38

41

49

57

66

76

87

100

18

30

33

35

38

41

44

52

61

71

82

95

110

20

33

35

38

41

44

47

56

66

76

89

104

122

25

39

42

45

49

52

56

66

78

93

110

133

165

30

46

49

53

57

61

66

78

94

114

141

183

264

35

53

57

61

66

71

76

93

114

144

195

315

-

40

60

65

70

76

82

89

110

141

195

339

-

-

45

68

74

80

87

95

104

133

183

315

-

-

-

50

77

84

91

100

110

122

165

265

-

-

-

-

Table 18.3. Deviation in prism diopters for addition of two prisms (glass or plastic) with one prism held in front of each eye. (Data from Ophthal­ mology, volume 90, Thompson JT, Guyton DL, Ophthalmic prisms. Measurement errors and how to minimize them, page 204–210, 1983, with permission from American Academy of Ophthalmology [9]) Left eye prism (labeled value) Right eye prism (labeled value) 10

12

14

16

18

20

25

30

35

40

45

50

10

20

22

24

26

29

31

36

41

47

52

58

63

12

22

24

26

29

31

33

38

44

49

55

60

66

14

24

26

29

31

33

35

40

46

52

57

63

69

16

26

29

31

33

35

37

43

48

54

60

66

72

18

29

31

33

35

37

39

45

51

57

63

69

75

20

31

33

35

37

39

42

47

53

59

65

71

78

25

36

38

40

43

45

47

53

59

66

72

79

86

30

41

44

46

48

51

53

59

66

73

80

87

94

35

47

49

52

54

57

59

66

73

80

87

95

103

40

52

55

57

60

63

65

72

80

87

95

104

113

45

58

60

63

66

69

71

79

87

95

104

113

123

50

63

66

69

72

75

78

86

94

103

113

123

133

180

Preoperative Management Errors

Chapter 18 Table 18.4. Representative examples of the impact of spectacle-induced artifact on measurement of strabismic deviations. {Data reprinted from American Journal of Ophthalmology, volume 96, Scattergood KD, Brown MH, and Guyton DL, Artifacts introduced by spectacle lenses in measurement of strabismic deviations, 439–448, Copyright (1983), with permission from Elsevier [7]} Spectacle lens power (diopters) –20 –10

Fig. 18.6. The deviation in prism diopters produced by a 40-prismdiopter plastic prism depending on the angle of incidence (degrees) when deviation is measured at a fixation distance of infinity. (Reprinted from Ophthalmology, volume 92, Thompson JT, Guyton DL, Ophthalmic prisms. Deviant behavior at near, page 684-690, 1985, with permission from American Academy of Ophthalmology [9])

True deviation as % of measured deviation

Change measured deviation by

67

Decrease by 33%

80

Decrease by 20%

Plano

100

No change

+10

133

Increase by 33%

+20

200

Increase by 100%

(Δt true deviation, Δm measured deviation, D diopters) [7]. Table 18.4 provides representative examples offered by Scattergood and coworkers [7] of the impact of various spectacle lens powers on the measurement of the true deviation. They suggest that mental interpolation between these points is usually sufficient for clinical purposes.

18.2.4.2 Unrecognized Prism Patients often do not know or recall that prism has been prescribed in their glasses. Routine assessment of spectacles in an ophthalmologist’s office may not detect the presence of prism (>Fig. 18.7). Undetected prism can lead to surgical undercorrection, which may go unrecognized until the patient obtains new glasses without prism following surgery. It is good practice to assess spectacles for the presence of induced prism prior to proceeding with strabismus surgery since identification of prism in the spectacles usually results in changes to the surgical plan. The portion of the spectacle lenses overlying the papillary axis should be marked prior to measuring the lens, and this mark centered in the lensometer when the lens reading is taken (>Fig. 18.8).

18.2.5 Duction Limitation Errors

Fig. 18.7a,b. Prism can easily go undetected in spectacles if a the optical center of the lens is centered in the lensometer, rather than b the portion of the lens overlying the pupillary axis

Patients with significant unilateral or asymmetric duction limitations can present interesting measurement issues, particularly when measurements are performed in the diagnostic positions of gaze. A significant duction limitation may prevent the patient from utilizing both eyes in the gaze position that the examiner is attempting to test. The patient may not recognize his/her role in the measurement process and may not realize that their inability to see the target with one eye represents a problem. This can result in marked underestimation of the

 

18.2  Errors in Measurements of Strabismus

Fig. 18.8. The portion of the lens overlying the papillary axis should be marked and this mark centered in the lensometer to detect induced prism in the patient’s spectacles

deviation. The ophthalmologist must be aware of this potential problem and ensure that the patient actually alternates fixation during alternate prism and cover testing. Though this sounds simple and intuitive, it can present quite a problem in some patients. If a duction limitation precludes accurate measurements in the desired position, two approaches can be utilized: (1) estimation of the deviation in the standard gaze position using the Krimsky light reflection test, or (2) measurement of the deviation in a reduced position of gaze that allows the patient to fixate the target with either eye.

18.2.6 Poor Fixation Patients, young and old, do not necessarily understand the objectives of alternate prism and cover testing. Patients often do not see the fixation target with one eye, and sometimes both eyes, and may not inform the ophthalmologist that the target is not seen, believing that the doctor knows what he/she is doing without their help. If the patient does not alter fixation during alternate cover prism and testing, so that the uncovered eye always takes up fixation on the visual target, the angle of strabismus can be dramatically underestimated. Causes of poor fixation in a child include both fear and lack of interest. Fixation issues can even be a problem in estimating strabismus in adult patients. To ensure that a patient routinely fixates on the visual target, the examiner can have the patient continue to read a string of letters thereby assuring continued fixation. When using larger prisms, those above 25–30 prism diopters, the image can be deviated so far toward the apex of the prism that it may not be possible for the patient to readily see the target even when they are trying to do so. When using large

Fig. 18.9a,b. Adjustment in the position of a large prism required to allow the patient to visualize the fixation target. a Patient unable to fixate target, and b patient able to fixate target after prism is moved to the right

prisms, we always ask whether the patient can see the target through the large prism, and adjust the position of the prism as needed until the patient can visualize the target before beginning testing (>Fig. 18.9).

18.2.7 Poor Cooperation Diagnosis of a patient with strabismus can be difficult, and sometimes a definitive diagnosis is not possible. Preoperative diagnostic inaccuracy should be included in the differential diagnosis when postoperative alignment is not as expected. For example, we recently treated a newborn who had what we believed to be congenital left sixth nerve palsy. The child fixated with the right eye and had amblyopia of the involved left eye. The child had an esotropia of 50 prism diopters and we could never demonstrate abduction past the midline in his left eye despite repeated attempts. After a period of observation and following conclusion of amblyopia treatment, surgery was recommended. The surgical plans called for a transposition of the superior and inferior rectus muscles to the lateral rectus

181

182

Preoperative Management Errors

muscle insertion with posterior fixation suture augmentation to treat his sixth nerve palsy. This would have been the plan carried out except that during the preoperative assessment 1 week before surgery the child’s mother mentioned that she had occasionally seen the left eye turn outward past the midline. With much effort, we did eventually demonstrate that the child had almost full abduction of the left eye, greatly altering our surgical plans. A recess/resect operation was performed with an excellent postoperative result. Such diagnostic errors do not reflect poor performance on the part of the ophthalmologist, but rather reflect the complexities and difficulties associated with evaluation and management of strabismus, especially in a young child. The most common problems to be misdiagnosed prior to surgery in our experience include sixth nerve palsy, Duane syndrome, and strabismus with an unrecognized accommodative component. In situations where we feel that patient cooperation significantly limits our ability to make an accurate diagnosis, we recommend deferring surgical intervention until the child is older and more cooperative.

18.3 Incomplete Diagnosis We once operated on a 4-year-old girl with a right superior oblique palsy who had marked right inferior oblique overaction and a left head tilt. A right inferior oblique recession was performed without complications. The patient returned 1 week later at which time her parents proclaimed that the surgery had been a complete failure and that her inferior oblique overaction and head tilt were completely unchanged. Compared with preoperative photographs and records, which demonstrated a left head tilt and right inferior oblique overaction, the patient now had a right head tilt and left inferior oblique overaction, prompting a diagnosis of bilateral superior oblique palsy that was not recognized prior to surgery. The patient underwent an inferior oblique muscle weakening procedure on the contralateral eye with good results. Obviously, it would have been better to diagnose the bilateral nature of the problem prior to surgery. Unlike an adult patient, where the nine diagnostic positions of gaze and head tilt test can be performed with good patient cooperation and usually with good accuracy, this is not always possible with a child, where surgical decisions must often be made based upon primary position measurements and evaluation of ductions alone. Undiagnosed Duane syndrome, accommodative esotropia, dissociated strabismus complex, and mild cranial neuropathies are also occasionally associated with unexpected postoperative alignment problems.

18.4 Management Errors at the Time of Surgery Once the patient has been properly examined, the strabismic deviation accurately measured and decisions regarding the surgical plan finalized, the basic plan should be understood

Chapter 18

by the patient and the surgeon must accurately carry out the plan, unless intraoperative findings call for an alteration of the original plans. The value of making sure that the patient understands the basic surgical plan and that the patient understands the possibility of an intraoperative change in plans cannot be overemphasized. It is much easier to explain a decision to perform an operation that may not be easily understood by the patient prior to surgery than attempting to do so after surgery. This is especially true if the outcome is less than what was anticipated. For example, many patients and/or families may not understand the recommendation to operate on both eyes when the patient has only “bad one,” the eye which the patient and family see deviating. An explanation in the examination room before surgery can usually resolve this confusion. This is best done prior to surgery and attempts to explain the decision about the surgical plan can be difficult after the surgery has been completed. Opinion varies as to the optimal time to obtain surgical consent. Some feel that it may be preferable for the operating surgeon to obtain surgical consent just prior to surgery, giving the patient the opportunity to have any remaining questions answered prior to surgery and it also helps reinforce to the surgical team which eye is to be operated and what procedure is to be performed. Others believe that it is optimal to obtain surgical consent in the more relaxed setting of the office days or weeks prior to surgery, followed by a brief review just prior to surgery.

18.4.1 Marking the Surgical Site Once the surgical consent has been obtained and the patient has been taken to the operating room, strict adherence to fundamental operating room safety protocols can help ensure that the procedure for which consent was obtained is the actual procedure that is performed and that the procedure is performed on the correct patient. Errors involving the performance of the wrong surgical procedure or at the wrong surgical site should, in theory, never occur. Errors in performing the consented procedure represent a breakdown in operating room protocol, and often involve errors at multiple steps in the process. Many hospitals require the surgeon to mark the operative site prior to the patient being brought into the operating room, especially when unilateral surgery is planned. Marking the surgical site should be done prior to taking the patient to the operating room after confirming the surgical site with the patient and/or parent, as appropriate, in the preoperative holding area. Even if this is not a requirement in a particular hospital, this safety precaution is easy to implement and provides reassurance to the patient and surgical team alike. When marking the surgical site, marking with an “X” is not recommended, but rather the surgeon’s initials should be utilized. This mark should be placed in an area that will still be visible after the surgical draping has been placed and the marking pen should contain ink that is resistant to removal during surgical preparation (Chap. 5). Additionally, some surgeons also prefer to mark the type of deviation (i.e., XT, ET,

 

etc.) for an added measure of safety. Prior to the first incision being made, a “timeout” should take place when the operating surgeon, anesthesiologist and other relevant operating room personnel all confirm that the surgical plan matches the operative consent, and the surgical team should confirm the identity of the patient through at least two patient identifiers (name, date of birth, and medical record number). This should be done even for patients who are undergoing surgery under local anesthesia. Unfailing and meticulous attention to these protocols, even when the site seems obvious or routine, can help to reduce the potential for a wrong site or wrong procedure error. Strabismus surgery, like all surgeries, has known associated risks. Some risks may be unavoidable even in the best of circumstances. With thoughtful and accurate preoperative management, the strabismus surgeon can help to minimize most of these risks and starting with an accurate surgical plan and surgical process of care are important first steps.

References

References 1. 2. 3.

4.

5.

6.

7.

8.

9.

Kushner BJ (1991) Pseudo inferior oblique overaction associated with Y and V patterns. Ophthalmology 98:1500–1505 Kushner BJ (1997) Restriction of elevation in abduction after inferior oblique anteriorization. J AAPOS 1:55–62 Capó H, Mallette RA, Guyton DL (1988) Overacting oblique muscles in exotropia: a mechanical explanation. J Pediatr Ophthalmol Strabismus 25:281–285 Choi RY, Kushner BJ (1998) The accuracy of experienced strabismologists using the Hirschberg and Krimsky tests. Ophthalmology 105:1301–1306 Repka MX, Arnoldi KA (1991) Lateral incomitance in exotropia: fact or artifact? J Pediatr Ophthalmol Strabismus 28:125–128; discussion 129–130 Thompson JT, Guyton DL (1983) Ophthalmic prisms. Measurement errors and how to minimize them. Ophthalmology 90:204–210 Scattergood KD, Brown MH, Guyton DL (1983) Artifacts introduced by spectacle lenses in the measurement of strabismic deviations. Am J Ophthalmol 96:439–448 Hirayama K, Satou M, Gotou H, Watanabe K, Yamamoto T (1995) [Cerebral diplopia and triplopia – a proposal for responsible lesion and mechanism.] Rinsho Shinkeigaku 35:744–750 Thompson JT, Guyton DL (1985) Ophthalmic prisms. Deviant behavior at near. Ophthalmology 92(5):684–690

183

Chapter

Anterior Segment and Ocular Surface Complications of Strabismus Surgery

19

19 Complications involving the anterior segment and ocular surface can vary from mild, inconvenient, and self-limiting to serious and vision threatening. This chapter will highlight common and uncommon problems that can be encountered during and after strabismus surgery and will review methods to both prevent complications and treat complications that do occur. The chapter is organized anatomically, with a section on corneal complications, conjunctival complications, scleral complications, and intraocular complications. Anterior segment ischemia is discussed separately in Chap. 20.

19.1 Corneal Complications Pedersen [1] reported corneal abnormalities in more than half of patients who underwent horizontal rectus muscle surgery. Among 44 patients she studied, dellen developed in four patents while the remaining had less significant abnormalities, including defects in the precorneal tear film, and fluorescein and/or rose bengal staining. Sterile corneal infiltrates were noted in five patients.

19.1.1 Dellen The term delle (plural dellen) means low ground or pit. Dellen are characterized as shallow, clearly defined excavations at the margin of the cornea. They typically develop within the first 2 weeks after surgery and are generally 1.5–2 mm in diameter and occur following localized evaporation and dehydration of the cornea (>Fig. 19.1). Disruption of the tear film and localized evaporation result in increasing compactness of the corneal stromal lamellae. The base of dellen typically appears hazy and dry and is rarely transparent. Fuchs [2] described the histological aspects of a delle. He found thinning of the epithelium peripherally and observed that the epithelium in the center of the lesion showed irregular thinning of the external stromal layer and Bowman’s membrane and noted the presence of leukocytes beneath Bowman’s membrane. Dellen occur commonly after strabismus surgery, with a reported incidence of between 0.3% and 22.45% [3]. Tessler and Urist [4] retrospectively studied 170 cases of horizontal rectus

muscle surgery. Dellen formation occurred in 6.5% of patients operated with a limbal approach compared with 2.2% for those operated using a nonlimbal approach. Dellen probably often go undiagnosed because subjective symptoms may be absent and clinical findings may be subtle. Additionally, strabismus surgery is often performed on small children who cannot be readily examined at a slit lamp. Mai and Yang [3] reported the occurrence of dellen after 22.45% of strabismus surgeries in patients who had undergone a rectus muscle recession or resection. The occurrence of dellen was much more common after rectus muscle resection procedures (47.75%) compared to rectus muscle recession procedures in which this complication occurred in only 5.13% of eyes. These investigators performed rectus muscle recession surgery through a limbal conjunctival incision with recession of the conjunctival flap to the insertion of the rectus muscle. The surgical approach used for rectus muscle resections was not clearly delineated in the report. It has been our experience that dellen are much more likely to occur following the very large resections, while small resections are not likely to be associated with dellen formation. Mai and Yang [3] related the formation of dellen after strabismus surgery to changes in the tear film breakup time before and after surgery. The average preoperative tear film breakup time was 28.75 seconds (10.96–91.80 s). The breakup time was reduced in all patients postoperatively, regardless of the procedure performed and whether or not a delle formed.

Fig. 19.1. Corneal delle following strabismus surgery

186

Anterior Segment Complications

The tear film breakup time in the group that experienced dellen formation was 23.22 s preoperatively and was reduced to 8.61 s postoperatively. In comparison, in the group that did not experience dellen formation, the tear film breakup time for those who had undergone a rectus muscle recession was 30.22 s preoperatively compared to 22.25 s postoperatively. For those without dellen formation who had undergone a rectus muscle resection, the breakup time was 29.71 s preoperatively and 15.83 s postoperatively. They concluded that local corneal dehydration and ultimately dellen formation was caused by reduced tear film breakup time. It has also been our anecdotal experience that dellen formation is more likely following rectus muscle resection surgery compared with rectus muscle recession surgery. Additionally, dellen formation appears to be more common in our experience following strabismus surgery performed through a limbal incision, though we have not formally studied this association. Common to almost all cases of dellen formation is elevation of the bulbar conjunctiva near the limbus adjacent to the lesion. It seems logical that limbal incisions and rectus muscle resection procedures, both of which tend to produce a greater degree of bulbar conjunctival edema and elevation near the limbus, would be associated with an increase in the formation of dellen. While we agree that the relationship between dellen formation and tear film breakup is interesting, we do not advocate the need for assessment of the breakup time prior to strabismus surgery. We have seen corneal dellen formation following horizontal rectus muscle surgery, but have never seen dellen formation after vertical rectus muscle or oblique muscle surgery. Presumably this is because tear film evaporation and corneal drying are more likely to occur in the middle of the open palpebral fissure compared to the more protected areas superiorly and inferiorly. Though most patients with dellen are asymptomatic, some experience excessive lacrimation. Patients may also complain of mild ocular discomfort, but it has been our impression that dellen rarely produce pain. While usually mild and self-limiting, serious complications have been reported following formation of dellen. Insler and co-workers [5] reported the formation of a descemetocele in a patient who developed a long-lasting corneal delle following vitrectomy surgery. The patient required a patch graft to the cornea to prevent corneal perforation. Zehl and Snell [6] reported corneal ulceration with dellen-like formation “in a region where there was considerable conjunctival thickening adjacent to the limbus,” in a patient with paralysis of cranial nerves 5, 6, and 7 who underwent strabismus surgery. Treatment of dellen involves corneal rehydration and measures to reduce limbal conjunctival elevation. We generally prescribe a lubricating ophthalmic ointment three to four times per day to the affected eye. Dellen usually resolve within a few days to a week, accompanied by spontaneous reduction in bulbar conjunctival swelling as postoperative healing progresses. We have occasionally seen corneal dellen and bulbar conjunctival swelling persist for longer periods of time, prompting empirical use of topical steroids three to four times a day in an effort to hasten healing of the conjunctiva, which will translate into improvement of the associated corneal pathology. While we have not experienced serious complications associated with corneal dellen formation, the possibility of a serious compli-

Chapter 19

cation exists and patients with corneal dellen are monitored more closely than the standard postoperative patient. Patients with an underlying tear film deficiency may be at highest risk and may require closer follow-up.

19.1.2 Corneal Abrasions Corneal abrasions can occur due to unintentional corneal trauma caused by needles, sutures, and other instrumentation during surgery. Spontaneous corneal epithelial defects may be seen during strabismus surgery in patients with epithelial basement membrane disturbances. Hydration of the cornea during surgery may reduce the occurrence of spontaneous corneal erosion in patients with basement membrane disease. In general, however, we favor minimized application of balanced salt solution and other hydrating solutions during strabismus surgery, because these solutions tend to cause edema of exposed Tenon’s fascia in the operative site. Hydration of Tenon’s fascia can complicate surgery and can make closure more difficult. A corneal abrasion occurring during strabismus surgery should be managed using ordinary measures. If the abrasion is small, we generally do not recommend an eye patch but we do advise patients and/or parents of the presence of the corneal epithelial defect and we follow the patient more closely after surgery until the epithelial defect heals.

19.1.3 Corneal Ulcer Both infectious and noninfectious corneal ulceration have been reported following strabismus surgery. We are aware of one unpublished case of bilateral pseudomonas microbial keratitis that resulted following strabismus surgery in which the surgeon utilized corneal bridle sutures to position the eyes for surgery. The use of corneal bridle sutures imposes an unnecessary risk of serious ocular infection by disruption of the corneal epithelium and stroma and should be avoided. Positioning of the eye for surgery can be accomplished through other means including placement of bridle sutures through the conjunctiva or use of positioning forceps. Zehl and Snell [6] reported a case of serious corneal complication following strabismus surgery to realign the eyes of a child with a left sixth nerve palsy. The child had a history of a left cerebellar hemisphere astrocytoma and concurrent fifth and seventh nerve palsies. A left lateral rectus muscle resection and left medial rectus muscle free tenotomy were performed. Two weeks after surgery the authors reported that “corneal ulceration had supervened with dellen-like formation temporally, in a region where there was considerable conjunctival thickening adjacent to the limbus.” Additional infiltrative lesions developed 2 weeks later. Supportive therapy with a therapeutic soft contact lens and antimicrobial therapy in the form of topical antibiotics resulted in healing of the corneal lesions and 6 months following surgery the cornea remained stabile. The authors believed that extraocular muscle surgery in patients with complete loss of fifth and seventh nerve function

 

is associated with an increased, yet not unacceptable risk of complications. Wintle and coworkers [7] reported the development of an inferior corneal ulcer in a patient with Pendred syndrome. This autosomal recessive condition is associated with congenital deafness and thyroid goiter. The child underwent a transposition procedure in both eyes to treat a bilateral sixth nerve palsy. Corneal ulceration of the left eye developed 2 months following surgery, without significant ocular discomfort. Corneal sensation testing revealed normal sensation of the right eye but significantly reduced sensation of the left cornea. The ulceration responded to treatment with topical antibiotics, ocular lubricants, and a glue tarsorrhaphy. The author stressed the importance of determining corneal sensation in patients with atypical disease. While this may be good advice for a rare and unusual patient, the routine testing of corneal sensation prior to strabismus surgery is unnecessary. Several ocular diseases can cause reduced corneal sensation, including a herpes simplex keratitis, postoperative anterior segment ischemia, intraoperative damage to the long posterior ciliary nerves or ciliary ganglion, and congenital absence of corneal sensation. Caution should obviously be exercised when performing any surgery, including strabismus surgery, on patients who are at increased risk for development of corneal complications due to exposure keratopathy and/or reduced corneal sensation. The presence of one of these conditions, however, is not a contraindication to strabismus surgery, but affected patients should be made reasonably aware of the potential risks associated with surgery and should not undergo surgery unless a significant clinical benefit is anticipated. Detailed preoperative discussion with patients and/or families is important and such patients should be followed carefully after surgery. Frequent topical lubrication is helpful and such patients should be advised of the warning signs of a serious corneal complication. The most common condition that the strabismus surgeon is likely to encounter in which there is a substantial risk of a corneal complications is the surgical management of patients with a third cranial nerve palsy. Such patients present a complex treatment matrix and the risk-to-benefit profile must be evaluated on a case-by-case basis. Affected patients desire an eye that is surgically aligned in the primary position and an upper eyelid that is surgically elevated to match their unaffected eye. Absence of a Bell’s phenomenon and lagophthalmos resulting from ptosis repair combine to place the ocular surface in a compromised situation. Our typical surgical paradigm for adult patients with a third nerve palsy is to manage their strabismus and ptosis in separate operations. Ptosis repair is not considered until ocular alignment in the primary position has been optimized and the patient has demonstrated ability to comfortably fuse when the lid is elevated with a reasonably comfortable head posture or demonstrates that they are not significantly bothered by diplopia from residual ocular misalignment. Ptosis surgery is offered to complete the procedure after a detailed discussion with the patient. It is very important to discuss the goals of ptosis repair with patients and families, which for us is undercorrection (>Fig. 19.2). The goal of ptosis undercorrection is much easier to accept when discussed prior to surgery

19.1  Corneal Complications

and patients and parents may be rather disappointed if they do not become fully aware of the surgical goals until after surgery. Patients who are unable to achieve comfortable single vision or who only achieved a very small field of single vision following strabismus surgery may not be good candidates for aggressive ptosis repair. We prefer the use of a frontalis suspension technique for correction of ptosis in this setting, because we believe the procedure results in a more predictable lid position and that the surgery is easier to reverse, if needed, should a corneal complication related to exposure develop. Fascia lata suspensions should be avoided because they are more difficult to reverse. We will generally use silicon rods or suture to accomplish frontalis suspension in patients with a third nerve palsy and always aim to undercorrect the ptosis to minimize the risk of corneal exposure complications. Silicone rods may be especially useful in this setting as they may allow better closure in patients with good orbicularis function. We have treated several patients with corneal exposure following surgery to treat a third cranial nerve palsy. These complications have generally been mild, consisting of corneal drying, punctuate erosions, and occasionally large epithelial erosions. Aggressive lubrication, occasionally accompanied by a temporary tarsorrhaphy, has generally resulted in healing with a good outcome. We had one child who presented 6 months following surgery with microbial keratitis. Fortified

Fig. 19.2. Intentional undercorrection of ptosis following strabismus surgery in a child with a bilateral third nerve palsy

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topical antibiotics resulted in healing of the corneal ulcer, but persistent exposure problems ultimately forced us to reverse his ptosis repair. The resulting corneal scar was also associated with development of severe deprivational amblyopia.

19.1.4 Filamentary Keratitis Mild filamentary keratitis is not infrequently seen following strabismus surgery particularly in patients who have concurrent ptosis or who develop temporary mechanical ptosis following strabismus surgery. The condition is generally mild, asymptomatic, and self-limited. Pons and Rosenberg [8] reported a patient who developed filamentary keratitis following a recess/resect operation to treat a third nerve palsy (>Fig. 19.3). The patient responded favorably to standard treatment including debridement, ocular lubrication, punctal plugs, and topical steroids. Her symptoms were controlled with long-term use of an extended wear soft contact lens.

19.1.5 Reduced Endothelial Cell Count Müller and coworkers [9] reported an unexpectedly high loss of endothelial cell density in children following strabismus surgery, and suggested that inflammatory stress and differences in eye growth associated with strabismus surgery in children might be the cause. The implications of this findings for children undergoing strabismus surgery is unclear and probably not clinically important.

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19.1.6 Corneal Toxicity Hamed and co-workers [10] reported a case of presumed accidental corneal exposure to Hibiclens® (chlorhexidine 4% and detergent) in two patients during craniofacial surgery and cataract surgery, respectively. Both patients developed severe and permanent corneal ectasia and opacification. They subsequently confirmed toxicity of this agent to the cornea in rabbit eyes. Hibiclens®, sometimes utilized for surgical preparation of operative sites, should not be used in preparation of patients for ophthalmologic surgery. We utilize 5% povidone iodine for preoperative preparation (Chap 5) prior to strabismus surgery both because of its lack of significant toxicity to the ocular surface and its excellent role in reducing the normal bacterial flora of the ocular surface [11].

19.2 Conjunctival Complications Complications involving the conjunctiva are probably the most common problems that occur during or following strabismus surgery. Complications vary from anatomical defects related to closure of the conjunctiva to infection, and can range in severity from trivial to vision threatening. Conjunctival closure problems occur most commonly following strabismus surgery performed through a limbal incision, but can occur with a fornix incision also. Careful analysis of conjunctival anatomy while in the operating room prior to starting surgery is key to accurate closure of the conjunctiva at the end of surgery.

19.2.1 Inadvertent Advancement of the Plica Semilunaris Conjunctivae

Fig. 19.3. Filamentary keratitis of a patient’s left eye 1 week following a recess/recess operation to treat a third cranial nerve palsy. (Reprinted from [8] Journal of AAPOS, Volume 8, Pons ME, Rosenberg SE, Filamentary keratitis occurring after strabismus surgery, pp 190–191, 2004, with permission from American Association for Pediatric Ophthalmology and Strabismus)

The term plica refers to an anatomical structure in which there is folding over of the parts. The plica semilunaris conjunctivae (referred to as plica here) represents a fold in the palpebral conjunctiva of the medial angle of the conjunctiva. It serves no particular function in the human eye but when surgically malpositioned it can present a serious cosmetic defect and may cause restriction of abduction. Inadvertent advancement of the plica typically results from the suturing of plica to the conjunctiva adjacent to the limbus. This complication may occur following strabismus surgery using a limbal incision. During standard limbal surgery, the anterior aspect of the limbal conjunctival flap can become folded beneath the plica. At the conclusion of the surgery, the surgeon attempts to identify the anterior edges of the conjunctival flap. The plica may have become hydrated and swollen during surgery and the surgeon is lulled into believing that he/she has grasped the anterior corners of the conjunctival flap, when in fact the edges of the plica have been inadvertently grasped. Figure 19.4 demonstrates how easily this can occur. In the figure, the surgeon is intentionally holding the plica against the limbus at the conclusion of a case. Hydration of the plica dur-

 

19.2  Conjunctival Complications

ing surgery produces the casual appearance that the surgeon has accurately grasped the anterior corners of the limbal conjunctival flap. Only by careful study of the anatomy will the surgeon recognize that the medial angle of the eye appears abnormal and that the swollen plica has been inadvertently advanced forward. Once the mistake is recognized, key landmarks can be easily identified. This complication is most likely to occur in the hands of a surgeon who performs strabismus surgery infrequently. In our experience, disorientation during closure appears to occur most commonly with resident and fellow surgeons in the early part of their training. Advancement of the plica may be more likely following prolonged surgery and is most prone to occur after an extensive reoperation and in older patients with extremely thin conjunctiva. The use of excessive hydration during surgery may result in greater distortion of the anatomy by increasing edema of tissues in the operative site and, thus, we do not use a

large amount of hydrating fluids during strabismus surgery in part to avoid obscuring important surgical landmarks. Prevention of inadvertent advancement of the plica should begin before surgery is initiated. The surgeon should examine the anatomy of the medial aspect of the eye and take care to restore the anatomy to its preoperative state at the time of closure. In cases where we anticipate a difficult closure we will often place 6-0 Vicryl marker sutures (>Fig. 19.5) at the anterior corners of the conjunctival flap before proceeding with surgery. At the conclusion of the case, these corner markers are easy to locate and they help facilitate accurate conjunctival closure. To facilitate closure in routine cases for the surgeon who performs strabismus surgery infrequently, we often recommend using a sterile methylene blue skin marking pen to outline the conjunctiva prior to making the incision, a process that facilitates both accurate creation of the conjunctival incision and closure at the end of the case (>Fig. 19.6).

Fig. 19.4a,b. Inadvertent advancement of the plica semilunaris during closure of a limbal incision: a appearance of the medial angle of the conjunctiva when the plica is held against the limbus, demonstrating how the surgeon can be fooled into believing that the edge of the

conjunctival flap has been identified, and b appearance of the same eye after release of the plica and acquisition of the edges of the conjunctival flap

Fig. 19.5. Placement of Vicryl suture tags on the corners of the conjunctival flap during the initial stages of surgery to facilitate identification of the flap at the conclusion of surgery

Fig. 19.6. Use of a sterile methylene blue skin-marking pen to outline the conjunctiva prior to incision facilitates later closure of the conjunctiva

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19.2.1.1 Limbal Incision Closure Tips Closure of a limbal incision should involve three distinct steps. If followed, the risk of inadvertent advancement of the plica is extremely low. The first step involves recognizing that the anterior aspect of a limbal flap often becomes coiled under the plica and that the surgeon must uncoil the anterior aspect the flap (>Fig. 19.7a). The second step is then to lightly grasp the underlying Tenon’s fascia near the corners of the limbal flap. Tenon’s fascia is lightly stretched anteriorly, resulting in uncoiling of the anterior-most aspect of the conjunctival flap (>Fig. 19.7b). Finally, sutures are placed in the corners of the conjunctival flap to complete the closure. We have not been involved in the acute care of any patient who has had inadvertent advancement of the plica during strabismus surgery. Because infolded conjunctiva can fuse to adjacent conjunctiva [12] making repair very difficult, we recom-

Chapter 19

mend immediate surgery to correct the problem if diagnosed in the early postoperative period. We have treated several patients who sought treatment for plica advancement months or years after surgery. The complication can be identified by the presence of a beefy, thickened appearing medial conjunctiva (>Fig. 19.8). The eye may also become esotropic as a result of mechanical restriction produced by the shortened medial conjunctival fornix. We have treated several patients with chronic advancement of the plica to the limbus. Early efforts to correct this problem involved attempting to dissect conjunctival/plica adhesions followed by uncurling of the infolded conjunctiva with reattachment of the anterior conjunctiva to its proper position near the limbus. These early attempts were immediately recognized as futile. The infolded conjunctiva was always found to be severely contracted and even when we were able to free these adhesions, the contracted conjunctiva was thickened, unsightly, and could not be effectively repositioned near the limbus. Even re-

Fig. 19.7a,b. Steps in the closure of a limbal incision. a Identify and uncoil the conjunctival flap. b Lightly grasp the underlying Tenon’s fascia near the corners of the flap and stretch it anteriorly, a step that

further uncoils the anterior aspect of the flap followed by placement of sutures in the corners of the conjunctival flap

Fig. 19.8. Appearance of the medial conjunctiva in a patient who experienced inadvertent advancement of the plica semilunaris to the limbus during strabismus surgery through a limbal incision 7 years earlier

Fig. 19.9. Improvement of postoperative appearance following surgical repair of longstanding advancement of the plica semilunaris to the limbus. (Same patient as in figure 19.8)

 

cession of the conjunctival flap was not effective. The plica has been markedly stretched in all of these cases as well. Because of this, even when released from the limbus, the plica tended to migrate back and reattach anteriorly after surgery. Our more recent cases have enjoyed a greater measure of success. A large incision is fashioned at the limbus followed by removal of the medial conjunctiva and the plica almost to the caruncle (>Fig. 19.9). A small amount of the elongated plica is left intact medially to create a more anatomically normal appearance of the medial conjunctival angle postoperatively. We have found it necessary to suture the remaining plica to the sclera or to the medial rectus muscle insertion to reduce the tendency of this structure to attach more anteriorly during the postoperative period. Significant improvement can be achieved with surgery, though the cosmetic results are not perfect (>Fig. 19.9).

19.2.2 Retraction and Coiling

19.2  Conjunctival Complications

excise the conjunctiva ridge, leaving the underlying sclera bare. This technique typically produces excellent resolution and results in an excellent postoperative appearance. To reduce the risk of conjunctival retraction and coiling following strabismus surgery through a limbal incision, several steps may be helpful, and may be especially useful in older patients and in others with attenuated conjunctiva. Additional sutures placed along the radial relaxing incisions in addition to sutures placed at the corners of the conjunctival flaps may be of value. The placement of a suture at the limbus midway between the two corner sutures can reduce tension on the corner sutures as well. The use of a small-diameter needle may result in less tearing of the conjunctiva during suture placement, reducing the risk of the suture tearing out of the conjunctiva postoperatively with resultant retraction and coiling.

19.2.3 Chemosis

Even following a properly closed limbal incision, the edges of the conjunctival flap can sometimes retract from the limbus before it has sufficiently formed an adhesion to the underlying sclera. While usually tolerated well, this complication can produce an unsightly ridge posterior to the limbus (>Fig. 19.10). The resulting ridge can be of significant cosmetic concern to the patient, and also can produce symptoms of ocular discomfort, resulting from tear film disruption. We usually recommend observation in the early postoperative period, because in most cases the thickened conjunctiva will become smooth and sufficiently flattened as the eye heals that no additional treatment is needed. If the problem persists for weeks or months following surgery, we have occasionally found it necessary to

Chemosis represents edema of the bulbar conjunctiva, which produces swelling of the conjunctiva around the cornea. It occurs to a mild degree in all patients undergoing strabismus surgery, but can occasionally be pronounced. The patient in Fig. 19.11 underwent bilateral, symmetric lateral rectus muscle recession in both eyes through a fornix incision. Five days after surgery, the right eye exhibited marked chemosis, while the left eye was healing normally. There was no evidence of periocular on intraocular infection. Chemosis of this severity is rarely seen following routine strabismus surgery. Chemosis can disrupt the suspensory attachments to the conjunctival fornix through hydraulic dissection. Prolonged prolapse of the conjunctiva may result in fusion of the folds together requiring excision [12].

Fig. 19.10. Perilimbal ridge produced by coiling and retraction of a limbal conjunctival flap following surgery

Fig. 19.11. Severe, benign unilateral chemosis in a patient who underwent symmetric bilateral strabismus surgery

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Treatment is initially supportive, consisting of aggressive lubricating ophthalmologic ointments, with the addition of cellophane tents at night if the swollen conjunctiva protrudes anterior to the eyelids. Topical steroids are often prescribed and appear to be of value. This conservative treatment regimen will usually result in significant improvement or resolution within a few days to a week. When severe and prolonged, we have successfully managed chemosis by placement of temporary sutures in the conjunctival fornix to invaginate the prolapsed conjunctiva, as recommended by Malone and Tse [13].

Chapter 19

pre and post invagination suture appearance of a patient with mild, but very symptomatic residual chemosis protruding over the lower eyelid 3 weeks after strabismus surgery. While hydration alone would have normally been satisfactory in this mild situation, this patient was returning to his home country overseas and there was a need to hasten resolution of the problem prior to his departure.

19.2.3.1 Technique for Correction of Prolapsed Inferior Conjunctiva Topical proparacaine is applied to the conjunctival surface. After a sterile preparation of the lids, the lower eyelid is infiltrated with 2% lidocaine hydrochloride with 1:100,000 dilution of epinephrine. Two or three double-armed absorbable sutures, such as 4–0 chromic gut sutures or 6-0 Polyglactin 910TM (Vicryl®), are inserted in mattress fashion to reposition the prolapsed conjunctiva into the fornix of the lower eyelid. The needles are passed into the dome of the prolapsed conjunctiva, through the inferior fornix, exiting the skin 8–9 mm below the lash margin (>Fig. 19.12). The second pass is made several millimeters from the first and the two suture ends are then tied on the skin surface. Upon tightening the sutures, the prolapsed conjunctiva is invaginated and will re-form the inferior fornix. Malone and Tse [13], who used this technique to manage prolapsed conjunctiva after retinal surgery, described use of this technique for prolapsed upper fornix conjunctiva also, though we have not seen involvement of the upper conjunctiva following strabismus surgery. They also recommended temporary tarsorrhaphy in conjunction with placement of the mattress sutures. We have not found temporary tarsorrhaphy necessary, but rather rapid healing has been seen in our patients using the mattress suture technique alone. Figure 19.13 shows the

Fig. 19.12. Suture placement to invaganate protruding inferior conjunctiva. Double-armed absorbable sutures are passed into the dome of the prolapsed conjunctiva, through the inferior fornix, and exit the skin 8–9 mm below the lash margin. When the sutures are tightened, the prolapsed conjunctiva is invaginated to re-form the inferior fornix. [With permission from Malone TJ, Tse DT, Archives of Ophthalmology 108; 890–891. Copyright (c) (1990) American Medical Association. All rights reserved]

Fig. 19.13. Preoperative (right) and postoperative (left) appearance of the conjunctiva following placement of sutures to treat mild but long-standing conjunctival chemosis protruding over the lower eyelid

 

19.2.4 Pyogenic Granuloma The term pyogenic granuloma is a misnomer, because the lesions are neither pyogenic nor granulomas. Histological examination of these lesions has found them to be composed of mixed acute and chronic inflammatory cells, with capillary proliferation in a lobular pattern [14]. Clinically, pyogenic granulomas appear as a fleshy red mass with relatively rapid growth (>Fig. 19.14). The lesion is a proliferative fibrovascular response to previous trauma including surgery. The lesions can be mistaken for suture granulomas, Tenon’s cysts, or tumors and are a recognized complication of many ocular surgeries where the conjunctiva is manipulated. Pyogenic granulomas have been described after pterygium excision, chalazia incision and drainage, placement of orbital implants, nasolacrimal duct probing with silicone tube placement, insertion of silicone punctal plugs, blepharoplasty, and eye muscle surgery [15–19]. The incidence of pyogenic granulomas has been reported as occurring after 1% of all conjunctival incisions and typically occurs 3–4 weeks after surgery. Espinoza and Lueder [20] reported pyogenic granuloma formation in 2.1% of strabismus operations. This rate is higher than our anecdotal experience, in which this complication is rare. In most cases, these lesions will resolve spontaneously. Many surgeons recommend the use

19.2  Conjunctival Complications

of topical steroids although their efficacy has not been proven (>Fig. 19.14). The average duration of treatment is 2–3 weeks. Surgical excision may be required for pyogenic granulomas that fail to resolve after topical treatment and/or observation alone. Reoccurrence following excision is extremely rare [20].

19.2.5 Prolapse of Tenon’s Fascia Occasionally extrusion/exposure of Tenon’s fascia through the conjunctival incision occurs following strabismus surgery. This complication can be avoided by ensuring that the edges of the conjunctival incision are well opposed or sutured following surgery. If a large amount of Tenon’s fascia is noted to be extruding through the conjunctival incision at the end of the case, we will either excise the extruding Tenon’s fascia or place additional sutures in the conjunctiva to fully internalize the exposed fascia. Occasionally, however, a patient will present postoperatively with exposed Tenon’s fascia, sometimes with the exposed Tenon’s fascia stringing from the wound and even over hanging the eyelid (>Fig. 19.15). If the patient is cooperative, the exposed Tenon’s fascia can be trimmed flush with the conjunctival surface. Topical steroids can be used in cases where excision is not possible and resolution typically occurs within days or weeks.

Fig. 19.14a,b. Pyogenic granuloma that occurred following medial rectus muscle recession through a fornix incision (a). Resolution after topical steroid administration (b)

Fig. 19.15. Tenon’s fascia extruding from the conjunctival fornix incision 1 week following strabismus surgery

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19.2.6 Epithelial Inclusion Cyst Subconjunctival epithelial inclusion cysts occur infrequently as a complication of strabismus surgery. They can occur anywhere in the operative field, but most commonly occur adjacent to conjunctival incisions or near the new muscle insertion into the sclera. Ullrich and coworkers [21] have even reported a patient with bilateral acquired epithelial cysts in the belly of the medial rectus muscles. Simple acquired conjunctival epithelial cysts are thought to arise from inclusion of conjunctival epithelial cells into the substantia propria or the sclera. Nests of conjunctival epithelial cells that have become deposited during strabismus surgery later proliferate, forming a central cavity and ultimately forming a visible cyst. The wall of the cyst is usually composed of nonkeratinized conjunctival epithelium and may contain goblet cells (>Fig. 19.16). Epithelial inclusion cysts have a tendency to enlarge over time and thus removal of an epithelial inclusion cyst is recommended when the diagnosis is made or suspected. Untreated, inclusion cysts can persist indefinitely and can enlarge dramatically. Figure 19.17 demonstrates the anterior aspect of a large epithelial inclusion cyst present for more than 40 years following medial rectus muscle recession surgery. Prior to surgical excision, the patient’s ophthalmologist had performed

Fig. 19.16. Epithelial inclusion cyst lined with nonkeratinized conjunctival epithelial cells

Chapter 19

needle aspiration of the cyst on several occasions, with rapid recurrence. At surgery, the cyst extended well into the posterior orbit. When an epithelial inclusion cyst forms at the site of muscle reattachment to the sclera, growth of the cyst can result in disruption of the muscle insertion [22], causing movement of the muscle insertion posteriorly, and recurrent strabismus. Failure to recognize that the muscle is attached to the cyst can result in detachment of the muscle with worsening of the patient’s strabismus [22]. Figure 19.18 demonstrates an epithelial inclusion cyst removed intact from an 18-year-old woman who had undergone four previous strabismus operations involving right superior rectus muscle. After her most recent surgical procedure, performed 7 years prior to our evaluation, she noted the gradual onset of a right hypotropia and retraction of her right upper eyelid. Examination revealed a right hypotropia, right upper eyelid retraction and proptosis with hypoglobus (>Fig. 19.18a). Computed tomography revealed the presence of a large cystic structure in the superior aspect of the orbit (>Fig. 19.18b). The anterior aspect of the cyst was found 12 mm from the limbus. The cyst extended more than 10 mm posteriorly and the superior rectus muscle was attached to the posterior aspect of the cyst (>Fig. 19.18c). Removal of the cyst followed by advancement and reattachment of the superior rectus muscle to the globe resulted in marked improvement of both her hypotropia and her lid retraction. Epithelial inclusion cysts occur infrequently enough that studies to investigate their cause and to study surgical techniques to minimize their occurrence are not practical. Though we do not have evidence to support the following recommendations to reduce the risk of epithelial inclusion cyst formation, common sense would seem to support several useful concepts. First, we recommend creating conjunctival incisions in the most uniform, least disruptive manner possible. During closure of the conjunctiva, care should be taken to ensure that the conjunctival edges are reapproximated accurately, making sure that the edge of the conjunctival incision is not coiled into the wound. Care should also be taken when pulling suture through scleral tunnels created to attach the extraocular mus­ cles to the globe to reduce the risk of an epithelial inclusion cyst forming at the muscle insertion. We are concerned that, if

Fig. 19.17. Anterior aspect of a large epithelial inclusion cyst present for more than 40 years after left medial rectus muscle recession

 

19.2  Conjunctival Complications

Fig. 19.18a–c. Epithelial inclusion cyst following multiple operations on the superior rectus muscle. a Preoperative appearance demonstrating proptosis, hypoglobus and eyelid retraction. b Computed tomo­ graphy demonstrating a large cystic structure in the superior orbit. c Note that the superior rectus muscle is attached to the posterior edge of the cyst

Fig. 19.19. Dragging of conjunctiva into the scleral suture tunnels could implant conjunctival tissues in the scleral tract leading to later development of an epithelial inclusion cyst

the conjunctiva becomes adherent to the suture and is pulled into the scleral tunnels, conjunctival epithelial cells may become deposited in the scleral tunnels resulting in later development of an epithelial inclusion cyst (>Fig. 19.19). While very small epithelial inclusion cysts can be effectively removed through a small conjunctival incision placed adjacent to the cyst, we have found that most medium to large epithelial inclusion cysts are best removed through a standard limbal conjunctival incision, similar to the limbal incisions created for surgery on the rectus muscles. Limbal incisions are familiar to most strabismus surgeons, they facilitate excellent exposure of the cyst, and they allow the surgeon to maintain control of

adjacent muscles during excision, thereby reducing the risk of muscle injury. We recommend isolation of the adjacent muscle on a muscle hook to help ensure the safe removal of the cyst without accidental disinsertion of the muscle if the cyst is large and located close to the muscle. We have treated one case of a lost muscle that developed during removal of an epithelial inclusion cyst that went unrecognized by the surgeon until the postoperative period when the patient presented with a large consecutive deviation and duction deficit. The goal of surgery should be to remove epithelial inclusion cysts intact. After creating a limbal incision, the conjunctiva and Tenon’s fascia overlying and adjacent to the lesion

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are sharply dissected (>Fig. 19.20a). Care should be taken to avoid manipulating the cyst with forceps, as the cyst can easily be ruptured during manipulation. Once the cyst has been fully exposed, it should be carefully excised from the underlying sclera. Attachment of the cyst to the underlying sclera is typically very firm and care must be taken to transect these fine but firm attachments to the underlying sclera without rupturing the cyst (>Fig. 19.20b). Epithelial inclusion cysts that develop at the muscle insertion and result in migration of the muscle posteriorly are typically only attached to the sclera at the muscle insertion, and this attachment tends to be quite firm as well.

Chapter 19

While removal of a conjunctival epithelial inclusion cyst intact seems a reasonable objective of surgery, we have had several cysts rupture during removal. When this occurs, we have excised all visible elements of the cyst, irrigated the operative site in an attempt to wash away any stray epithelial cells, and applied cautery to the sclera where the cyst was attached. Thus far, none have recurred, including those that have ruptured during removal. After removal of the cyst, the conjunctiva should be closed with interrupted absorbable suture (>Fig. 19.2c). Patients are placed on a combination steroid and antibiotic drop 4 times per day for 1 week. Healing of the conjunctiva generally occurs in a manner similar to conjunctival healing following standard strabismus surgery. Hawkins and Hamming [23] described a simple office technique to treat small conjunctival inclusion cysts. Following administration of a topical anesthetic agent, a high temperature (2200ºF) battery-powered ophthalmic cautery unit was applied to the cyst under slit lamp visualization. It was applied directly to the surface of the cyst until fluid was released from the cyst and the base of the cyst was then cauterized. A combination steroid–antibiotic ointment was used postoperatively for 1 week. The procedure resulted in rapid resolution with no recurrence in the three patients they treated (>Fig. 19.21). Freedman has described another method to remove epithelial inclusion cysts (personal communication with Richard Freedman). He suggests injecting the cyst with methylene blue dye. The contents of the cyst will drain through the injection site leaving the stained cyst wall easily visible. The cyst can then be readily removed with improved visualization (>Fig. 19.22). We have found this technique to be useful in selected cases.

19.2.7 Sudoriferous Cyst We have seen several patients referred to us with chronic pain for months or years following strabismus surgery who had no external signs of ocular abnormalities. Surgery to correct residual strabismus, typically also associated with a concurrent duction limitation, has revealed the presence of a sudoriferous cyst in several cases. A sudoriferous cyst is an implantation cyst of sweat gland origin. These cysts presumably arise through implantation of cells from the accessory lacrimal gland or glands of Moll. They are lined by cuboidal epithelium that is similar to the parent gland or duct. Grossly, they may contain a clearyellow or viscous, brown-yellow material that may resemble an abscess in appearance, but will be culture negative. The lesions should be treated by complete surgical excision, which in our cases has also resulted in resolution of the chronic ocular discomfort/pain that our patients had experienced prior to surgical removal.

Fig. 19.20a–c. Removal of an epithelial inclusion cyst: a a limbal incision is created and b tissues overlying the cyst dissected and the cyst is removed intact; c following removal

 

Fig. 19.21a,b. a Conjunctival cyst on the nasal conjunctiva of a patient’s right eye 5 months after strabismus surgery and b 2 months after the cyst was cauterized. (Reprinted from [23] Journal of AAPOS, volume 5, Hawkins AS, Hamming NA, Thermal cautery as a treatment

19.2.8 Subconjunctival Abscess The occurrence and treatment of a subconjunctival abscess following strabismus surgery is discussed in detail in Chap. 22, and is reviewed here briefly. A subconjunctival abscess usually presents with pain that is in excess to that experienced by the typical postoperative patient, marked conjunctival injection and elevation of the overlying conjunctiva. An abscess is often visible and obvious through the overlying thin conjunctiva (>Fig. 19.23). When an abscess is diagnosed or suspected, surgical drainage should proceed as soon as possible. Drainage can be done in the office or in the operating room, depending upon the level of patient cooperation, patient age, and the size and location of the abscess. Inspection of the fundus with indirect ophthalmoscopy and slit lamp examination for evidence of intraocular infection is prudent. We have generally prescribed topical and oral antibiotics after abscess drainage. Moxifloxa-

Fig. 19.22. Epithelial inclusion cyst walls stained with methylene blue dye (courtesy of Richard Freeman, MD)

19.2  Conjunctival Complications

for conjunctival inclusion cyst after strabismus surgery, pp 48–49, 2001, with permission from American Association for Pediatric Ophthalmology and Strabismus)

cin, a fourth-generation fluoroquinolone, is our antibiotic of choice because of its broad coverage and it ability to achieve therapeutic levels in the eye after oral administration [24].

19.2.9 Conjunctival Adhesions Simpson and co-workers [25] described the unusual occurrence of broad adhesions between the palpebral and bulbar conjunctiva in a patient who underwent simultaneous surgery on the levator palpebrae superioris muscle of the upper eyelid and lateral rectus muscles. Recognizing that the raw conjunctival surfaces of the palpebral and bulbar conjunctiva could easily make contact after surgery and fuse together, they recommended that eyelid surgery not be performed at the time of strabismus surgery. We concur with this recommendation, if the palpebral conjunctiva is to be incised during lid surgery.

Fig. 19.23. Subconjunctival abscess following strabismus surgery in a patient with diabetes mellitus

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On the other hand, surgery that does not involve incision of the palpebral conjunctiva can be performed simultaneously, if indicated, and we have occasionally found it reasonable to perform lid and strabismus surgery simultaneously.

19.2.10 Primary Amyloidosis Rodrigues and coworkers [26] reported a case of localized amyloidosis involving the conjunctiva overlying the lateral rectus muscle in both eyes of a 13-year-old boy following strabismus surgery (>Fig. 19.24). The lesions recurred following removal, requiring a second intervention to surgically remove the lesions, without further recurrence. The etiology of the lesions was unclear and the details of the strabismus surgical procedure were not available in their published report. While we are aware of cases of systemic amyloidosis involving the conjunctiva and extraocular muscles, we are not aware of any other reports of primary amyloidosis following strabismus surgery.

Chapter 19

19.2.11 Subconjunctival Foreign Bodies Subconjunctival foreign bodies following strabismus surgery can be intentional and unintentional. Unintentional foreign bodies are unusual. Cilia that have fallen into the surgical site are the most common unintentional foreign bodies seen. They are generally asymptomatic, but we treated one patient who was so distressed by the appearance of cilia under the conjunctiva that we ultimately removed it. The most common foreign body that has been intentionally placed at the time of surgery is a nonabsorbable suture. While some strabismus surgeons have advocated routine use of nonabsorbable sutures for some surgical situations [27], we try to avoid permanent sutures when possible. We have seen several long-term problems associated with the use of absorbable sutures. The patient in Fig. 19.25 complained of the appearance of “worms” on the surface of his eyes, the result of a retained permanent suture that was coiled under the conjunctiva. We have seen Mersilene® sutures erode through the overlying conjunctiva months or years after surgery producing chronic ocular discomfort. We have treated several patients with a sterile abscess adjacent to a 6–0 Mersiline® suture, with the onset of symptoms month or years after surgery.

19.2.12 Conjunctival Buttonholes

Fig. 19.24. Localized amyloidosis noted following strabismus surgery. (Reprinted from [26] Rodrigues MM, Cullen G, Shannon G. Primary localized conjunctival amyloidosis following strabismus surgery. Can J Ophthal 1976;11:177–179, with permission)

Buttonholes most commonly occur during reoperation of a patient who has previously undergone strabismus surgery through a limbal incision or other ophthalmologic surgery involving the perilimbal conjunctiva. Following a previous limbal incision, the conjunctiva anterior to the muscle can be tightly adherent to the underlying sclera. Buttonholes can also be seen during primary or secondary strabismus repair in elderly patients with thin conjunctiva when surgery is performed through a fornix or limbal incision. Small buttonholes do not require repair. The conjunctival surface may appear irregular in the immediate postoperative period, but usually will have healed with a smooth and regular appearance when the patient is examined several months following surgery. It is our practice to close larger buttonholes with interrupted absorbable sutures, most common 6–0 plain gut suture. Though they are an unwanted complication, buttonholes are not generally associated with significant cosmetic or functional problems.

19.3 Scleral Complications 19.3.1 Grey Spot

Fig. 19.25. Mersilene® suture coiled in the episcleral space that was visible to a patient more than 10 years after surgery as “worms” in his eyes

The sclera posterior to the rectus muscle insertions is thinner than the surrounding sclera, averaging 0.3 mm in thickness [28]. After disinsertion of a rectus muscle, the dark color of the underlying choroid can often be seen through the thin sclera in this region. This is most obvious following disinsertion of a

 

medial rectus muscle. After recession of a rectus muscle, particularly the medial rectus muscle, a “grey spot” is often visible and its appearance can be quite distressing to some patients (>Fig. 19.26). The grey spot can be subtle or can be quite pronounced. We evaluated one patient who was so distressed by the appearance of a postoperative grey spot that her surgeon had attempted to correct the problem by placement of a pericardial graft to cover the thin sclera (>Fig. 19.27). The result was unsatisfactory, the pericardial graft required removal, and the patient was less distressed by the discoloration of her sclera, thereafter. Advancement of Tenon’s fascia over the area of thin sclera as a primary or a secondary procedure appears to make the scleral grey spot less visible, though data on long-term success with this technique is lacking. We now frequently advance Tenon’s fascia to cover areas of particularly thin sclera posterior to the rectus muscle insertions when the grey spot is noted to be more prominent than usual intraoperatively and we believe that the problem will be a cosmetic issue postoperatively (>Fig. 19.28).

19.3  Scleral Complications

19.3.2 Scleral Ridge Postoperative patients occasionally complain of a ridge or line that can be seen at the site of the original muscle insertion following a rectus muscle recession procedure. This most commonly occurs when a significant muscle stump is left on the sclera and produces irregularity of the overlying conjunctiva postoperatively. It is most likely to be of concern following recession of a lateral rectus muscle, in our experience (>Fig. 19.29). Patients commonly describe a “ridge,” “hole,” or “gutter” in the operated eye. This complication can be minimized by trimming the insertion stump flush with the sclera before closure of the conjunctiva.

Fig. 19.28. Technique for advancement of Tenon’s fascia to help mask the scleral grey spot which occurs as a result of thin sclera posterior to the rectus muscle insertions

Fig. 19.26. “Grey spot” visible medially following recession of the lateral rectus muscle. (Courtesy of Richard A. Saunders, MD)

Fig. 19.27. Unsuccessful attempt to cover a prominent “grey spot” using a pericardial graft. The thick graft was easily visible and ultimately migrated through the conjunctiva and was removed by the patient’s primary surgeon

Fig. 19.29. Obvious scleral ridge visible at the site of the original insertion following rectus muscle recession. This appearance can be minimized by dissecting the muscle stump flush with the sclera

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19.3.3 Scleral Dellen Variation in the size of collagen bundles, random organization of collagen bundles and hydration are thought to be responsible for the sclera being opaque and white. The sclera may become translucent when it is dehydrated by 40% or more [29]. The cause of scleral dellen is thought to be related to tear film disruption, scleral dehydration, and in one case thought to be exacerbated by excessive cauterization of episcleral vessels with development of focal ischemia [30]. Perez [31] reported conservative treatment of a scleral delle using aggressive ocular lubrication and patching, which resulted in rapid resolution of the lesion within 48 h. Lee and coworkers [32] described a patient who developed a severe scleral delle following medial rectus muscle resection through a limbal incision using a bowtype adjustable suture technique and a conjunctival recession (>Fig. 19.30). They remarked that though the sclera appeared extremely thin and perforation appeared imminent, scleral dellen are actually benign lesions. Their patient was managed with

Chapter 19

lubrication and advancement of the conjunctiva. They pointed out that although scleral dellen are benign lesions, the condition must be distinguished from surgically induced necrotizing scleritis. This distinction is not generally difficult because, unlike scleral dellen, surgically induced necrotizing scleritis typically presents with pain, marked inflammation, and is typically associated with systemic immunologic disease.

19.3.4 Scleritis Scleritis has been rarely reported following strabismus surgery. Hemady and coworkers [33] reported a case of scleritis in a 70year-old man following inferior rectus muscle recession due to thyroid-related ophthalmopathy. Gross and coworkers [34] reported a case of necrotizing scleritis in an elderly patient who underwent surgery to treat a gaze palsy and sixth-nerve paresis following a stroke. The patient was treated with topical and systemic corticosteroids and ibuprofen, and ultimately did well.

19.3.5 Agyrosis Bartley and coworkers [35] reported a patient with a pigmented scleral mass from argyrosis following strabismus surgery. The duration of the lesion was unknown and was presumed to have been due to silver nitrate collyrium instillation following strabismus surgery 67 years earlier.

19.4 Anterior Segment/Intraocular Complications Intraocular complications as a result of strabismus surgery are uncommon and are generally associated with perforation of the sclera. Rare reported complications have included hyphema (Chap. 24) and cataracts (Chap. 21). Abnormalities of the iris and pupil, including iris atrophy, corectopia and a poorly reactive pupil can occur as a result of anterior segment ischemia (Chap. 20). Postoperative mydriasis and paralysis of accommodation have been reported following surgery on the inferior oblique muscle. [36] This complication is thought to occur because of stretching of the inferior division of the oculomotor nerve as a result of excessive traction on the inferior oblique muscle during surgery. The resulting accommodative paralysis may recover with time.

References Fig. 19.30a,b. Scleral delle noted a on the 5th postoperative day, and b 1 week after treatment. (Reprinted from [31] Journal of AAPOS, volume 6, Perez I, The “scleral dellen,” a complication of adjustable strabismus surgery, pp 332–333, 2002, with permission from American Association for Pediatric Ophthalmology and Strabismus)

1.

Pedersen LR (1972) Corneal changes following operation for strabismus (rectus surgery) with special reference to occurrence of Dellen. Acta Ophthalmol (Copenh) 50:771–781

  2. 3. 4. 5. 6.

7.

8. 9.

10. 11.

12. 13.

14. 15.

16.

17.

18.

19.

Fuchs A (1929) Pathologic dimples (dellen) of the cornea. Am J Ophthalmol 12:877–883 Mai G, Yang S (1991) Relationship between corneal dellen and tearfilm breakup time. Yan Ke Xue Bao 7:43–46 Tessler HH, Urist MJ (1975) Corneal dellen in the limbal approach to rectus muscle surgery. Br J Ophthalmol 59:377–379 Insler MS, Tauber S, Packer A (1989) Descemetocele formation in a patient with a postoperative corneal dellen. Cornea 8:129–130 Zehl DN, Snell AC (1977) Extraocular muscle surgery in the presence of complete paralysis of the fifth, sixth and seventh cranial nerves. J Pediatr Ophthalmol 14:76–78 Wintle RV, Choong YF, Laws DE (2003) Unilateral corneal anaesthesia and ulceration following squint surgery in a child with Pendred syndrome and bilateral sixth nerve palsy. Br J Ophthalmol 87:1192 Pons ME, Rosenberg SE (2004) Filamentary keratitis occurring after strabismus surgery. J AAPOS 8:190–191 Müller A, Doughty MJ, Watson L (2002) A retrospective pilot study to assess the impact of strabismus surgery on the corneal endothelium in children. Ophthalmic Physiol Opt 22:38–45 Hamed LM, Ellis FD, Boudreault G, Wilson FM 2nd, Helveston EM (1987) Hibiclens keratitis. Am J Ophthalmol 104:50–56 Apt L, Isenberg S, Yoshimori R, Paez JH (1984) Chemical preparation of the eye in ophthalmic surgery. III. Effect of povidoneiodine on the conjunctiva. Arch Ophthalmol 102:728–729 Biglan AW, Chang A, Hiles DA (1980) Prolapse of conjunctiva following external levator resection. Ophthalmic Surg 11:581–583 Malone TJ, Tse DT (1990) Surgical treatment of chemotic conjunctival prolapse following vitreoretinal surgery. Arch Ophthalmol 108:890–891 Schoen FJ (1994) Blood vessels, 5th edn. In: Contran RS (ed) Pathologic basis of disease. WB Saunders, Philadelphia, Pa., p 507 Ferry AP (1989) Pyogenic granulomas of the eye and ocular adnexa: a study of 100 cases. Trans Am Ophthalmol Soc 87:327– 343; discussion 343–347 Lin CJ, Liao SL, Jou JR, Kao SC, Hou PK, Chen MS (2002) Complications of motility peg placement for porous hydroxyapatite orbital implants. Br J Ophthalmol 86:394–396 Coats DK, McCreery KM, Plager DA, Bohra L, Kim DS, Paysse EA (2003) Nasolacrimal outflow drainage anomalies in Down’s syndrome. Ophthalmology 110:1437–1441 Akova YA, Demirhan B, Cakmakci S, Aydin P (1999) Pyogenic granuloma: a rare complication of silicone punctal plugs. Ophthalmic Surg Lasers 30:584–585 Soll SM, Lisman RD, Charles NC, Palu RN (1993) Pyogenic granuloma after transconjunctival blepharoplasty: a case report. Ophthal Plast Reconstr Surg 9:298–301.

References 20. Espinoza GM, Lueder GT (2005) Conjunctival pyogenic granulomas after strabismus surgery. Ophthalmology 112:1283–1286 21. Ullrich CR, Garola RE, Cibis GW (2003) Bilateral extraocular muscle epithelial inclusion cysts as a complication of strabismus surgery. J AAPOS 7:366–367 22. Kushner BJ (1992) Subconjunctival cysts as a complication of strabismus surgery. Arch Ophthalmol 110:1243–1245 23. Hawkins AS, Hamming NA (2001) Thermal cautery as a treatment for conjunctival inclusion cyst after strabismus surgery. J AAPOS 5:48–49 24. Hariprasad SM, Mieler WF, Holz ER (2002) Vitreous penetration of orally administered gatifloxacin in humans. Trans Am Ophthalmol Soc 100:153–159 25. Simpson WA, Downes RN, Collin JR (1989) Unusual complication of strabismus and lid surgery. Ophthal Plast Reconstr Surg 5:131–132 26. Rodrigues MM, Cullen G, Shannon G (1976) Primary localized conjunctival amyloidosis following strabismus surgery. Can J Ophthalmol 11:177–179 27. Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333 28. Helveston EM (1993) Surgical management of strabismus: an atlas of strabismus surgery, 4th edn. Mosby-Year Book, St. Louis, Mo., p 82 29. Watson P (1995) Diseases of the sclera and episclera. Duane’s ophthalmology. Lippincott-Raven, Philadelphia, Chap. 23.1 30. Sharma P, Arya AV, Prakash P (1990) Scleral dellen in strabismus surgery. Acta Ophthalmol (Copenh) 68:493–494 31. Perez I (2002) The “scleral dellen,” a complication of adjustable strabismus surgery. J AAPOS 6:332–333 32. Lee DH, Herion MA, Unwin DR, Cruz OA (2003) Scleral dellen after bilateral adjustable suture medial rectus muscle resection. J AAPOS 7:221–222 33. Hemady R, Sainz de la Maza M, Raizman MB, Foster CS (1992) Six cases of scleritis associated with systemic infection. Am J Ophthalmol 114:55–62 34. Gross SA, von Noorden GK, Jones DB (1993) Necrotizing scleritis and transient myopia following strabismus surgery. Ophthalmic Surg 24:839–841 35. Bartley GB, Buller CR, Campbell RJ, Bullock JD (1991) Pigmented episcleral mass from argyrosis following strabismus surgery. Arch Ophthalmol 109:775–776 36. Bajart AM, Robb RM (1979). Internal ophthalmoplegia following inferior oblique myectomy: a report of three cases. Ophthalmol 86;1401-6.

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Chapter

20

20 20.1 Blood Supply of the Anterior Segment The blood supply to the anterior segment is derived from the long posterior ciliary arteries, the anterior ciliary arteries, and the conjunctival arteries (>Fig. 20.1). The anterior ciliary arteries are thought to provide approximately 70% of the blood supply to the anterior segment with the long posterior ciliary arteries supplying most of the remainder, and the conjunctival arteries supplying a minor component of the blood supply to this region of the eye [1].

Fig. 20.1. Blood supply to the anterior segment

The conjunctival arteries are derived from the palpebral branches of the nasal and lacrimal arteries of the lid (posterior conjunctival arteries) and the anterior ciliary arteries (anterior conjunctival arteries). The anterior ciliary arteries are derived from the ophthalmic artery where they begin as the muscular arteries that supply the rectus muscles before dividing into the anterior ciliary arteries. The anterior ciliary arteries travel along the tendons of the rectus muscles and give off anterior conjunctival arteries just before piercing the sclera. The superior, medial, and inferior rectus muscles each carry two anterior ciliary arteries, while the lateral rectus muscle generally carries only one (>Fig. 20.2). The oblique muscles do not carry an anterior ciliary artery and therefore do not contribute to the anterior segment circulation. The conjunctival and anterior ciliary arteries join to form an episcleral plexus at the limbus. There is free anastomosis between the subconjunctival and episcleral tissue in the region of this plexus between the anterior conjunctival arteries and the terminal branches of the posterior conjunctival arteries. Branches of the anterior ciliary arteries supply the ciliary muscle, the iris and the anterior portion of the choroid. Branches

Fig. 20.2. Anterior ciliary arteries. Note that there are two anterior ciliary arteries with each rectus muscle, except the lateral rectus muscle, which typically has one

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of the anterior ciliary artery also join with branches of the long posterior ciliary arteries to supply the ciliary body and the major arterial circle of the iris. The latter carries blood to the ciliary body, the ciliary processes and the iris.

20.2 Incidence Severe anterior segment ischemia is a rare but potentially sight-threatening complication following strabismus surgery. The incidence of anterior segment ischemia is unknown but a survey of pediatric ophthalmologists published in 1986 estimated that significant anterior segment ischemia occurred in approximately 1 in 13,000 cases [2]. This reported incidence probably underestimates its true occurrence, as mild cases of anterior segment ischemia almost certainly occur without clinical detection. The low incidence of clinically significant anterior segment ischemia probably reflects the protection offered by the rich collateral blood supply from both the long posterior ciliary and anterior ciliary arteries that continue to supply blood to the anterior segment when the anterior ciliary and conjunctival arteries are disrupted. The blood supplied by the posterior ciliary arteries, however, is probably not a significant factor, as evidenced by the fact that anterior segment ischemia does not occur with occlusion of only the posterior ciliary arteries [3]. Therefore, it appears that surgery of the extraocular muscles, specifically the rectus muscles, leads to anterior segment ischemia in at-risk patients, by alteration of the anterior segment circulation through disruption of the anterior ciliary arteries. Disinsertion of a single vertical rectus muscle will result in hypoperfusion to the region of the anterior segment adjacent to the detached muscle. Hypoperfusion can be demonstrated using iris angiography [3–5] (>Fig. 20.3). Hypoperfusion defects

Chapter 20

that occur following vertical rectus muscle disinsertion are generally larger than those following horizontal rectus muscle disinsertion. The anterior ciliary arteries that travel with the vertical rectus muscles supply the majority of the inferior and superior portions of the iris and they have limited collateral connection to the posterior ciliary arteries. Infants and young children do not usually show signs of hypoperfusion following vertical rectus muscle disinsertion. The area of hypoperfusion will decrease with time following redistribution of blood flow from the long posterior ciliary arteries and increase in the capacity of the collateral circulation. An anterior ciliary artery that has been detached from the globe does not reestablish a direct communication with the distal aspect of the vessel [6]. The circulation that is reestablished to the anterior segment is not equivalent to that which was present prior to disruption of the vessel, leaving the patient with a net loss of blood flow to the anterior segment even after maximum collateral circulation has been established. This is important to keep in mind when planning surgery on patients who have had previous strabismus surgery.

20.3 Risk Factors and Prevention Predicting which patients may be at risk for anterior segment ischemia can be difficult. Risk factors for the development of anterior segment ischemia include advanced age, previous rectus muscle surgery, and history of a vasculopathy, such as diabetes and/or hypertension (>Table 20.1). Of these risk factors, advanced age appears to be the most important [2]. Clinically, significant anterior segment ischemia has been reported very rarely in children undergoing strabismus surgery [2, 7]. Anterior segment ischemia has been reported following detachment of only two rectus muscles in older patients and in patients with other concurrent risk factors. Despite anecdotal reports that all four rectus muscles can be detached in children without development of anterior segment ischemia, we always attempt to spare the anterior ciliary circulation associated with at least one rectus muscle. We are not only concerned about the possibility of acute development of anterior segment ischemia following surgery on all four rectus muscles, but also of potential future circulatory issues involving the anterior segment.

Table 20.1. Risk factors for the development of anterior segment is­ chemia Advanced age Previous rectus muscles surgery History of vasculopathies (i.e., diabetes and hypertension ) Simultaneous surgery on multiple muscles in the same eye Simultaneous surgery on adjacent rectus muscles Fig. 20.3. Iris hypoperfusion as demonstrated by iris angiography. (Courtesy of Richard A. Saunders, MD)

Surgery on vertical rectus muscles Use of a limbal incision

 

The number of rectus muscles and type (vertical versus horizontal) operated on is another important risk factor for anterior segment ischemia. Surgery on a single vertical muscle in a patient with other risk factors can lead to significant hypoperfusion defects that are detectable with iris angiography and in rare cases to clinically significant anterior segment ischemia. Simultaneous surgery on both vertical rectus muscles carries a higher risk of anterior segment ischemia than simultaneous surgery on the horizontal rectus muscles due to the smaller contribution of the long posterior ciliary arteries to blood flow in the superior and inferior aspects of the anterior segment. Surgery on an adjacent vertical and horizontal rectus muscle is also more likely to lead to an observable negative effect on anterior segment circulation. Detachment of three or four rectus muscles at one time carries a significant risk of compromising the vascular supply of the anterior segment. A history of prior extraocular muscle surgery should be taken into account when weighing the risk of anterior segment ischemia developing if further surgery is planned. As noted earlier, a direct connection between the anterior ciliary arteries that are severed at the time of surgery is never reestablished. Therefore, surgery on other rectus muscles later in life increases the risk of developing anterior segment ischemia. This is especially true if further surgery involves detachment of the third or fourth rectus muscle in the same eye. Repeat surgery on a previously operated rectus muscles does not itself increase the risk of anterior segment ischemia, since reestablishment of blood flow through the previously disrupted anterior ciliary artery does not occur. Underlying vascular disease plays an important role in determining which patients are most at risk for anterior segment ischemia. Patients with co-existent vascular disease in combination with other aforementioned risk factors (advanced age and previous strabismus surgery) are considered at greatest risk for anterior segment ischemia. While strabismus surgery is not contraindicated, surgery must be planned carefully and patients must be counseled appropriately. Surgical strategies designed to reduce the risk of anterior segment ischemia in patients at greater risk should be considered when possible, as reviewed below.

20.4 Signs and Symptoms Anterior segment ischemia can range from mild and selflimiting to severe and vision threatening. Anterior segment is­chemia has been classified into four grades of severity as by Lee and Olver [8] (>Table 20.2). Grade 1 is characterized by reduced iris perfusion that may be demonstrated with iris angiography. Grade 2 is characterized by the presence of pupillary abnormalities such as an ectopic or poorly reactive pupil in the areas of iris hypoperfusion. Grade 3 anterior segment ischemia includes the aforementioned abnormalities and the presence of postoperative uveitis, while grade 4 includes keratopathy that can range from mild to severe. The cornea may develop subtle posterior folds or frank edema (>Fig. 20.4). Grades 1–3 may lead to permanent pupil changes, but do not lead to loss of vi-

20.5  Treatment

205

Table 20.2. Classification of anterior segment ischemia Grade 1

Reduced iris perfusion

Grade 2

Pupillary abnormalities

Grade 3

Postoperative uveitis

Grade 4

Keratopathy (mild to severe)

Fig. 20.4. Striate keratopathy seen in grade 4 anterior segment is­ chemia. (Courtesy of Richard A. Saunders, MD)

sion. Corneal findings in grade 4 anterior segment ischemia include striate keratopathy and corneal edema. The corneal signs may be associated with hypotony, cataract formation and development of a maculopathy. Grade 4 anterior segment is­ chemia can result in loss of vision and even phthisis bulbi in rare cases [9]. Patients with grade 3 or grade 4 anterior segment ischemia may complain of pain and decreased vision, with onset typically 1 or 2 days following surgery. In most cases, improvement will occur in the weeks following surgery. If significant iris ischemia develops, iris atrophy, corectopia and a poorly reactive pupil may remain permanently.

20.5 Treatment There is no universally agreed upon protocol for treatment of anterior segment ischemia [2]. Because the signs of anterior segment ischemia are similar to those seen in more typical uveitis, many ophthalmologists treat empirically with corticosteroids. Mild anterior segment ischemia is generally treated with topical agents and more severe cases are often treated with oral corticosteroids. The use of hyperbaric oxygen was reported by de Smet and co-workers [10] in a patient in whom the use of corticosteroids was contraindicated. This 62-year-old man with thyroid-related eye disease developed anterior segment ischemia after two-muscle adjustable suture surgery of a vertical deviation. He was treated with hyperbaric oxygen and the acute symptoms almost completely resolved in 3 days. Because most patients who develop signs of anterior segment ischemia

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will experience resolution with time, it is difficult to know what role hyperbaric oxygen or other therapies played in the good outcomes reported in such case reports. Animal studies have shown that the use of prostaglandin synthetase inhibitors, such as diclofenac sodium, may have a role in the prevention and/or treatment of anterior segment ischemia [11]. There are no data to suggest that any specific treatment of anterior segment ischemia improves the outcome of this disorder.

20.6 Prevention of Anterior Segment Ischemia The best treatment for anterior segment ischemia is obviously prevention. When possible, a surgical plan for at-risk patients should be designed that will minimize the risk that clinically significant anterior segment ischemia will develop (>Table 20.3). Potential strategies include limiting the number of rectus muscles that are detached from the globe, techniques to preserve anterior ciliary arteries, if possible, and staging surgical procedures, when needed. Each of these strategies are reviewed below.

20.7 Mitigating Risk Through Surgical Planning 20.7.1 Conjunctival incision Limbal conjunctival incisions disrupt the perilimbal conjunctival-Tenon’s circulation. This circulation, though its contribution to anterior segment circulation is modest at best, may provide some protection against development of anterior segment ischemia. Fornix-based incisions result in less disruption to the perilimbal circulation and have been shown to be associated with fewer ischemic changes following three- or fourrectus tenotomies in an animal model [12]. The use of a fornix conjunctival incision might be considered when planning strabismus surgery on patients who are at risk for anterior segment ischemia. The advanced age of patients who are at highest risk for developing anterior segment ischemia, unfortunately, may make the use of a fornix incision difficult with many patients, because of the fragile conjunctiva that is often present in these older patients. Table 20.3. Strategies to prevent anterior segment ischemia Limit the number of rectus muscles that are detached from the globe Preservation of anterior ciliary arteries Staging surgical procedures Utilization of a fornix incision Nonstandard techniques, such as mechanical fixation of the globe

Chapter 20

20.7.2 Minimizing Number of Muscles Operated in an Eye When possible, simultaneous surgery on three rectus muscles in the same eye should be avoided and surgery on all four rectus muscles should only be considered in extremely rare cases when there are no other risk factors for anterior segment ischemia and no other alternatives are available. We have not operated all four rectus muscles simultaneously in an eye and do not advocate doing so. When operating the fourth rectus muscle of a patient who has had previous strabismus surgery or a second or third muscle in a patient who we believe is likely to require more surgery in the future, we will attempt to spare the remaining anterior ciliary arteries by using vessel-sparing techniques for recession surgery and tucks instead of resection surgery. When treatment for a concurrent vertical and horizontal deviation requires surgery on three rectus muscles, consideration should be given to performing surgery on both eyes, if possible. If it is not desirable to perform surgery on both eyes (i.e., due to unilateral vision impairment, patient choice, etc.) consideration should be given to correction of only one component of the deviation. Prism can be attempted for the residual deviation and/or surgery can be offered for the remaining deviation after several months have passed and collateral circulation has developed. Alternative surgical procedures can also be considered. We have used anterior transposition of the inferior oblique mus­ cle in selected cases where a horizontal and vertical deviation requires treatment in a poorly seeing eye [13]. For example, we treated a patient with dense amblyopia who had both a large exotropia and a large hypertropia. A horizontal recession/resection procedure was performed to treat the exotropia. The hypertropia was treated with an anterior transposition of the inferior oblique muscle. The patient’s eyes appeared straight following surgery. The elevation deficit caused by the unilateral inferior oblique procedure was not bothersome to the patient and allowed the vertical deviation to be treated without detaching a third rectus muscle or operating the sound eye. Surgical treatment of paralytic strabismus is probably the most common scenario in which the strabismus surgeon may need to operate on three rectus muscles in an eye simultaneously. Typically, there is a need to perform a transposition procedure to the paralytic muscle, combined with a weakening procedure of the antagonist muscle. In such cases, the surgeon may be able to avoid the need to surgically weaken the antagonist muscle by injecting botulinum toxin into the antagonist. Alternatively, the use of posterior fixation augmentation sutures as described by Foster [14] (Chap. 13) or simultaneous resection of the transposed muscles as described by Brooks et al. [15] (Chap. 13) may eliminate the need for either botulinum injection or surgery on a third rectus muscle. It should be noted that botulinum toxin may not be as effective as surgical weaken­ ing of the antagonist in cases where the antagonist muscle has become significantly contracted over time. These measures are not fully protective and anterior segment ischemia has been reported even when transposition procedures have been combined with the use of botulinum toxin treatment to the antago-

 

nist rectus muscle and following posterior fixation suture augmentation of a transposition procedure [16, 17].

20.7.3 Sparing of the Anterior Ciliary Arteries When surgical correction of strabismus requires operation on multiple rectus muscles, or on the third or fourth muscle of a patient who has undergone previous rectus muscle surgery and who is at risk for anterior segment ischemia, a potentially useful approach is surgical sparing of the anterior ciliary arteries. The anterior ciliary arteries are branches of the ophthalmic artery. They course internal to the rectus muscle and exit the muscle belly before the muscle becomes tendinous. They then travel along the external or orbital surface of the rectus muscles

20.7  Mitigating Risk Through Surgical Planning

before dividing into multiple branches posterior to the muscle insertion. Sparing of one or more anterior ciliary arteries can be accomplished through the use of a muscle splitting procedure, a muscle union procedure, a muscle tucking procedure or by dissecting the ciliary arteries from the muscle (>Fig. 20.5). A partial muscle transposition procedure can be utilized in which the surgeon carefully divides the target muscles, transposing only 50%–80% of the muscle, taking care to leave one anterior ciliary artery from each muscle intact. Coats and coworkers [18] reported successful use of split rectus muscle procedures to treat paralytic strabismus (Chap. 13). If needed at the time of a partial tendon transposition procedure, recession of a third rectus muscle can be done while still only disrupting a minimum number of anterior ciliary arteries. When attempting to spare anterior ciliary vessels in a patient undergoing a split rectus muscle transposition pro-

Fig. 20.5a,b. Examples of surgical options to spare the anterior ciliary arteries. a Dissection of the anterior ciliary arteries and b muscle splitting procedures

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cedure, it is important to evaluate the course of the anterior ciliary arteries on the orbital surface of the muscle/tendon. The arteries often have an irregular and unpredictable course along the muscle. Both arteries are sometimes found on the same side of the muscle, and the arteries can cross from one side of the muscle to the other (>Fig. 20.6). Determining how to best create a longitudinal split in the muscle to preserve the desired artery requires careful consideration of this anatomy followed by careful planning and execution. A Jensen procedure (Chap. 13) is another reasonable alternative to procedures that result in severing of the anterior ciliary arteries when the effect of a transposition procedure is needed. Theoretically, this allows the surgeon to perform a transposition procedure without detaching any of the rectus muscles. However, we believe that suture placement around the rectus muscles during a Jensen procedure results in significant compromise, and usually obliteration, of the circulation in the involved rectus muscles through strangulation of the vessels by the Jensen suture. Anterior segment ischemia has been reported following the Jensen procedure, including one case involving a 10-year-old child [19, 20]. In an effort to minimize disruption of the anterior ciliary arteries following a Jensen procedure, Coats has advocated passing the Jensen suture beneath the anterior ciliary arteries so that only the involved muscles are incorporated in the suture [21] (Chap 13). McKeown has described a surgical technique in which the anterior ciliary arteries are dissected off the surface of the rectus muscle to avoid disruption of the associated anterior ciliary blood flow [22] (>Fig. 20.7). The anterior ciliary arteries are first dissected from the muscle (>Fig. 20.7). Suture is then placed in the muscle near the insertion of the muscle into the sclera and the muscle is then recessed with the anterior ciliary arteries still intact (>Fig. 20.7). Animal studies have demonstrated the sparing of the anterior ciliary artery circulation when multiple rectus muscles are detached from the globe using this technique [23]. The procedure is technically challenging. The technique is not failsafe, and anterior segment ischemia has been reported following strabismus surgery using this technique [24]. Wright has described a modified rectus muscle tucking procedure that appears to preserve the anterior ciliary blood flow, at least in an animal model [24] (>Fig. 20.8). The utility of this procedure in human patients has not been demonstrated, but seems logical. This use of this technique when a rectus muscle resection is needed may be considered when the risk of anterior segment ischemia is thought to be significant.

Chapter 20

Fig. 20.6. The course of the anterior ciliary arteries along the rectus muscles and tendons is highly variable

Fig. 20.7. After dissection of the anterior ciliary arteries from the muscle, the muscle can be recessed, resected, or transposed, leaving the anterior ciliary arteries intact

20.7.4 Mechanical Fixation of the Globe The use of nonstandard techniques such as mechanical fixation of the globe in the primary position using a variety of fixation means is another alternative to achieving alignment of the eyes in the primary position without the need to significantly disrupt the anterior segment circulation. A technique involving the use of periosteum to mechanically fixate the globe in the primary position is described in Chap. 15.

Fig. 20.8. Modified rectus muscle tuck. Note that the anterior ciliary arteries are left undisturbed

 

20.7.5 Staging of Surgery Blood flow to the anterior segment improves over time in most patients following strabismus surgery on the rectus muscles, therefore many surgeons advocate staging surgical procedures when multiple rectus muscles must be operated in the same eye. This approach appears to have value [25]. The amount of time required for collateral circulation to develop following strabismus surgery is unknown, but a few clues are available. Olver and Lee [25] showed that iris circulation recovered within the first 2 weeks following surgery in most patients who did not develop anterior segment ischemia. In patients with grade 3 anterior segment ischemia, blood flow to the iris may not recover for as long as 12 weeks [26]. It is important to reemphasize, however, that the blood flow that is reestablished is inferior to that which was present before surgery. Staging of procedures probably reduces, but does not completely eliminate, the risk of anterior segment ischemia and the condition has been reported in patients undergoing strabismus surgery many years after their initial strabismus operations [26]. Nevertheless, we believe that it is prudent to stage surgery in susceptible patients when surgery is required on more than two rectus muscles in the same eye. Empirically, we wait at least 4 months between operations in this setting, assuming that the patient shows no evidence of anterior segment ischemia after their initial surgery.

20.8 Summary and Recommendations It is impossible to predict with certainty which patients will develop anterior segment ischemia following strabismus surgery. Each patient should be evaluated for the presence of known risk factors. When possible, surgical planning should include a strategy to reduce this risk. Patients at significant risk for anterior segment ischemia should be counseled prior to surgery and monitored for the condition after surgery.

20.8  Summary and Recommendations 6. 7. 8. 9. 10.

11.

12.

13.

14. 15.

16.

17.

18.

19. 20.

21.

References 1.

2.

3.

4.

5.

Wilcox LM, Keough EM, Connolly RJ, Hotte CE (1980) The contribution of blood flow by the anterior ciliary arteries to the anterior segment in the primate eye. Exp Eye Res 30:167–174 France TD, Simon JW (1986) Anterior segment ischemia syndrome following muscle surgery: the AAPO&S experience. J Pediatr Ophthalmol Strabismus 23:87–91 Virdi PS, Hayreh SS (1987) Anterior segment ischemia after recession of various recti. An experimental study. Ophthalmology 94:1258–1271 Chan TK, Rosenbaum AL, Rao R, Schwartz SD, Santiago P, Thayer D (2001) Indocyanine green angiography of the anterior segment in patients undergoing strabismus surgery. Br J Ophthalmol 85:214–218 Hayreh SS, Scott WE (1978) Fluorescein iris angiography. II. Disturbances in iris circulation following strabismus operation on the various recti. Arch Ophthalmol 96:1390–1400

22.

23.

24.

25.

26.

Olver JM, Lee JP (1989) The effects of strabismus surgery on anterior segment circulation. Eye 3 (Pt 3):318–326 Elsas FJ, Witherspoon CD (1987) Anterior segment ischemia after strabismus surgery in a child. Am J Ophthalmol 103:833–834 Lee JP, Olver JM (1990) Anterior segment ischaemia. Eye 4 (Pt 1):1–6 Girard LJ, Beltranena F (1960) Early and late complications of extensive muscle surgery. Arch Ophthalmol 64:576–584 de Smet MD, Carruthers J, Lepawsky M (1987) Anterior segment ischemia treated with hyperbaric oxygen. Can J Ophthalmol 22:381–383 Ino-ue M, Shirabe H, Yamamoto M (1999) Blood-aqueous barrier disruption in experimental anterior segment ischemia in rabbit eyes. Ophthalmic Res 31:213–219 Fishman PH, Repka MX, Green WR, D’Anna SA, Guyton DL (1990) A primate model of anterior segment ischemia after strabismus surgery. The role of the conjunctival circulation. Ophthalmology 97:456–461 Parvataneni M, Olitsky SE (2005) Unilateral anterior transposition and resection of the inferior oblique muscle for the treatment of hypertropia. J Pediatr Ophthalmol Strabismus 42:163–165 Foster RS (1997) Vertical muscle transposition augmented with lateral fixation. J AAPOS 1:20–30 Brooks SE, Olitsky SE, de BRG (2000) Augmented Hummelsheim procedure for paralytic strabismus. J Pediatr Ophthalmol Strabismus 37:189–195; quiz 226–227 Keech RV, Morris RJ, Ruben JB, Scott WE (1990) Anterior segment ischemia following vertical muscle transposition and botulinum toxin injection. Arch Ophthalmol 108:176 Murdock TJ, Kushner BJ (2001) Anterior segment ischemia after surgery on 2 vertical rectus muscles augmented with lateral fixation sutures. J AAPOS 5:323–324 Coats DK, Brady-McCreery KM, Paysse EA (2001) Split rectus muscle modified Foster procedure for paralytic strabismus: a report of 5 cases. Binocul Vis Strabismus Q 16:281–284 von Noorden GK (1976) Anterior segment ischemia following the Jensen procedure. Arch Ophthalmol 94:845–847 Bleik JH, Cherfan GM (1995) Anterior segment ischemia after the Jensen procedure in a 10-year-old patient. Am J Ophthalmol 119:524–525 Kushner BJ, Coats DK, Kodsi SR et al (2002) Grand rounds #68: a case of consecutive exotropia after recession of all four horizontal rectus muscles for the treatment of nystagmus. Binocul Vis Strabismus Q 17:304–311 McKeown CA, Lambert HM, Shore JW (1989) Preservation of the anterior ciliary vessels during extraocular muscle surgery. Ophthalmology 96:498–506 Li Y, Mai G, Wang Z et al (2003) Experimental study on the prevention of anterior segment ischemia by preservation of anterior ciliary vessels. Yan Ke Xue Bao 19:25–32 Wright KW, Lanier AB (1991) Effect of a modified rectus tuck on anterior segment circulation in monkeys. J Pediatr Ophthalmol Strabismus 28:77–81 Olver JM, Lee JP (1992) Recovery of anterior segment circulation after strabismus surgery in adult patients. Ophthalmology 99:305–315 Saunders RA, Sandall GS (1982) Anterior segment ischemia syndrome following rectus muscle transposition. Am J Ophthalmol 93:34–38

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Scleral Perforation and Penetration

Chapter

21

21 Scleral perforation is a known and potentially serious complication of strabismus surgery. It can occur at any time during surgery, but most commonly occurs during reattachment of the muscle to the sclera using sutures. The definition a perfora­ tion and a penetration depends upon the tissue of reference. By definition, a penetrating injury extends only partially through the tissue of reference while a perforation extends through the full thickness of the tissue of reference (>Fig. 21.1). Thus a scleral perforation extends full thickness through the sclera. If the eye wall (including the sclera, choroid, and retina) is the tissue of reference, then a scleral perforation represents only an eye wall penetration. Perforation of the eye wall, therefore, requires passage of a needle through all of the tissues that

constitute the eye wall. Penetration of the sclera occurs in the normal course of strabismus surgery, while perforation of the sclera represents a complication. There is an unsubstantiated, but probably accurate, perception that the incidence of scleral perforation has declined since the evolution of spatula needles in the 1970s. Sprunger and coworkers [1] pointed out that the use of magnification during strabismus surgery has also probably contributed to a decline in the rate of scleral perforation. The reported incidence of scleral perforation varies widely. Simon and coworkers [2] sent questionnaires to 342 members of the American Association for Pediatric Ophthalmology and Strabismus. Scleral perforation, defined in their study as known retinal damage (and therefore requiring full thickness violation

Fig. 21.1. The tissue of reference is important in differentiating a scleral perforation from a scleral penetration. A penetration occurs during the normal course of strabismus surgery and extends only partially

through the sclera, while a perforation extends full thickness through the sclera

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of the sclera), was reported in 728 of almost 554,000 strabismus procedures performed by 223 surgeons responding to the survey. Thus the estimated incidence of scleral perforation was 1.37 for every 1000 strabismus operations performed. While surveys such as this that depend on the surgeon’s memory may over or under estimate the true occurrence of scleral perforation, the study contains some potentially valuable information. Perforations were twice as likely to occur when residents and fellows were operating than when an attending surgeon was operating. Perforations were reported at several stages during surgery. Most occurred during muscle reattachment to the ­sclera with sutures, which accounted for 633 (87%) of the 728 reported perforations. Twenty-four (3.3%) perforations occurred during muscle disinsertion, six (Fig. 21.4). This finding may be

213

Fig. 21.2. Ultrasound biomicroscopy demonstrating a scleral penetration (right), and a scleral perforation (left)

Fig. 21.3. Average depth of needle pass in the sclera of eye bank eyes using four spatulated needles

Fig. 21.4. Relationship between the length of the scleral pass and the depth of the pass in eye bank eyes. Note that there was a trend toward deeper passes as the length of the pass increased, except for the TG100 needle, where the opposite trend was seen

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Chapter 21

Fig. 21.5a,b. Larger needles are more visible as they are passed through the sclera, a feature that may encourage deeper scleral passes. Two needles are shown in the same scleral tunnel: a larger S14 needle, and b smaller S28 needle

related to differences in needle characteristics, including wire diameter, curvature, and length (Chap. 7). The larger S14 needle is more visible as it is passed through the sclera compared with the S28 needle, for example. Figure 21.5 demonstrates the greater visibility of the S14 needle compared with the S28 needle when each is placed in the same scleral tunnel. The ability to visualize the needle as it is passed through the sclera, combined with its shallow curve, may encourage the surgeon to pass larger needles more deeply into the sclera. Likewise, limited ability to see smaller needles during the scleral passes may act to discourage deeper passes.

21.1 Risk Factors Most of the factors that purportedly increase the risk of scleral perforation during strabismus surgery are unproven, though most are intuitive and probably correct. Thin sclera almost certainly increases the risk of scleral perforation. While difficult, if not impossible to prove this in a scientific study, it is logical to believe this is true and the use of extra caution when performing strabismus surgery on patients with thin sclera is advisable. The risk of scleral perforation appears to be greatest during reattachment of a muscle to the sclera, where the needle must carefully penetrate the sclera, but only deep enough to secure the muscle to the globe. The margin of error may be very small in eyes with a thin sclera. Patients who may have thin sclera include, but are not limited to, those with high axial myopia, a history of previous scleritis, and a history of previous ocular surgery. Haugen and Kjeka [8] reported the sudden rupture of the globe in a 78-year-old woman without myopia. During attempts to recess the superior rectus muscle, a large, radial rupture of the sclera occurred with prolapse of a large amount of vitreous. This occurred without undue traction on the globe. Following the rupture, the sclera in this area was noted to be extremely thin. The laceration was repaired, and retinal cryopexy, scleral buckling, and injection of intravitreal gas were performed by a retina surgeon. The patient subsequently developed a blind, painful eye and underwent evisceration.

We experienced rupture of the sclera in one patient, but the setting was quite different than that described by Haugen and Kjeka [8]. We had a patient who experienced a 1-cm rupture of the sclera adjacent to the inferior rectus muscle. Surgery was being performed to recess the inferior rectus muscle in a patient with congenital fibrosis syndrome. The rupture occurred during traction on the globe to expose the muscle, traction that was well in excess of what is required for standard surgery. The intraocular contents did not prolapse and the patient did well with simple closure of the defect. We also experienced rupture of an old scleral cataract incision during surgery on the superior rectus muscle of an elderly man, which was repaired without sequelae. Surgical techniques have been devised to mitigate the risk of scleral perforation in eyes with thin sclera. Rectus muscle recessions and resections can be performed without the need to pass sutures through the sclera, and may be of use in selected patients [9, 10]. Coats and Paysse [9] described a procedure that allows a surgeon to perform a rectus muscle recession or resection without the need to pass sutures through the sclera, greatly reducing the risk of scleral perforation. The technique is outlined below. To perform a rectus muscle recession, two double-arm 6.0 Polyglactin sutures are secured in the rectus muscle, one near its insertion and the other 2 mm posterior to the muscle insertion into the sclera (>Fig. 21.6a). To help minimize bleeding, a hemostat is placed across the muscle between these two sutures and removed after 30–60 s. The muscle between the two sutures is then cut on the crush marks left by the hemostat (>Fig. 21.6b). The suture remaining in the muscle insertion is tied to the suture in the muscle, creating a hang-back recession without the need to penetrate the sclera with a needle (>Fig. 21.6c). To perform a rectus muscle resection, two double-arm 6.0 Polyglactin sutures are secured in the rectus muscle, one near its insertion and a second posteriorly, at the desired resection position (>Fig. 21.7a). The muscle between the two sutures is removed (>Fig. 12.7b) and the two sutures are tied together to bring the resected muscle back to the muscle insertion, without the need to penetrate the sclera with a needle (>Fig. 12.7c).

 

Fig. 21.6a–c. Rectus muscle recession without the need to penetrate the sclera with a needle. a An absorbable suture is secured in the muscle near the insertion and a second suture is placed 2 mm posterior to the insertion. b The muscle between the two sutures is then cut, and c the sutures are tied together to create a hang-back recession

21.1  Risk Factors

Fig. 21.7a–c. Rectus muscle resection without the need to penetrate the sclera with a needle. a An absorbable suture is secured in the muscle near the insertion and a second suture is placed posteriorly in the desired resection position. b The muscle between the two sutures is removed, and c the two sutures are tied together to bring the resected muscle back to the muscle insertion

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In their prospective study of scleral perforation and penetration during resident and fellow surgery, Dang and coworkers [5] found three factors to be statistically associated with eye wall perforations and penetrations. These three factors were younger age, use of the S24 needle, and rectus muscle recession surgery (as opposed to resection surgery). Interestingly, and in contrast to other studies, the skill level and experience of the learner surgeon was not statistically associated with an increase in the rate of scleral perforation and penetration. Dang and co-workers [5] were not able to determine why younger patients were more likely to suffer scleral perforations and penetrations, but postulated that younger patients were more likely to have a standard recession (instead of a hang-back procedure) compared with older patients, or that the sclera might have been less rigid in younger patients, increasingly the propensity toward scleral penetration and perforation. We suggest an alternative explanation may be the fact that exposure of the operative site is typically more difficult in the smaller eyes and orbits of younger children, especially when surgery is performed through a fornix incision. Limited exposure, in our experience, significantly increases the risk of scleral perforation. Other authors have also suggested that scleral perforation occurs more commonly during recession surgery than during resection surgery [3]. This is presumably the result of two factors: (1) the fact that the sclera is thinner behind the insertion where recession sutures frequently must be placed (>Fig. 21.8) and (2) because exposure of the surgical site is more difficult with recession surgery compared to resection surgery. Expo-

Chapter 21

sure is usually excellent at the insertion where resection sutures are placed compared with exposure more posteriorly for a recession, especially a large recession. The use of a hang-back recession technique (Chap. 9) in patients believed to be at higher risk for scleral perforation should be considered. To our knowledge, the report by Dang and coworkers [5] represents the only study to prospectively and statistically demonstrate an increase in the risk of scleral perforation during rectus muscle recession compared with rectus muscle resection surgery. Posterior fixation sutures are generally placed well behind the limbus, where surgical exposure can be difficult. Alio and Faci [11] evaluated 187 eyes by indirect ophthalmoscopy following placement of posterior fixation sutures and followed abnormal eyes over time. While they did not detect any retinal perforations, they did detect fundus abnormalities in 29 (15.5%) of these 187 eyes. The lesions primarily consisted of chorioretinal scars, though a triangular-shaped area of choroidal ischemia was noted in one patient (>Fig. 21.9). These authors hypothesized to that ophthalmoscopically visible fundus changes might be more common following the poster fixation sutures technique because the technique itself is difficult and/or because the lesions are easier to visualize than lesions that might occur more anteriorly during routine strabismus surgery. A technique reported by Clark and coworkers [12, 13] involving placement of a nonabsorbable suture in the medial rectus muscle and its associated pulley may be considered in order to minimize or eliminate the risk of scleral perforation for appropriate patients (>Fig. 21.10).

Fig. 21.8. Scleral perforation may be more likely to occur during recession surgery because the sclera is very thin behind the muscle insertion where sutures often must be placed in the sclera during surgery. The gray area represents the area of thin sclera behind the insertion

Fig. 21.9. Fundus lesions noted 3 months after posterior fixation suture surgery. {Reprinted from Alio JL, Faci A (1984) Fundus changes following faden operation. Arch Ophthalmol 102:211–213 [11], with permission. Copyright © (1984) American Medical Association. All rights reserved}

 

21.2  Clinical Evidence of Perforation

Fig. 21.10. Posterior fixation suture technique involving suturing the medial rectus muscle to its associated pulley using a nonabsorbable suture. The pulley is hooked with a small hook (right) and a suture passed through the pulley to secure it to the muscle (left). (Courtesy of Robert Clark, MD)

21.2 Clinical Evidence of Perforation Scleral perforation probably goes unrecognized in many cases. We have occasionally been surprised to find evidence of a scleral perforation that was not suspected at the time of surgery, but detected on indirect ophthalmoscopy immediately after surgery (>Fig. 21.11) or through detection of a chorioretinal scar in the area of muscle reattachment in the late postoperative period. Intraoperative signs of a scleral perforation may vary depending on the patient and the severity of the perforation, but in general we have noted that one or more of the following usually occurs during recognized scleral perforation. First, the experienced and even the inexperienced surgeon often feels a “gestalt” that the needle pass was too deep and is immediately suspicious that a perforation may have occurred. Recognized scleral perforations are often heralded by small piece of uveal or a bead of vitreous on the tip of the suture needle [14]. A small amount of dark red, deoxygenated blood from the choroidal circulation may be seen following a scleral perforation, but external bleeding is generally very mild when it occurs. If a retinal perforation has occurred, liquid vitreous may be seen exiting from either the scleral entrance or exit wound, though it is more commonly seen at the exit wound. We operated on an elderly woman who suffered a 5-mm scleral laceration during a Harada–Ito procedure while the superior oblique tendon was being sutured to the sclera above the lateral rectus muscle. Vitreous was seen to extend through the scleral laceration. The vitreous was excised and the scleral laceration was closed with 6.0 Polyglactin suture. Interestingly, examination of the retina underlying the site of the laceration failed to demonstrate the presence of a retinal break, underscoring the fact that scleral perforation can easily go undetected during postoperative evaluation of the retina. The patient recovered without sequelae. Finally, even without obvious loss of blood or fluid from the eye, the globe may become softer immediately following a scleral perforation.

Indirect ophthalmoscopy to inspect the retina underlying the surgical site should be performed when a scleral perforation is suspected. We generally administer dilating drops as soon as a perforation is suspected and perform indirect ophthalmoscopy at the conclusion of the surgery. Some surgeons, including us, place neosynephrine drops into the eyes of strabismus patients prior to surgery to produce vasoconstriction of the conjunctival blood vessels during surgery and this often results in sufficient papillary dilation that further dilation of the pupil may not be needed to inspect the retina. If a perforation is suspected, the suture is withdrawn and replaced in an alternative location before proceeding with surgery. Even when a perforation is present, there may be no obvious sign of perforation during indirect ophthalmoscopy, thus we reposition the suture before inspecting the retina for evidence of perforation. If a retinal break is detected, treatment is initiated as discussed below in Sect. 21.3.

Fig. 21.11. Retinal perforation seen immediately after strabismus surgery. Note the absence of associated hemorrhage. In this case, the perforation was obvious at the time it occurred

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In a study of eye wall perforations in rabbit eyes, Sprunger and coworkers [1] were unable to verify the site of a known ­scleral perforation in three of four rabbit eyes in which a needle had been “thrust into the eye and removed,” despite knowing both that a perforation had occurred and its exact location. Inability to identify the site of a retinal break may be less likely in cases of human retinal breaks occurring during surgery where the perforation is more likely to have been oblique to the retina, resulting in greater disruption of intraocular structures compared to a needle that has been thrust directly into the eye, as was done in the aforementioned study. While hemorrhages in an experimental setting have been reported to be small [1], large preretinal hemorrhages have been reported. All five patients experiencing retinal perforation at the time of muscle reattachment reported by Awad and coworkers [4] had evidence of retinal perforation, including localized vitreous hemorrhage noted at the time of intraoperative fundus examination.

21.3 Potential Sequelae of Scleral and Eye Wall Perforation 21.3.1 Retinal Detachment Retinal detachment has been reported as a complication of both incisional strabismus surgery and from inadvertent intraocular injection of botulinum toxin to treat strabismus. Liu and coworkers [15] reported a patient who was noted to have a retinal tear and a bullous retinal detachment following botulinum injection in which inadvertent eye wall perforation occurred. The detachment spontaneously resolved and the patient was treated with prophylactic laser retinopexy. Awad and coworkers [4] reported a patient who underwent a medial rectus muscle recession who suffered a 4×3 mm defect in the sclera during disinsertion of the muscle. The defect was closed with a scleral patch graft and the medial rectus muscle was reattached posterior to the patch graft. The patient subsequently developed a vitreous hemorrhage and a retinal detachment, requiring a pars plana vitrectomy and gas–fluid exchange with endolaser. The final visual acuity at 68 months following surgery was 20/50, two lines worse than the preoperative visual acuity. The child had high myopia with a refractive error of ­–8.50 diopters and a thin sclera, which was thought to have predisposed the child to this complication. Wolf and coworkers [16] reported the development of anterior segment ischemia and retinal detachment due to an unsuspected perforation that occurred during vertical rectus muscle surgery. The patient’s vision at the time of the report was 20/400 due to a cataract. The fact that scleral perforation can occur and can go unrecognized is highlighted by reports of retinal detachment following strabismus surgery in patients in whom a perforation of the global was not suspected intraoperatively [17]. Retinal cryopexy has often been recommended as a prophylactic measure in the event of an eye wall perforation [17]. However, retinal cryopexy, a procedure known to disrupt the blood–retinal barrier, has been shown to stimulate development of traction

Chapter 21

retinal detachment in eyes with an ocular wound in an experimental setting through development of epiretinal membranes [18]. A common intraocular finding in many cases of strabismus surgery that led to retinal detachment was the presence of later developing fibrous tissue emanating from the perforation site and extending into the vitreous [17, 19]. Retinal detachment may occur months to years after surgery [19]. Mittleman and Bakos [20] found that the incidence of retinal detachment was higher if the sclera over a perforation site had been treated with heavy retinal cryotherapy, in a study they performed on rabbit eyes. This complication was less likely to occur if only mild cryotherapy was administered [21]. These authors suggested that unless significant vitreous hemorrhage was present or the patient had a predisposing risk factor for retinal detachment, that prophylactic treatment to prevent a retinal detachment was probably not warranted. This has also been our experience and our general recommendation. The purpose of retinal cryotherapy or laser retinopexy is to stimulate adjacent retinal pigment epithelial cells so that a scar develops between the retina and retinal pigment epithelium, thus closing the retinal break and preventing access of liquid vitreous to the subretinal space, which can result in a progressive retinal detachment. It has been our belief that direct stimulation of the retinal pigment epithelium with a surgical needle during unintentional eye wall perforation provides enough stimulation of the retinal pigmented epithelium to initiate this process, and that administration of prophylactic measures may produce more harm than benefit in many cases. Sprunger and coworkers [1] demonstrated using a rabbit retinal perforation model that cryotherapy often resulted in the release of pigmented cells into the vitreous, whereas laser retinopexy did not (>Fig. 21.12). They were concerned that these released pigment cells had the potential to stimulate contraction of the vitreous, leading to distortion of retinal anatomy. They suggested that observation alone or laser retinopexy were reasonable options if a retinal perforation occurred during surgery. We agree with this philosophy, and do not generally recommend prophylactic laser retinopexy if a small retinal break without associated retinal fluid is seen. On the other hand, if a large retinal break is seen, especially if associated with subretinal fluid, we will apply a double row of laser retinopexy to surround the break in an attempt to reduce the risk of progressive retinal detachment, though we recognize that there is no sound scientific evidence available to support this position. For patients with a high risk for retinal detachment, such as patients with high axial myopia and aphakia, we have a lower threshold for recommending prophylactic laser retinopexy. We do not recommend use of prophylactic cryotherapy in any setting.

21.4

Vitreous and Anterior Chamber Hemorrhage

Vitreous hemorrhage can occur as a result of eye wall perforation during strabismus surgery. Vitreous hemorrhage is generally mild and localized [1, 4], though it can be more pro-

 

nounced [14] and late onset of severe hemorrhage thought to be related to previous strabismus surgery has been reported [19]. Arnold and coworkers [22] reported a patient who experienced a scleral-choroidal perforation who suffered vitreous hemorrhage during and after strabismus surgery. The perforation was felt to have been caused by altered surgical conditions related to the patient’s asymptomatic and unrecognized rigid cervical spine. The patient’s head did not make contact

21.7  Prevention

with the operating table and was noted to shift up and down by several centimeters when the patient coughed during surgery. Vitrectomy and intraocular lens implantation was required to restore the patient’s vision and binocularity. Anterior chamber hyphema has been reported as a consequence of perforation of the eye wall when placing traction sutures near the limbus [4].

21.5 Endophthalmitis Endophthalmitis [23] and even phthisis bulbi [24] can occur as a consequence of scleral perforation during strabismus surgery. Some authors have argued that scleral perforation must have occurred if endophthalmitis develops. The lack of recognition of scleral perforation in patients who have developed a retinal detachment after strabismus surgery has been cited as supportive of the fact that scleral perforation can go unrecognized [17, 19] and therefore was most likely present in patients who develop endophthalmitis despite lack of recognition of a perforation. Parks [25] believed that endophthalmitis could occur as a result of postoperative cellulites over the operative site and routinely recommended a 5-day course of oral antibiotics after strabismus surgery. We do not believe that scleral perforation is a prerequisite for endophthalmitis; instead believing that penetration of the sclera alone, especially deep penetration, may be sufficient to allow access of microbes into the eye. Endophthalmitis is discussed in detail in Chap. 22.

21.6 Anterior Chamber Perforation The fact that a perforation of the eye can occur at any time during strabismus surgery has been stressed. Even seemingly simple surgical maneuvers, such as the passage of traction sutures, can result in penetration of the eye wall [2, 4]. We once had the unfortunate experience of passing a conjunctival closure suture through the cornea and into the anterior chamber during the simple process of suture closure of a limbal incision. No further complications developed and the patient did well, but the potential for a more serious problem was certainly recog­nized. Awad and coworkers [4] reported four patients who experienced collapse of the anterior chamber and hyphema following placement of traction sutures at the limbus. They abandoned surgery on these patients until the hyphema had cleared. The patients underwent uneventful strabismus surgery at a later date. None of the patients experienced a loss of best-corrected visual acuity, or developed cataract, glaucoma, or other anterior segment complications. Fig. 21.12a,b. Histopathology of retinal break in a rabbit eye induced by eye wall perforation. a Dispersion of pigmented cells is seen in the vitreous of cryo-treated eyes, but not in b laser-treated, or in untreated eyes (not shown). (Reprinted with permission from Sprunger DT, and coworkers. Management of experimental globe perforation during strabismus surgery. J Pediatr Ophthalmol and Strabismus 1996; 33:140–143. Copyright © 1996, Slack, Inc.)

21.7 Prevention Careful surgical planning and technique are both important in preventing scleral and eye wall perforation during strabismus surgery. Assuring adequate surgical exposure, taking

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Scleral Perforation and Penetration

special precautions on patients with thin sclera, and selection of a spatulated needle that is appropriate for the specific surgical task required are the major methods available to reduce the risk of perforation. Perforations are less likely to occur as a surgeon gains experience. The surgeon should avoid the tendency to believe that scleral perforation only occurs during muscle reattachment to the globe, but instead should be vigilant throughout the procedure, because scleral perforation can occur at virtually any time during surgery. For patients who are at particularly high risk for scleral perforation, such as patients with high myopia, or for monocular patients undergoing strabismus surgery on their sound eye, techniques that allow strabismus surgery to be performed without the need to penetrate the sclera with a needle should be considered (>Figs. 21.6, 21.7). Methods to reattach muscles to the sclera with adhesives have been studied, but are not yet a viable tool for use in strabismus surgery.

21.8 Treatment Most scleral perforations are small, even microscopic. Lacerations of the sclera and even unintentional block resections of the sclera can occur during strabismus surgery and the surgeon must be prepared to manage this complication or have ready access to a consultant surgeon. Awad and coworkers [4] reported placement of a scleral patch graft at the time of strabismus surgery to repair a large scleral defect with uveal prolapse that occurred during muscle detachment in a patient with high myopia. We believe that retinal cryopexy should be avoided. If a large retinal tear is noted, or if a small retinal tear is noted in a patient at high risk for retinal detachment, laser retinopexy may be a reasonable consideration. Laser can be applied in two rows to surround the retinal break and the patient should be following closely during the postoperative period for evidence of endophthalmitis and/or retinal detachment. In addition to measures to identify and manage a retinal break, our general practice when a perforation is suspected is to withdraw the needle and suture and reposition it in an alternative location. We do this because of available evidence which demonstrates not only that needles and sutures used during strabismus surgery are commonly contaminated during surgery [26, 27], but also experimental evidence that contaminated needles are capable of transferring live bacteria into the eye during experimental eye wall perforation [28]. We empirically apply antibiotic drops and/or 5% povodine-iodine solution to the operative site if a perforation has occurred or is strongly suspected. We will consider administration of subconjunctival antibiotics and often administer a dose of intravenous antibiotics and/or prescribe prophylactic oral antibiotics postoperatively. Though recognizing that this protocol has not been scientifically validated or shown to be necessary, we wish to make every effort possible to reduce the risk of endophthalmitis, though we have no quarrel with the surgeon who chooses an alternate approach. Probably the most important step to take after a scleral perforation has been identified is to inform and educate the pa-

Chapter 21

tient and/or family so that they are aware of the potential for a serious complication and understand the signs and symptoms of endophthalmitis and retinal detachment in the rare event that one of these complications occurs. We follow patients with known scleral perforations more frequently then routine postoperative patients, usually seeing them on postoperative days 1, 3, and 7, and as guided by examination findings and our level of concern. It is our practice to dilate the pupil and examine the retina at each of these early postoperative visits.

References 1.

2.

3.

4.

5.

6. 7. 8.

9. 10. 11. 12.

13.

14.

15.

16.

Sprunger DT, Klapper SR, Bonnin JM, Minturn JT (1996) Management of experimental globe perforation during strabismus surgery. J Pediatr Ophthalmol Strabismus 33:140–143 Simon JW, Lininger LL, Scheraga JL (1992) Recognized scleral perforation during eye muscle surgery: incidence and sequelae. J Pediatr Ophthalmol Strabismus 29:273–275 Morris RJ, Rosen PH, Fells P (1990) Incidence of inadvertent globe perforation during strabismus surgery. Br J Ophthalmol 74:490–493 Awad AH, Mullaney PB, Al-Hazmi A et al (2000) Recognized globe perforation during strabismus surgery: incidence, risk factors, and sequelae. J AAPOS 4:150–153 Dang Y, Racu C, Isenberg SJ (2004) Scleral penetrations and perforations in strabismus surgery and associated risk factors. J AAPOS 8:325–331 Goldstein JH, Prepas SB, Conrad SD (1982) Effect of needle characteristics in strabismus surgery. Arch Ophthalmol 100:617–618 Helveston EM (1993) Surgical management of strabismus: an atlas of strabismus surgery, 4th edn. Mosby, St Louis., Mo., p 119 Haugen OH, Kjeka O (2005) Localized, extreme scleral thinning causing globe rupture during strabismus surgery. J AAPOS 9:595–596 Coats DK, Paysse EA (1998) Rectus muscle recession and resection without scleral sutures. J AAPOS 2:230–233 von Noorden GK (1982) Muscle surgery without scleral sutures. Ophthalmic Surg 13:113–114 Alio JL, Faci A (1984) Fundus changes following faden operation. Arch Ophthalmol 102:211–213 Clark RA, Ariyasu R, Demer JL (2004) Medial rectus pulley posterior fixation: a novel technique to augment recession. J AAPOS 8:451–456 Clark RA, Ariyasu R, Demer JL (2004) Medial rectus pulley posterior fixation is as effective as scleral posterior fixation for acquired esotropia with a high AC/A ratio. Am J Ophthalmol 137:1026–1033 Greenberg DR, Ellenhorn NL, Chapman LI, Miller MT, Folk ER (1988) Posterior chamber hemorrhage during strabismus surgery. Am J Ophthalmol 106:634–635 Liu M, Lee HC, Hertle RW, Ho AC (2004) Retinal detachment from inadvertent intraocular injection of botulinum toxin A. Am J Ophthalmol 137:201–202 Wolf E, Wagner RS, Zarbin MA (2000) Anterior segment is­ chemia and retinal detachment after vertical rectus muscle surgery. Eur J Ophthalmol 10:82–87

  17. Gottlieb F, Castro JL (1970) Perforation of the globe during strabismus surgery. Arch Ophthalmol 84:151–157 18. Campochiaro PA, Gaskin HC, Vinores SA (1987) Retinal cryopexy stimulates traction retinal detachment formation in the presence of an ocular wound. Arch Ophthalmol 105:1567–1570 19. Basmadjian G, Labelle P, Dumas J (1975) Retinal detachment after strabismus surgery. Am J Ophthalmol 79:305–309 20. Mittelman D, Bakos IM (1984) The role of retinal cryopexy in the management of experimental perforation of the eye during strabismus surgery. J Pediatr Ophthalmol Strabismus 21:186–189 21. Taherian K, Sharma P, Prakash P, Azad R (2004) Scleral perforations in strabismus surgery: incidence and role of prophylactic cryotherapy – a clinical and experimental study. Strabismus 12:17–25 22. Arnold RW, Barnett M, Limstrom SA, Swanson D (2001) Vision loss associated with a stiff neck complicating strabismus surgery. Binocul Vis Strabismus Q 16:181–186 23. Salamon SM, Friberg TR, Luxenberg MN (1982) Endophthalmitis after strabismus surgery. Am J Ophthalmol 93:39–41

References 24. Apple DJ, Jones GR, Reidy JJ, Loftfield K (1985) Ocular perforation and phthisis bulbi secondary to strabismus surgery. J Pediatr Ophthalmol Strabismus 22:184–187 25. Parks MM (1989) Routine antibiotic coverage in eye muscle surgery [letter]. Binocular Vision Q 4:152–153 26. Olitsky SE, Vilardo M, Awner S, Reynolds JD (1998) Needle sterility during strabismus surgery. J AAPOS 2:151–152 27. Carothers TS, Coats DK, McCreery KM et al (2003) Quantification of incidental needle and suture contamination during strabismus surgery. Binocul Vis Strabismus Q 18:75–79 28. Wang N, Coats DK, Paysse EA, Saunders RA, Wilson P, Rossman SN (2000) The significance of cryotherapy in reducing bacterial count during experimental scleral perforation. In: de Farber JT (ed) European Strabismology Association. Swets and Zeitlinger, Barcelona, pp 177–180 29. Noel LP, Bloom JN, Clarke WN, Bawazeer A (1997) Retinal perforation in strabismus surgery. J Pediatr Ophthalmol Strabismus 34:115–117

221

Chapter

Postoperative Infection

22

22 Serious infections following strabismus surgery are uncommon. Most busy strabismus surgeons are unlikely to see more than one or two cases of endophthalmitis and/or orbital cellulitis during their entire career. Other important, but less serious infections, such as preseptal cellulitis and subconjunctival abscesses, are more common. Endophthalmitis is so rare ­after strabismus surgery that it is often initially misdiagnosed. Though it is uncommon, the visual outcome of endophthalmitis following strabismus surgery is often poor, and this could in part be compounded by a delay in diagnosis. Thus, surgeon awareness of risk factors, clinical presentation, and treatment remain important. A comprehensive review of ocular, periocular, and systemic infection as related to strabismus surgery is presented in this chapter.

22.1 Risk Factors The most common source of viable organisms producing endophthalmitis after strabismus surgery is not known. Potential sources of infection include the normal bacterial flora in the region of the operative site, contaminated surgical material, postoperative periocular abscess, and transient endogenous bacteremia. There are many proven and suspected factors that predispose a patient to postoperative infection. Patients who are immunocompromised, such as those with poorly controlled diabetes, patients undergoing chemotherapy, and patients on corticosteroid therapy, are at increased risk for postoperative infection due to their lack of ability to mount a normal immune response to deal with the inevitable contamination of the operative site that occurs during the normal course of surgery. Most of the available data on risk factors for surgical site contamination and for risk of endophthalmitis following ophthalmologic surgery relate to cataract surgery and other intraocular surgical procedures. Though uncomplicated strabismus surgery does not result in perforation of the sclera, the strabismus surgeon should still be aware of these reports. One study suggested that an ophthalmic surgeon’s speaking to a patient during surgery, especially if the patient was hard of hearing requiring the surgeon to shout to be understood, could increase the risk of bacterial contamination of the operative site [1].

22.1.1 Glove Perforation The surgeon’s hands are an important potential source of bacterial contamination during surgery and proper hand washing prior to surgery is important in reducing the risk of contamination of the operative site from this source. Glove perforation during surgery occurs more frequently than surgeons may ­realize and glove perforation not only exposes the patient to contaminants on the surgeon’s hands but also exposes the surgeon to potentially infected patient tissues and body fluids. Most ophthalmic surgeons erroneously believe that holes seldom develop in their own gloves during surgery [2]. One study of 2292 surgical procedures of all types identified glove tears in 249 (11%) gloves from surgeons, assistants, and/or nurses [3]. The mechanism of glove tears was identified in only a third of the cases, thus occult glove perforation is more common than recognized perforation. The rate of glove perforation in ophthalmologic surgery has been reported to be as high as 4% [4]. Perforation was most common with retina surgery and least common with strabismus surgery. Perforation of the surgeon’s left glove was more common than perforation of right gloves. The risk appeared highest for perforation of left gloves while handling suture needles. Sutures should be loaded onto the needle holder without ever touching the needle itself. Placement of a needle into a needle holder can be easily facilitated by holding the suture material close to the needle. Holding the needle in one’s hand while placing it into the needle holder or passing it off the operative field is a common, but very poor, practice. It exposes both the patient and operating room personnel to unnecessary risk.

22.1.2 Operating Room Equipment and Supplies Operating room equipment and supplies are generally sterile and are rarely the source of contamination that results in postoperative infection. However, bacterial contamination of solutions that are used during intraocular surgery have been reported as the source of organisms leading to the development of endophthalmitis [5]. Though we are not aware of any cases

224

Postoperative Infection

of endophthalmitis due to contaminated solutions used during strabismus surgery and recognize that this mechanism of contamination is less likely to occur during strabismus surgery compared with intraocular surgery, serious infection through contaminated solutions is possible. Instruments, implants, explants, and surgical supplies can become contaminated during any surgical procedure through several potential mechanisms. The ocular adnexa and conjunctiva of the patient are prime sources of potential contamination during ophthalmologic surgery. Doyle and coworkers [6] reported significant contamination of intraocular lenses that touched the bulbar conjunctiva of the patient during cataract surgery or that were left on the surgical drape near the operative site. Though most of the available data relate to intraocular surgery, similar mechanisms of contamination are possible during strabismus surgery. Olitsky and coworkers [7] studied the rate of needle contamination during strabismus surgery in patients who had received preoperative skin and conjunctival preparation with standard 5% povidone-iodine solution prior to surgery. They were able to demonstrate bacterial contamination on 16 (15.1%) of 106 needles and 15 (24.6%) of 61 cases of strabismus surgery. The organisms recovered closely resembled indigenous bacterial flora. They believed that needles used during strabismus surgery could be a source of bacteria that could lead to infection after strabismus surgery. Carothers and coworkers [8] reported on the level of bacterial contamination of both needles and sutures used during strabismus surgery. They cultured needles and sutures used on 56 eyes from 31 consecutive children undergoing strabismus surgery. The cases had received preoperative preparation with a standard solution of 5% povidone-iodine including instillation in the conjunctival fornices. Of the 31 cases, 17 (54.8%) produced at least one positive specimen. It was found that 19% of the needles and 25.2% of the sutures were culture positive. Most of the positive specimens (96.7% of needles, 91.3% of sutures) produced three or fewer colony forming units, corresponding to seven or fewer total viable organisms per needle or suture in accordance with the dilution scheme, and coagulase-negative staphylococci overwhelmingly predominated. While most of the contaminated needles and sutures were not heavily contaminated, some were sufficiently contaminated with enough colony forming units of bacteria that they were probably capable of producing endophthalmitis under the right circumstances. Wang and coworkers [9] have demonstrated that needles and sutures contaminated with a physiologic dose of bacteria can transmit live bacteria into an eye bank eye during eye wall perforation. Given the fact that the sutures and needles used during surgery have a high potential to become contaminated with bacteria during routine strabismus surgery, steps to reduce the risk of exposure to contaminated needles and sutures should be considered. Isolation of the eyelids and lashes with an adhesive drape (>Fig. 22.1) may reduce the potential for contamination during ophthalmic surgery, though there is no evidence that this measure reduces the risk of infection related to strabismus surgery. If a scleral perforation is suspected or confirmed during surgery, the surgeon should consider halting passage of the needle and withdraw it immediately, before potentially con-

Chapter 22

Fig. 22.1. Isolation of the lashes for strabismus surgery to reduce the risk of contamination of instruments and supplies

taminated suture material is drawn through the perforation site. Likewise, if the needle has already been passed through the sclera, it may be prudent to cut the suture flush with the sclera and remove it, to avoid having to draw additional potentially contaminated needle and suture back through the suspected perforation site to remove it. Leaving a foreign body (suture) in a scleral perforation site has the potential to increase the risk of infection, and thus repositioning of the suture to another site should be considered mandatory.

22.2 Endophthalmitis The estimated incidence of endophthalmitis following strabismus surgery ranges from 1 in 350,000 cases [10] suggested in 1962 to 1 in 18,500 cases [11] suggested in 1992. Numerous risk factors have been proposed. Scleral perforation is commonly believed to increase the risk of developing endophthalmitis following strabismus surgery, though clear evidence that this is the case is not available. Salamon and coworkers [12] treated two cases of endophthalmitis following strabismus surgery. Scleral perforation was recognized during surgery on one patient and was treated with cryopexy. Sclera perforation was suspected, but not confirmed, in the second case. Recchia and coworkers [13] reported six cases of endophthalmitis in children following strabismus surgery who were referred to them over a 5-year period. Scleral perforation was not suspected by the operating surgeon at the time of strabismus surgery in these six cases. The cause of endophthalmitis after strabismus surgery is not known, and is probably variable. Several theories have been proposed. Rosenbaum [14] suggested the possibility that endophthalmitis following strabismus surgery could have an endogenous origin. Good and coworkers [15] suggested that partial obstruction of the nasolacrimal duct and upper airway infection could be a risk factor for development of postoperative endophthalmitis in children undergoing cataract surgery. There is no reason to doubt that these same factors might not

 

also increase the risk of endophthalmitis following strabismus surgery. Staphylococcus and Streptococcus have been the predominant organisms cultured in reported cases of endophthalmitis (>Table 22.1). Abscess formation occurring around the muscle suture in the absence of sclera perforation was suspected in one reported case [14]. Kushner and Meyers [16] reported a case of endophthalmitis following strabismus surgery reoperation that was caused by Staphylococcus aureus. Perforation was not suspected at the time of surgery. The child went swimming 5 days after surgery and 2 days later complained of right eye discomfort and erythema of the conjunctiva was noted by the parents. These authors felt that swimming was the likely source of exposure to the infectious agent. Recchia and co-workers [13] noted that five of the six cases of the endophthalmitis they treated occurred following surgery on the left medial rectus muscle. They postulated that surgery by a right-handed surgeon in the tight surgical space afforded during medial rectus muscle surgery through a fornix incision could have played a role in increasing the risk of infection. The insidious presentation of endophthalmitis following strabismus surgery and the tendency for children not to complain of unilateral vision loss both make this already rare condition even more difficult to accurately diagnose. An accurate diagnosis of endophthalmitis is often not made until several days after the onset of signs and/or symptoms (>Table 22.1). Reported signs and symptoms are numerous. The most common presenting complaints have been pain, eyelid swelling, and redness. Table 22.2 presents a comprehensive tabulation of the signs and symptoms reported in 22 cases of endophthalmitis. Onset of symptoms has been reported as early as 1 day after surgery to as long as 13 days after surgery (>Table 22.1). Diagnosis has been reported as early as 3 days after surgery and as late as 30 days following surgery. Thus, no reasonable follow-up schedule can ensure that the surgeon will be able to make an early diagnosis of endophthalmitis in all patients. The use of antibiotic drops following surgery is not necessarily protective either. In the largest series of reported cases, the six patients reported by Recchia and co-workers [13], postoperative management had included a combination antibiotic steroid drop in all cases. The visual outcome following most reported cases of endophthalmitis following strabismus surgery has generally been poor, with rare exceptions. Among the 22 cases reviewed in Table 22.1, the outcome was light perception or worse in 12 cases with 6 eyes requiring enucleation and 3 eyes developing phthisis bulbi. Occasionally favorable outcomes have been reported. Uniat and coworkers [17] reported a successful outcome in a 78-year-old woman who developed endophthalmitis due to Staphylococcus epidermidis in association with a scleral perforation during surgery. The onset of symptoms and diagnosis occurred on the third postoperative day and the patient underwent vitrectomy with intravitreal antibiotics. Kushner and Meyers [16] also reported a patient who underwent strabismus surgery on an amblyopic eye and who was diagnosed with endophthalmitis due to Staphylococcus aureus 8 days after surgery. The patient underwent pars plana vitrectomy with intravitreal and subconjunctival antibiotic administration. This

22.2  Endophthalmitis

child had hand motion vision at the time of diagnosis but ultimately recovered to 20/40, the level of vision present prior to strabismus surgery. Walton and Cohen [18] reported successful treatment of endophthalmitis due to Staphylococcus epider­ midis with intravitreal antibiotics and corticosteroids. The Endophthalmitis Vitrectomy Study [19] provided guidelines regarding the use of intravitreal antibiotics and vitrectomy in patients with frank endophthalmitis following cataract surgery. Although translating these results to noncataract surgery-related cases of endophthalmitis may be controversial, the recommendations of the Endophthalmitis Vitrectomy Study probably have some application to endophthalmitis after strabismus surgery. The study demonstrated that if vision was light perception or worse, a pars plana vitrectomy with intravitreal administration of antibiotics was the treatment of choice. On the other hand, if vision was hand motion or better an intravitreal injection of antibiotics alone was appropriate. An intravitreal antibiotic regimen commonly used includes ceftazidime (2.25 µg/ml) and vancomycin (1 µg/ml) in an adult eye. While systemic treatment alone is insufficient, fourth generation fluoroquinolones may be an adjunct to maintain adequate intravitreal levels of antibiotics following intravitreal antibiotic administration. Most strabismus surgery is performed on children, therefore special considerations for the treatment of endophthalmitis in children require clarification. First, assessment of vision in infants and young children may be impossible, rendering application of the Endophthalmitis Vitrectomy Study recommendations even more difficult. Second, the safety of systemic use of fourth generation fluoroquinolones in children is unclear. We will use these agents in children in consultation with an infectious disease specialist when indicated. It should be stressed that visual outcomes from endophthalmitis following strabismus surgery are often poor. Endophthalmitis after strabismus surgery is rare and there is a complete absence of clinical trials to provide evidence-based science on how to manage patients with this complication. Although the Endophthalmitis Vitrectomy Study may provide some useful guidelines, the population studied did not include patients with endophthalmitis following strabismus surgery. Despite its infrequency, the poor visual outcome commonly associated with endophthalmitis after strabismus surgery justifies preventative measures. Prevention of all cases of endophthalmitis following strabismus surgery is probably not feasible. Rosenbaum [14] suggested that “minor” preoperative infections, which are often considered unimportant by operating surgeons, might need to be reevaluated. The frequency of upper respiratory tract infection or other minor infection in children at the time of strabismus surgery is high and it would be difficult, if not impossible, to demonstrate an association between ocular infection following surgery and the presence of such “minor” infection at the time of surgery. Concurrent systemic infection was not reported in the majority of cases of endophthalmitis reported in the literature. The protective value of topical antibiotics following strabismus surgery is controversial. Kearns and Cullen [20] randomized 104 children undergoing strabismus surgery to one of 3 postoperative treatment regimens: (1) fucithalmic twice a day,

225

1982

1988

1989

1990

1993

1995

2000

2000

2000

2000

2000

2000

2000

2004

2005

Uniat et al. [17]

Kushner and Meyers [16]

Bialasiewicz et al. [44]

Thomas et al. [45]

Kivlin and Wilson [28]

Recchia et al. [13]

Recchia et al. [13]

Recchia et al. [13]

Recchia et al. [13]

Recchia et al. [13]

Recchia et al. [13]

Thorne and Maguire [46]

Walton and Cohen [18]

Ruby et al. [47]

1982

Salamon et al. [12]

1985

1979

Weinstein et al. [42]

Salamon et al. [12]

1975

McNeer [41]

Apple et al. [43]

1970

Gottlieb and Castro [40]

0.6

72.0

4.0

4.0

6.0

0.6

1.5

0.6

3.0

6.0

OS

OS

OD

OS

OS

OD

OS

OS

OS

OD

OD

OD

OS

OD

OS

OD

OS

OS

OD

Eye

IV, Ivit

8

2

IV, Ivit

6

3

IV, Ivit

7

IV, Ivit

IV, Top

7

IV, Ivit

Ivit, SC, Top

5

5

IV

3

IV, SupC, SC

Ivit, SC, PO, Top

4

3 14

IV, Ivit

4

5

IV, Ivit

4

4

Enucleated Phthisis Enucleated Phthisis Phthisis Retinal detachment/Poor 20/40–2 (amblyopia) NLP

St. pneumoniae No growth S. aureus H. influenzae St. pneumoniae H. aegyptius S. epidermidis St. pneumoniae

PPV PPV, PPL, Cryo PPV, PPL

T&I

PPV, T & I

PPV, CE

PPV, PPL

Enucleated

S. aureus

Cryo

NLP Hemophilus influenzae

Streptococcus pneumoniae

S. epidermidis

PPV

PPV/RD repair

PPV

20/40–2 (amblyopia)

Ivit, SC, Top

9

PPV, CE

S. aureus

IV, Ivit, SC

3

Enucleated (8 years) Enucleated 20/20

IV

7

LP (6 m)

20/200 (amblyopia)

20/60 (amblyopia)

Enucleated

Outcome

S. epidermidis

IV, Top

10 Enucleation

S. epidermidis

PPV, T & I

IV, Ivit, SC

S. aureus

Staphylococcus aureus

4

8

1

Enucleation Abscess drainage, sutures removal

Organism

Staphylococcus

IV, Top

IV

PO, Top

Procedures

30

14

5

Route of Time to diagnosis antibiotic administration (days)

3

1

3

7

2-3

3?

7

3

7

10

3

13

“few days”

5

Onset of symptoms (days)

Postoperative Infection

10.0

10.0

4.5

78.0

2.0

11.0

25.0

11.0

11.0

3.0 24.0

1966

Bedrossian [33]

Year Age published

Havener and Kimball [39] 1960

First author

Table 22.1. Endophthalmitis: onset of signs and symptoms, treatment, organism, and outcomes. (Blank No information, CE cataract extraction, Cryo cryotherapy, IV Intravenous, Ivit intravitreous, LP light perception, NLP no light perception, PO oral, PPL pars plana lensectomy, PPV pars plana vitrectomy, RD retinal detachment, SC subconjunctival, T & I tap and inject vitreous, Top topical). (Prepared by Aaron Miller, MD)

226 Chapter 22

 

(2) chloramphenicol ointment twice a day, or (3) no treatment. The no treatment arm was discontinued early when three of the initial eight patients randomized to the nontreatment arm developed a “severe mucopurulent conjunctivitis and had to return to the hospital” for treatment. This occurred on the third postoperative day in each case and none of the patients developed endophthalmitis. Prompt improvement was noted upon initiation of topical antibiotic therapy in all three patients. Of 51 patients in the fucithalmic group, 1 (2%) returned 3 days after surgery because of marked conjunctivitis and grew Hemophilus influenza from the conjunctiva. Of 45 patients in the chloramphenicol group, 3 (7%) returned on the second or third postoperative day because of a “frank mucopurulent conjunctivitis,” while 1 patient still had discharge at 9 days that cleared after a change of the patient’s antibiotic regimen. These authors concluded that antibiotics should be used routinely in children following strabismus surgery. The frequency of significant mucopurulent discharge reported in this study in both the treated and placebo groups seems extraordinarily high in our experience, making application of the results of this study to routine practice difficult. These findings are in contrast to the findings reported by other authors. Hagan and Dinning [21] randomized children to day surgery without medications or an overnight stay in the hospital with the use of postoperative oxyphenbutazone/chlor­ amphenicol ointment twice a day for 14 days. They found no difference in the level of inflammation or discomfort in either group. Wortham and co-workers [22] randomized each eye of 50 patients undergoing bilateral strabismus surgery to receive either a topical preparation of sulfacetamide-prednisolone solution or artificial tears. The patients were followed for 6 weeks after surgery for evidence of infection. No difference was found in the amount of lid swelling, corneal clarity, conjunctival injection, chemosis, or discharge among the treatment groups. These authors concluded that routine use of postoperative antibiotic drops as an adjunct to perioperative sterile preparation and prudent use of an antibiotic immediately at the culmination of surgery appeared to serve no benefit in otherwise uncomplicated strabismus surgery. Probably more important is for the strabismus surgeon to be aware of the potential signs and symptoms of endophthalmitis and review these signs and symptoms with patients and families after surgery and ensure that patients have ready access to the surgeon or his/her covering physician in the days and weeks immediately following surgery in the event that a problem develops. In many if not most cases of endophthalmitis, there is a delay of several days from onset of signs and symptoms to diagnosis of endophthalmitis (>Table 22.1). Among the 18 reported cases of endophthalmitis summarized in Table 22.1 with both time of onset of symptoms and diagnosis reported, the range between onset of symptoms and diagnosis was zero to 9 days, with only four patients diagnosed on the day of onset of symptoms. Systemic signs and symptoms related to strabismus surgery are so uncommon and unexpected that children who experience systemic signs and symptoms of illness are often first seen by their pediatrician for evaluation of what is believed to be a viral syndrome. If the pediatrician does not recognize the presence of a serious intraocular

22.3  Periocular Infection

infection, treatment as a typical viral syndrome may be recommended. Only when signs and symptoms progress, or the child returns for his/her regularly scheduled postoperative office visit with the ophthalmologists will the correct diagnosis of endophthalmitis be made. Thus a discussion with patients and parents about the signs and symptoms of a serious infection and instructions on what to do if concern arises is important after surgery. Our experience with endophthalmitis following strabismus surgery in adults also suggests that intraocular infection following strabismus surgery may sometimes produce different signs and symptoms during the early course of the infection. Two adults who developed endophthalmitis initially complained of floaters and not pain. The vitreous showed clear evidence of infection but the anterior chambers was clear. The numerous signs and symptoms that have been reported are summarized in Table 22.2.

22.3 Periocular Infection (Orbital and Preseptal Cellulitis) Orbital and preseptal cellulitis has been reported infrequently following strabismus surgery. Orbital cellulitis can be fulminant, presenting with the extreme proptosis, chemosis, eyelid swelling, and pain [23]. Prior to the discovery of antibiotics, the mortality rate from orbital cellulitis ranged from 20% to 50% and blindness occurred in 20% to 55% of survivors. The condition is rare enough following strabismus surgery that it may not be initially suspected and treatment may be delayed. Only a few cases reports about orbital cellulitis have populated the literature in the last few decades [24–27]. von Noorden has stated that the condition is either rare or that surgeons choose not to report it [25]. The validity of von Noorden’s statement may be underscored by the findings of the Periocular Infection Study Group [28], which surveyed members of the American Association for Pediatric Ophthalmology and Strabismus and identified 25 cases of cellulitis. Staphylococcus aureus was the cultured organism in the majority of cases. It has been suggested that cellulitis occurs following strabismus surgery in approximately 1 in 1100 cases [29]. Risk factors for development of cellulitis were not identified, but the authors raised the possibility that at least some of the infections might have been incidental. For example, one surgeon in the study group reported two patients who developed cellulitis after their strabismus surgery was cancelled because of the presence of an upper respiratory tract infection. Had surgery been performed, these infections would almost certainly have been characterized as a surgical complication. Another patient developed cellulitis in the unoperated eye associated with otitis media and bronchitis that was not recognized until after surgery. Presenting signs and symptoms of cellulitis varied in this study, though marked swelling was noted in 24 (96%) of 25 patients and severe pain was reported by 17 (68%) of 25 patients. Other signs and symptoms that were reported are listed in Table 22.3. The patient and/or family typically became

227

228

Postoperative Infection

Chapter 22

Table 22.2. Signs and symptoms of endophthalmitis and history of scleral perforation. (Prepared by Aaron Miller, MD) (+ Present, – specifically not present, ++ initial complaint, +! key diagnostic finding, blank no information) Author

Year published

Scleral Pain Decreased perforation vision

Havener and Kimball [39]

1960

+

Bedrossian [33]

1966

Gottlieb and Castro [40]

1970

McNeer [41]

1975

Weinstein et al. [42]

1979

Salamon et al. [12]

1982

Salamon et al. [12]

1982

Apple et al. [43]

1985

Uniat et al. [17] Kushner and Meyers [16] Bialasiewicz et al. [44]

1990

Thomas et al. [45]

1993

-

Kivlin and Wilson [28]

1995

-

Recchia et al. [13]

2000

-

+

Recchia et al. [13]

2000

-

+

Recchia et al. [13]

2000

-

Recchia et al. [13]

2000

-

Recchia et al. [13]

2000

-

+

+

Recchia et al. [13]

2000

-

+

+

Thorne and Maguire [46]

2000

-

+

+

Walton and Cohen [18]

2004

+

++

++

Ruby et al. [47]

2005

+ -

+

+

+

+

-

+

+

1988

+

+

+

1989

-

++

+

+ +

++

Marked swelling

24

Severe pain

17

Light sensitivity

8

Marked redness of the eye

3

Discharge

3

++ ++

++

Number of patients

Fever

++

++

Symptoms

Tearing Systemic

Photophobia Increased Proptosis Eyelid tearing swelling

+

Table 22.3. Ocular and systemic signs and symptoms of preseptal cellulitis after strabismus surgery [28] (Reproduced with permission from Kivlin JD and coworkers. Periocular infection after strabismus surgery. Journal of Pediatric Ophthalmology and Strabismus. Copyright © 1995, Slack, Inc.)

Ocular

Floaters

+

++

aware of unusual symptoms between 1 and 5 days following surgery. Fifty-six percent of the patients had experienced a routine postoperative course prior to the diagnosis of cellulitis. It has been our experience that the parent or patient who calls after surgery with a complaint of isolated lid swelling following strabismus surgery usually does not have cellulitis. On the other hand, the parent or patient who calls complaining of eyelid swelling and significant erythema almost always has cellulitis (>Fig. 22.2). Patients calling with concerns about lid swelling are therefore asked specifically about eyelid erythema.

1 11

Irritability

8

Lethargy

8

Nausea/decreased appetite

6

Insomnia from pain

1

Fig. 22.2. Preseptal cellulitis presenting 3 days following uncomplicated strabismus surgery

 

Lethargy Redness Fever Chemosis Corneal haze/edema

Anterior uveitis

22.4  Scleritis

Hypopyon

Abscess Globe Vitreous Subretinal ulceration haze/vitritis exudate

+ +

+

+

+

+

229

Reduced red reflex

+ +

+ +

-

+

+

+

+

+

+

+

-

+

-

+ ++

++

+ ++

+

+

+

+

+

-

+

+!

+

+

+

+

+ + + +

+

+

+

+

+

+

+

+

+

+

+

+

-

++

+ +

+! +

+!

+

+!

+

+

+! +! +

+

+!

+

+! +

+

+

+

+

+

+

+

Possible predisposing factors that have been suggested include excessive eye rubbing, unsuspected sinusitis, unreliable family, and poor hygiene [28]. Two cases reported by the Periocular Infection Study Group [28] were initially managed by a primary care physician who did not appreciate the potential seriousness of the condition following ophthalmologic surgery. Thus, patients and parents should be advised to consult their ophthalmologist immediately if there is a concern about postoperative infection. All cases of cellulitis in the Periocular Infection Study Group [28] report responded to antibiotic therapy, though only five were successfully treated with oral antibiotics alone, suggesting that hospitalization with intravenous antibiotics may be the preferred initial treatment option. This is in contrast to our experience with patients who present with postoperative preseptal cellulitis, who have generally responded favorably to oral antibiotics alone and hospitalization has rarely been necessary. Good hygiene, hand washing, and avoidance of eye rubbing following surgery may have a beneficial prophylactic effect and should be encouraged. It is unclear if the presence of a concurrent minor infection adversely affects the rate of developing cellulitis. This is compounded by the fact that it is often difficult to diagnose an upper respiratory tract infection and/or

+

+

+

+

+

+

sinusitis preoperatively. Kivlin and co-workers [28] suggested that if an upper respiratory tract infection or infection elsewhere develops after strabismus surgery it is reasonable to consider prescribing oral antibiotics on the assumption that the infection could be bacterial, rather than to assume it is of viral origin, thus reducing the risk of developing an ocular or periocular infection.

22.4 Scleritis Scleritis has been rarely reported following strabismus surgery. Because of its infrequency, it may be initially misdiagnosed and mismanaged. Hemady et al. [30] reported a case of scleritis in a 70-year-old man who began to complain of discomfort and ocular redness of his left eye following an inferior rectus muscle recession done to treat thyroid-related ophthalmopathy. His history was also notable for diabetes, hypertension, and atherosclerotic heart disease. He was initially treated for conjunctivitis and, when he failed to respond to treatment, he was referred for further evaluation 2 weeks later. B-scan ultrasonography revealed choroidal and scleral thickening, confirming a suspected diagnosis of posterior scleritis. Scleral

230

Postoperative Infection

biopsy revealed neutrophil invasion of vessel walls and mononuclear perivasculitis. Proteus mirabilis was cultured from the sclera and the infection responded immediately to intravenous antibiotic administration. Sykes et al. [31] reported an 86-yearold women with scleritis due to Hemophilus influenza who had undergone strabismus surgery 10 years earlier.

22.5 Subconjunctival Abscess Paakkala [32] reported 11 patients who developed a postoperative subconjunctival abscess at the operative site among 1467 muscles operated for strabismus. The problem was diagnosed an average of 7 days after surgery. Purulent material was noted near the suture while it was being removed in each case. Chromic gut suture had been used in six of the cases, plain gut suture in four cases, and Dacron suture in two cases. The presence of a subconjunctival abscess in association with endophthalmitis (and possibly casually related) has been reported [14]. Large subconjunctival abscesses can develop (>Fig. 22.3). A subconjunctival abscess diagnosed following strabismus surgery should be surgically drained as soon as practical after it is recognized. Drainage can be done in the office or in the operating room, depending upon the severity and location of the abscess and cooperation of the patient. Oral antibiotics may be sufficient, but intravenous antibiotics may be considered in severe cases. Affected patients should undergo a dilated fundus examination and slit lamp examination to assess for intraocular infection and should be followed closely for development of endophthalmitis and/or orbital cellulitis. Affected patients should be advised of warning signs of these serious potential complications.

Fig. 22.3. Large subconjunctival abscess several days following strabismus surgery. (Courtesy of Richard A. Saunders, MD)

Chapter 22

22.6 Corneal Ulcer Bedrossian [33] reported a 24-year-old healthy nurse who developed a corneal abscess due to Staphylococcus aureus 5 days following strabismus surgery. The patient developed a hypopyon 2 days later. She was treated with topical and oral antibiotics and had a favorable outcome. We are aware of one case of bilateral Pseudomonas corneal ulceration following corneal bridle suture placement to facilitate strabismus surgery. There are several reports of patients who developed neurotropic corneal ulceration following strabismus surgery, most with special susceptibility to the condition. Zehl and Snell [34] reported a 9-year-old boy with a fifth and seventh nerve palsy who underwent horizontal strabismus surgery. The child developed multifocal neurotropic corneal ulceration. He was treated with a contact lens and lubricating ointments and ultimately healed. These authors felt that operating on such an eye was associated with an increased risk of corneal ulceration, but they did not feel that the risk was unacceptable. Wintle et al. [35] reported a patient with Pendred syndrome who had a bilateral abducens nerve palsy. Two months following bilateral transposition surgery, the child developed corneal ulceration involving the inferior aspect of the left cornea. Marked reduction in corneal sensitivity was ultimately noted and the author suggested that corneal sensitivity should be evaluated prior to surgery in suspicious situations.

22.7 Concurrent Systemic Infections The decision on whether to perform or postpone strabismus surgery on a patient with a concurrent systemic infection can be difficult. Certainly, a febrile patient or a patient with a known serious systemic infection should not undergo strabismus surgery. On the other hand, the presence of recently treated otitis media, mild ongoing sinusitis, and/or mild upper respiratory tract infection is quite common in the pediatric population, especially during the winter months. The infrequency of periocular and intraocular infection following strabismus surgery renders it difficult, if not impossible, to draw a clear association between the presence of such concurrent “minor” infections and the development of periocular and intraocular infection. The decision to operate should be made on a case-by-case basis after a discussion of the pros and cons of delaying surgery with the patient and/or parent. In contrast, the presence of a periocular infection, such as severe blepharitis or a nasolacrimal duct obstruction, warrants serious consideration for postponing strabismus surgery until the condition has been resolved. Any condition that directly increases the level of bacterial exposure at the operative site has the potential to increase the risk of postoperative infection and thus strabismus surgery should be avoided in their presence. In a child with concurrent strabismus and nasolacrimal duct obstruction it is our practice to treat the nasolacrimal duct obstruction with a probing procedure and defer strabismus surgery until the lacrimal drainage system is functional, unless

 

such an obstruction is unilateral and the strabismus surgery can be performed on the nonobstructed eye.

22.8 Subacute Bacterial Endocarditis Prophylaxis Prophylactic antibiotic administration for patients who are susceptible to bacterial endocarditis is recommended for certain surgical procedures, such as surgery involving the respiratory tract, gastrointestinal tract, and the genitourinary tract. Prophylactic antibiotic administration is not required for strabismus surgery because of a low risk of bacteremia associated with strabismus surgery.

22.9 Concurrent Surgeries Pediatricians and parents often wish to combine surgical procedures during a single operative setting to eliminate the need for a second trip to the operating room. The most common request we receive is to coordinate placement of myringotomy tubes and/or tonsillectomy and adenoidectomy. Is it safe to perform strabismus surgery in close association with one of these procedures? An answer to this question is not available through evidence-based medicine, and the decision should be made on a case-by-case basis. We base this decision on several factors including the general health of the child, the risk posed to the child by a second exposure to anesthesia, and the nature of the concurrent procedure that is proposed. Not infrequently, the strabismus surgeon is asked to perform strabismus surgery on a child who is undergoing an adenoidectomy. Bacteremia has been reported in 14% of healthy children undergoing adenoidectomy [36] and up to 40% of healthy children undergoing tonsillectomy and adenoidectomy [37], although others have reported that the condition is rare [38]. Because the source of infection causing endophthalmitis following strabismus surgery is not known and because use of prophylactic antibiotics does not prevent bacteremia after adenoidectomy, some strabismus surgeons may feel uncomfortable recommending strabismus surgery in this setting and will recommend performing strabismus surgery on a separate day. Recognizing that the risk of endophthalmitis is very rare after strabismus surgery and that there is no hard evidence to support either position, it would be hard to disagree with either approach.

22.10  Special Situations

ration mandates a frank discussion with the patient about the associated risks and their potential consequences. Additional steps to reduce the risk of endophthalmitis may be considered such as utilizing techniques for strabismus surgery that do not require placement of sutures in the sclera (Chap. 21).

References 1. 2. 3.

4.

5.

6.

7. 8.

9.

10. 11.

12. 13.

14. 15.

22.10 Special Situations Monocular patients are at particular risk for life-altering consequences from vision loss in their sound eye. Strabismus surgery can be performed on a patient with severe unilateral visual impairment and sometimes is required on the sound eye in order to maximally correct the patient’s problem. Surgical prepa-

16.

17.

Schiff FS (1990) The shouting surgeon as a possible source of endophthalmitis. Ophthalmic Surg 21:438–440 Apt L, Miller KM (1992) Occult glove perforation during ophthalmic surgery. Trans Am Ophthalmol Soc 90:71–95 Wright JG, McGeer AJ, Chyatte D, Ransohoff DF (1991) Mechanisms of glove tears and sharp injuries among surgical personnel. J Am Med Assoc 266:1668–1671 Nakazawa M, Sato K, Mizuno K (1984) Incidence of perforations in rubber gloves during ophthalmic surgery. Ophthalmic Surg 15:236–240 Centers for Disease Control and Prevention (CDC) (1996) Outbreaks of postoperative bacterial endophthalmitis caused by intrinsically contaminated ophthalmic solutions – Thailand, 1992, and Canada, 1993. MMWR Morb Mortal Wkly Rep 45:491–494 Doyle A, Beigi B, Early A, Blake A, Eustace P, Hone R (1995) Adherence of bacteria to intraocular lenses: a prospective study. Br J Ophthalmol 79:347–349 Olitsky SE, Vilardo M, Awner S, Reynolds JD (1998) Needle sterility during strabismus surgery. J AAPOS 2:151–152 Carothers TS, Coats DK, McCreery KM et al (2003) Quantification of incidental needle and suture contamination during strabismus surgery. Binocul Vis Strabismus Q 18:75–79 Wang N, Coats DK, Paysse EA, Saunders RA, Wilson P, Rossman SN (2000) The significance of cryotherapy in reducing bacterial count during experimental scleral perforation. In: de Faber JT (ed) European Strabismological Association. Swets and Zeitlinger, Barcelona, pp 177–180 Knobloch R, Lorenz A (1962) [On serious complications after strabismus operations.] Klin Monatsbl Augenheilkd 141:348–353 Simon JW, Lininger LL, Scheraga JL (1992) Recognized scleral perforation during eye muscle surgery: incidence and sequelae. J Pediatr Ophthalmol Strabismus 29:273–275 Salamon SM, Friberg TR, Luxenberg MN (1982) Endophthalmitis after strabismus surgery. Am J Ophthalmol 93:39–41 Recchia FM, Baumal CR, Sivalingam A, Kleiner R, Duker JS, Vrabec TR (2000) Endophthalmitis after pediatric strabismus surgery. Arch Ophthalmol 118:939–944 Rosenbaum AL (2000) Endophthalmitis after strabismus surgery. Arch Ophthalmol 118:982–983 Good WV, Hing S, Irvine AR, Hoyt CS, Taylor DS (1990) Postoperative endophthalmitis in children following cataract surgery. J Pediatr Ophthalmol Strabismus 27:283–285 Kushner BJ, Meyers FL (1989) Good visual outcome after endophthalmitis in an eye previously treated successfully for amblyopia. J Pediatr Ophthalmol Strabismus 26:69–71 Uniat LM, Olk RJ, Kenneally CZ, Windsor CE (1988) Endophthalmitis after strabismus surgery with a good visual result. Ophthalmic Surg 19:42–43

231

232

Postoperative Infection 18. Walton RC, Cohen AS (2004) Staphylococcus epidermidis endoph­ thalmitis following strabismus surgery. J AAPOS 8:592–593 19. Results of the Endophthalmitis Vitrectomy Study (1995) A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of postoperative bacterial endophthalmitis. Endophthalmitis Vitrectomy Study Group. Arch Ophthalmol 113:1479–1496 20. Kearns PP, Cullen JF (1992) Fucithalmic, chloramphenicol or no treatment after squint surgery in children. A single blind randomised study. Acta Ophthalmol (Copenh) 70:132–134 21. Hagan MC, Dinning WJ (1987) Day case strabismus surgery without post-operative ocular medication. A masked randomised study. Eye 1 (Pt 5):581–584 22. Wortham ET, Anandakrishnan I, Kraft SP, Smith D, Morin JD (1990) Are antibiotic-steroid drops necessary following strabismus surgery? A prospective, randomized, masked trial. J Pediatr Ophthalmol Strabismus 27:205–207 23. de Sa L, Hoyt CS, Good WV (1992) Complications of pediatric ophthalmic surgery. Int Ophthalmol Clin 32:31–39 24. Wilson ME, Paul TO (1987) Orbital cellulitis following strabismus surgery. Ophthalmic Surg 18:92–94 25. Von Noorden GK (1972) Orbital cellulitis following extraocular muscle surgery. Am J Ophthalmol 74:627–629 26. Weakley DR (1991) Orbital cellulitis complicating strabismus surgery: a case report and review of the literature. Ann Ophthalmol 23:454–457 27. Palamar M, Uretmen O, Kose S (2005) Orbital cellulitis after strabismus surgery. J AAPOS 9:602–603 28. Kivlin JD, Wilson ME Jr. (1995) Periocular infection after strabismus surgery. The Periocular Infection Study Group. J Pediatr Ophthalmol Strabismus 32:42–49 29. Locatcher-Khorazo D, Seegal BC, Gutierrez EH (1972) Postoperative infections of the eye. In: Locatcher-Khorazo D, Seegal BC (eds) Microbiology of the eye. CV Mosby, St Louis, Mo., pp 80–82 30. Hemady R, Sainz de la Maza M, Raizman MB, Foster CS (1992) Six cases of scleritis associated with systemic infection. Am J Ophthalmol 114:55–62 31. Sykes SO, Riemann C, Santos CI et al (1999) Haemophilus influ­ enzae associated scleritis. Br J Ophthalmol 83:410–413 32. Paakkala AM (1982) Surgical treatment of strabismus. A retrospective investigation of results of surgical treatment of horizontal strabismus. Acta Ophthalmol Suppl 156:1–107

Chapter 22 33. Bedrossian EH (1966) Hypopyon keratitis: following muscle surgery. Am J Ophthalmol 61:1530–1532 34. Zehl DN, Snell AC (1977) Extraocular muscle surgery in the presence of complete paralysis of the fifth, sixth and seventh cranial nerves. J Pediatr Ophthalmol 14:76–78 35. Wintle RV, Choong YF, Laws DE (2003) Unilateral corneal anaesthesia and ulceration following squint surgery in a child with Pendred syndrome and bilateral sixth nerve palsy. Br J Ophthalmol 87:1192 36. Sanchez-Carrion S, Prim MP, De Diego JI, Sastre N, Pena-Garcia P (2005) Bacteremia following pediatric adenoidectomy. Int J Pediatr Otorhinolaryngol 69:1547–1550 37. Van Eyck M (1976) Bacteremia after tonsillectomy and adenectomy. Acta Otolaryngol 81:242–243 38. Okur E, Aral M, Yildirim I, Kilie MA, Ciragil P (2002) Bacteremia during adenoidectomy. Int J Pediatr Otorhinolaryngol 66:149–153 39. Havener WH, Kimball OP (1960) Scleral perforation during strabismus surgery. Am J Ophthalmol 50:807–808 40. Gottlieb F, Castro JL (1970) Perforation of the globe during strabismus surgery. Arch Ophthalmol 84:151–157 41. McNeer K (1975) Three complications of strabismus surgery. Ann Ophthalmol 7:441–446 42. Weinstein GS, Mondino BJ, Weinberg RJ, Biglan AW (1979) Endophthalmitis in a pediatric population. Ann Ophthalmol 11:935–943 43. Apple DJ, Jones GR, Reidy JJ, Loftfield K (1985) Ocular perforation and phthisis bulbi secondary to strabismus surgery. J Pediatr Ophthalmol Strabismus 22:184–187 44. Bialasiewicz AA, Ruprecht KW, Naumann GO (1990) [Staphylococcal endophthalmitis following squint surgery.] Klin Monatsbl Augenheilkd 196:86–88 45. Thomas JW, Hamill MB, Lambert HM (1993) Streptococcus pneumoniae endophthalmitis following strabismus surgery. Arch Ophthalmol 111:1170–1171 46. Thorne JE, Maguire AM (2000) Hemophilus aegyptius endophthalmitis following strabismus surgery. J Pediatr Ophthalmol Strabismus 37:52–53 47. Ruby A, Shaikh S, Khammar AJ, Trese M (2005) Suprachoroidal septic effusion leading to panophthalmitis following strabismus surgery. J Pediatr Ophthalmol Strabismus 42:250–252

Chapter

Slipped and Lost Muscles

23

23 Other than an intraocular infection or a retinal detachment with loss of vision, a lost muscle is one of the most devastating complications that a strabismus surgeon can face in the intraoperative or postoperative period. This chapter will discuss the various causes of slipped and lost muscles along with the stretched scar syndrome. It is useful to consider slipped muscles, lost muscles and muscle with stretched scars as occurring in three distinct categories (>Table 23.1). These categories are helpful for the purpose of the discussion of etiology, diagnosis, evaluation and treatment, as well as prevention. Differences in the approach to diagnosing and treating slipped muscle versus lost muscle will be reviewed. In addition, while a muscle that has developed a stretched scar at its new insertion is technically not a slipped or lost muscle, this condition is said to often be confused with a slipped muscle and its diagnosis and management will also be reviewed in this chapter. A slipped muscle is a disinserted rectus muscle, which, after reattachment to the globe, retracts posteriorly within its muscle capsule, while the empty capsule remains attached to the sclera at the intended new insertion site. A slipped muscle should be differentiated from a lost muscle in which no portion of the muscle, including its capsule, remains attached to the sclera. There are four causes of lost muscles, three of which occur as a result of surgery, including inadvertent severing of a muscle from the globe, a surgically snapped or torn muscle, and late detachment of the muscle from the globe. The fourth type is a nonsurgical traumatic muscle detachment from the globe.

23.1 The Slipped Muscle The term slipped muscle generally refers to a disinserted rectus muscle, which, after reattachment to the globe, retracts posteriorly within its muscle capsule, while the empty muscle capsule remains attached to the sclera [1–3]. A slipped muscle should be differentiated from a lost muscle in which no portion of the muscle remains attached to the sclera (>Fig. 23.1). The incidence of slipped muscles is unknown. Several series in the literature discuss both slipped and lost muscles as a single entity. It is beneficial, however, to consider these conditions as two separate entities because their cause, treatment and prevention may vary significantly. Plager and Parks [3] reported 52 patients with 62 slipped rectus muscles. Murray [4] reported 16 cases of slipped muscles and Knapp [5] described more than 60 cases of slipped and/or lost muscles.

23.1.1 Presentation and Diagnosis A common theme is present in most reports on slipped muscles. Typically, the patient presents shortly after strabismus surgery with a moderate to large consecutive deviation and

Table 23.1. Classification of slipped and lost muscles I.

Slipped muscle

II.

Lost muscle

A. i.

Inadvertent disinsertion

ii.

Snapped or torn

B. C. III.

Intraoperative loss

Late loss Loss secondary to trauma Stretched scar syndrome

Fig. 23.1. Slipped muscle. Note thin pseudotendon (muscle capsule) on hook

234

Slipped and Lost Muscles

a small to medium duction deficit (>Fig. 23.2). The duction deficit is often subtle. In most series, the medial rectus muscle was the most commonly involved muscle and in some series it represented the only muscle involved [4, 6]. It is unclear if this is because the problem is more prone to occur with a medial rectus muscle, or if the medial rectus muscle is operated on more frequently than other extraocular muscles, and thus may be over represented. Often, the initial diagnosis of a slipped muscle is not made by the referring ophthalmologist. Instead, the patient is referred after a second strabismus surgery has been performed to correct the consecutive deviation and fails to achieve satisfactory alignment. Usually, the distinction between a slipped versus a lost muscle can be made during standard clinical examination. Although the patient may have a large consecutive deviation, the duction deficit is usually less than would be expected if the muscle was completely detached from the globe. A neuroimaging study, such as computed tomography (CT) scanning or magnetic resonance imaging (MRI), can be helpful in

Chapter 23

confirming the diagnosis of a slipped muscle (or ruling out a lost muscle) by demonstrating that the muscle tendon itself is not attached to the globe but rather is in near proximity to the globe [6, 7] (>Fig. 23.3). At the time of surgical exploration, the surgeon should anticipate finding the muscle capsule at­ tached to the globe at or near the intended location for muscle placement during the previous surgery. Once the muscle capsule is identified, it is carefully followed posteriorly where the muscle/tendon itself will be found attached to muscle capsule (>Fig. 23.4). The entire muscle insertion may slip in the cap­ sule evenly, or one pole of the insertion may slip asymmetrically compared to the other. A slipped rectus muscle is often suspected because of the presence of a consecutive deviation, a duction limitation, and a negative spring-back test (>Table 23.2). A spring-back test is performed intraoperatively prior to making a conjunctival incision. The test depends on intact elastic forces of the rectus muscles to briskly restore the eye near to the primary position following a large passive duction in the direction opposite the

Fig. 23.2. Mild adduction deficit in both eyes following medial rectus muscle recession due to a slipped medial rectus muscle in both eyes. Intraoperative findings shown in Fig. 23.1

Fig. 23.3. CT scan with bottom arrow showing slipped left medial rectus. The top arrow shows the muscle capsule still attached to the sclera. {Reprinted from Murray AD (1998) Slipped and lost muscles and other tales of the unexpected. Philip Knapp Lecture. J AAPOS 2:133–143, with permission from American Association for Pediatric Ophthalmology and Strabismus [4]}

Fig. 23.4. Slipped muscle after detachment of the pseudotendon from the globe. Note pseudotendon held in forceps with attachment of muscle to the capsule posteriorly

 

suspected slipped muscle (>Fig. 23.5). A muscle that has significantly slipped will often, but not always, fail to briskly return toward the primary position, and instead will remain near the position of maximum passive duction (>Fig. 23.6). In addition to simple visual inspection of the muscle, two simple tests, the see-through test (as taught by Jampolsky) and the step test [8], can help to confirm the diagnosis of a slipped muscle (>Table 23.2). Both tests are performed after surgical exposure and isolation of the muscle on a muscle hook. The see-through test is generally performed first. A muscle hook is generally not readily visible behind an intact rectus muscle or tendon (>Fig. 23.7). A muscle hook is generally readily visible behind the pseudotendon (muscle capsule) of a slipped muscle (>Fig. 23.1). The step test is performed by placing mild traction with a muscle hook on the global surface of the muscle and then sliding the muscle hook posteriorly. A step can usu-

23.1  The Slipped Muscle

ally be palpated during this maneuver at the junction between the pseudotendon and the rectus muscle or tendon if the muscle has slipped (>Fig. 23.8). This is in contrast to the smooth transition that occurs between the junction of a normal rectus muscle and its tendon. Table 23.2. Signs of a slipped rectus muscle Consecutive deviation Duction limitation Positive spring-back test Positive see through test Positive step test

Fig. 23.5a,b. Normal spring-back test. Note that the eye recoils immediately to the primary position after it is released (b)

Fig. 23.6. Abnormal spring-back test. With a lost or severely slipped muscle the eye fails to recoil back to the primary position after being displaced. In this case, the medial rectus muscle has been surgically detached from the globe

Fig. 23.7. The see-through test for a slipped muscle. A muscle hook is generally not readily visible behind a rectus muscle tendon, compared with visibility behind the pseudotendon of a slipped muscle as in Fig. 23.1

235

236

Slipped and Lost Muscles

Fig. 23.8a,b. The step test for a slipped muscle. Mild traction is placed on the global surface of the muscle as the hook is moved posteriorly. a A step can usually be palpated at the junction between the pseu-

Chapter 23

dotendon and the rectus muscle/tendon if the muscle has slipped, b compared to the smooth transition at the junction between a normal rectus muscle and its tendon

Fig. 23.9a,b. Repair of a slipped muscle. a Sutures are placed in the muscle/tendon posterior to the muscle capsule, and b the muscle is reattached to the sclera after detachment of the muscle capsule from the globe

 

23.1.2 Treatment Once the muscle/tendon has clearly been identified as attached to the muscle capsule, it should be isolated, secured with sutures (>Fig. 23.9a), and brought back in contact with the globe (>Fig. 23.9b). If a significant amount of time has elapsed since the original surgery, the muscle will generally be very contracted. Advancing a significantly contracted muscle to its previously intended new insertion on the sclera may lead to a significant overcorrection, necessitating modification of the original surgical plan. In general, during the repair of a long-standing slipped muscle, we place mild anterior traction on the muscle while holding the eye in the primary position (>Fig. 23.10a). The muscle is reattached to the globe with temporary sutures at the position where it makes contact with the globe in the primary position (>Fig. 23.10b). Forced traction testing is then done. We prefer to find the point at which we begin to note resistance to forced traction testing at approximately three-quarters full duction in the direction of the slipped muscle’s antagonist. The muscle position is adjusted and the sutures finally converted to a permanent knot once this is achieved (>Fig. 23.10c). We do not usually place slipped muscles on adjustable sutures, but rather place the antagonist on an adjustable suture if this is

Fig. 23.10a–c. Determining where to reattach a long-standing slipped muscle. a Mild anterior traction is placed on the muscle after it has been secured with suture and the muscle capsule detached from the globe. b The muscle is reattached to the globe with temporary sutures at the position where it makes contact with the globe. The muscle position is adjusted until mild resistance to forced traction testing is noted starting at about three-quarters full duction into the field of action of the antagonist. c The sutures are then converted to a permanent knot

23.1  The Slipped Muscle

deemed necessary. The vast majority of the time we do not use adjustable sutures in the repair of a slipped muscle. Because accurate alignment may be impossible in this setting due to difficulties in deciding where to attach the muscle, patients and parents should be advised that further surgery may be needed after the muscle has been reattached and ocular rotations improved. Once recognized, abnormal ocular alignment due to a slipped muscle can virtually always be corrected with surgery. The success rate is high in most series.

23.1.3 Prevention In theory, a slipped muscle should be a preventable event. Full thickness locking bites which incorporate the muscle, and not just the muscle capsule, should prevent the muscle from slipping within its muscle capsule (>Fig. 23.11). If the muscle capsule is thick, making clear identification of the muscle difficult, the anterior portion of the muscle tendon should be cleaned of fascial attachments to allow more precise placement of sutures in the muscle tendon. Surgeons who do not regularly perform strabismus surgery are typically most concerned about making the scleral needle passes deep enough to prevent complete detachment of the muscle. While this is obviously also critical to

237

238

Slipped and Lost Muscles

Chapter 23

Fig. 23.11a,b. Etiology of a slipped muscle. a Suture is inadvertently placed in the muscle capsule, rather than the muscle. b Traction on the suture readily demonstrates that the suture is not located in the muscle as the muscle capsule stretches anteriorly

Fig. 23.12. Producing a true locking bite on the muscle border

the success of the surgery, the importance of the full thickness locking bites to secure both the muscle and the muscle capsule to the sclera at the time of muscle reattachment should not be overlooked. Mims [9] has described a technique to ensure that a true locking bite is achieved (>Fig. 23.12). Some surgeons make use of a double locking bite to provide additional security. We do not generally find it necessary to place a second locking bite if the first is made correctly, except when operating on severely restricted muscles, such as those commonly seen in patients with thyroid-related ophthalmopathy.

23.2 The Lost Rectus Muscle A lost extraocular muscle can occur following any ophthalmic surgical procedure. The complication most commonly occurs following strabismus surgery or retina surgery and generally involves rectus muscles. It can also occur as a result of trauma

or surgery on adjacent structures, such as endoscopic sinus surgery [10] (>Fig. 23.13). Unlike a slipped muscle, when an extraocular muscle is lost, no direct attachment remains between the muscle tendon and the globe. The muscle and its capsule both retract posteriorly into the orbit. The term “lost” muscle is technically incorrect since the location of the muscle is known to be in the posterior orbit. The term “detached” muscle is probably superior, but the term lost muscle is so widely used in the ophthalmologic literature that the term will be used in this discussion. A patient with a lost rectus muscle almost always presents within hours or days after surgery. At the time of presentation, a large consecutive strabismus is seen, typically with an associated large duction deficit. Though most patients present for evaluation within hours or days after surgery, late loss of a muscle has been reported up to 5 weeks after the surgery [5]. This scenario may be particularly likely following retinal surgery where an encircling element such as a silicone buckle gradually erodes through the rectus muscle insertion (>Fig. 23.14).

23.2.1 Clinical Presentation and Diagnosis The clinical presentation is usually helpful in differentiating between a slipped and a lost muscle. A patient with a slipped muscle may have straight appearing eyes in the immediate postoperative period until full muscle function returns and gradually pulls the muscle posteriorly into the muscle capsule. A patient with a lost muscle will generally, though not always, present with a large consecutive deviation in the immediate postoperative period. In addition, the duction deficit seen in a patient with a lost muscle is almost always very large, in contrast to the smaller duction deficit usually seen with a slipped muscle. As with a slipped muscle, the medical rectus muscle is the most commonly involved muscle to experience this complication. Plager and Parks [11] reported 25 cases of lost extraocular muscles: 21 occurred during strabismus surgery; of

 

23.2  The Lost Rectus Muscle

Fig. 23.14. Lost (detached) right inferior rectus muscle due to erosion by a scleral buckle that occurred several weeks after surgery. See Fig. 27.14 for slitlamp photo of the involved eye

23.2.1.1 Intraoperative Muscle Loss

Fig. 23.13a,b. Lost medial rectus muscle following endoscopic sinus surgery. a The patient developed an acute exotropia with inability to adduct the involved eye past midline. b CT scan of a second patient demonstrating disruption of the medial orbital wall and medial rectus muscle

those, 6 muscles were lost due to unintentional transection of an adjacent muscle at the time of surgery. Murray [4] reported 37 cases of lost extraocular muscles. In his series, 32 occurred as a result of trauma and only 2 occurred during strabismus surgery. The management of a lost extraocular muscle depends largely on the mechanism by which the muscle has been lost and the timing of recognition and intervention.

Inadvertent detachment of an extraocular muscle can occur with almost any ophthalmologic surgical procedure, including pterygium surgery (>Fig. 23.15). If an extraocular muscle is lost during an ophthalmic surgical procedure, it should be retrieved immediately, if possible. Generally, exposure of the surgical site is better at the time of the initial surgery and the newly exposed tissue planes may make identification and retrieval of a lost muscle easier than if surgical repair is attempted hours or days later. The surgeon should avoid purposeless exploration in search of a lost muscle, a practice that can significantly worsen the situation, resulting in hemorrhage, fat intrusion into the surgical site, and other complications. If the operating surgeon is not familiar with the techniques of exploration to locate a lost extraocular muscle, it is best to terminate the intended surgical procedure and refer the patient to a skilled strabismus surgeon as soon as possible. Though optimal to make the repair during the initial operation, later repair is far superior to the damage that may occur during aimless exploration. If the muscle is lost during a nonstrabismus procedure, the surgeon

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Chapter 23

Fig. 23.15. Lost medial rectus muscle following pterygium surgery

should consider consulting a strabismus surgeon to assist with retrieval and repair while the patient is in the operating room, if the lost muscle is not identified with minimal, careful exploration. While this represents the optimal scenario, it is rarely practical and the repair is often done later when the strabismus surgeon is available. The technique of retrieval and repair of a lost muscle is reviewed below. In most cases, intraoperative loss of an extraocular muscle can be avoided with proper surgical technique. Careful identification and isolation of rectus muscle in the vicinity of the surgical field during strabismus and nonstrabismus procedures is an important step in the prevention of accidental detachment or transaction of a muscle. An important preventive measure in reducing the risk of a lost muscle during rectus muscle recession surgery is to limit dissection of the posterior intermuscular septum, muscle capsule, and muscle pulley. Excessive dissection of these structures does not enhance the effect of recession surgery [12] but increases the chance that the muscle

will retract into the posterior orbit if control of the distal aspect of the muscle is lost. Sutures used during strabismus surgery should be handled carefully, preferably with smooth instruments, as instruments with teeth and rough edges can result in damage to the suture material, causing weakness of the suture, reducing its tensile strength with resulting reduction in the strength of the new muscle attachment to the sclera.

23.3 The Snapped or Torn Extraocular Muscle Snapping or tearing an extraocular muscle apart can occur during strabismus and during other ophthalmologic surgical procedures and can involve any of the extraocular muscles. The muscle will usually rupture at the muscle–tendon junction during manipulation that exceeds the breaking point of the muscle [13–15] (>Fig. 23.16). Most cases of intraoperative

Fig. 23.16. Typical location of intraoperative muscle rupture in the pulled in two syndrome (PITS)

 

Fig. 23.17a,b. Repair of a ruptured muscle. a, b End-to-end anastomosis if the distal aspect of the muscle is intact, or c suturing the proximal aspect of the muscle directly to the sclera and performing a double

muscle rupture reported in the literature have occurred in adult patients, many with serious underlying systemic illnesses. The muscle is often reported to pull apart with mild traction and has been referred to as the pulled in two syndrome (PITS) [13, 15]. This condition most commonly involves the medial and inferior rectus muscles. Because the muscle rupture typically occurs well posterior to the muscle insertion into the sclera, retrieval of the proximal, lost aspect of the muscle is rendered more difficult, and is often impractical. Exploration in an attempt to locate the proximal end of the muscle should be carried out in a manner similar to that described for retrieval of a muscle which has been lost intraoperatively, as described below. If the proximal end of the muscle can be retrieved, it may be possible to perform an endto-end anastomosis of the proximal and distal segments of the muscle, assuming that the distal muscle segment is still intact and attached to the globe (>Fig. 23.17). In most cases, this will provide acceptable alignment in primary position though the action of the damaged muscle will usually be significantly reduced [4]. If the distal aspect of the muscle is inadequate for an end-to-end anastomosis, the proximal muscle segment can usually be sutured directly to the sclera. A double marginal myotomy (Chap. 15) may be required to allow the muscle to be sutured anterior to the equator of the globe, a position usually required to minimize the risk of a primary position deviation and a severe duction limitation (>Fig. 23.17). Temporary mechanical fixation of the globe to reduce tension on this tenuous union may be helpful in some cases (Chap. 15) In some cases, it may be possible to retrieve the muscle from within the orbit through an orbitotomy at a late date. In most cases, the outcome is likely to be alignment in the primary position and limited function of the involved muscle. If the muscle cannot be retrieved, a transposition procedure is required [15] (Chap. 11).

23.4  Delayed Loss of an Extraocular Muscle

marginal myotomy, if needed to allow the muscle to be placed anterior to the equator

23.4 Delayed Loss of an Extraocular Muscle For purposes of this discussion, delayed loss of an extraocular muscle is considered to be one in which loss of the muscle is recognized at some point following the completion of a surgical procedure. This definition includes cases in which the muscle truly does lose its attachment to the globe after surgery and cases where the loss occurs at the time of surgery, but is not recognized until a later date. Affected patients generally present with a large consecutive strabismus and a pronounced duction deficit. The diagnosis is usually readily apparent. Imaging studies may be helpful in selected cases to confirm the diagnosis, but is not always required if the clinical diagnosis is clear. Magnetic resonance imaging is considered to be superior in most cases as it allows better visualization of the muscle [7] (>Fig. 23.18). In addition, dynamic magnetic resonance imaging allows visualization of the globe in different gaze positions in cooperative patients [16] which can be

Fig. 23.18.. Magnetic resonance imaging of the orbit demonstrating a lost medial rectus muscle.

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helpful in diagnosis and surgical planning. Magnetic resonance imaging may also help in the differentiation between a muscle which has been lost due to detachment from the globe versus a muscle that has been lacerated or ruptured. In the latter case, the proximal portion of the muscle may be visualized within the orbit while the distal portion of the muscle may be seen still attached to the sclera. Magnetic resonance imaging can help to rule out a muscle paralysis, a condition that can rarely be confused with a lost or lacerated muscle if it occurs shortly after an ophthalmologic surgical procedure. Generally, this is not a source of confusion but in cases where the preoperative history is questionable or unknown, it may be helpful. Exploration with definitive surgical repair should be undertaken as soon as practical. Earlier surgical exploration may allow identification of suture material that is still partially attached to the lost extraocular muscle, greatly simplifying repair. Timely repair also minimizes contracture of both the antagonist and the lost muscle, which, when present, increases the complexity of treatment. Treatment options are discussed in Sect. 23.6.

23.5 Traumatic Disinsertion of an Extraocular Muscle Both blunt and penetrating trauma can result in extraocular muscle detachment from the globe (>Fig. 23.19). In some reported series, trauma represents the overwhelming majority of cases of lost muscles. The patient generally presents with an acute onset, large angle strabismus and a large duction deficit. The differential diagnosis includes muscle paralysis and restrictive strabismus due to muscle entrapment in an orbital fracture. Initial evaluation should include careful assessment to rule out serious associated systemic and/or ocular injuries. Treatment of vision- and/or life-threatening injuries obviously takes precedence over repair of a traumatically detached

Fig. 23.19. Computed tomography scan demonstrating a traumatic rupture of the right medial rectus muscle

Chapter 23

extraocular muscle. Once these more serious problems have been managed and the patient is considered medically stable, detailed evaluation of the cause of the patient’s ocular motility disturbance is appropriate and may include forced duction testing, forced generation testing, and neuroimaging studies of the orbit. The timing of surgical exploration and repair depends on several variables. Early exploration and treatment should be considered to prevent contracture of both the detached muscle and the antagonist muscle. If there is significant concurrent hemorrhage and/or edema, a delay in surgical exploration may allow for better assessment of the motility disturbance, altering surgical planning. Furthermore, resolution of hemorrhage and/or edema usually makes surgical repair less complex because it allows better visualization of the affected muscle.

23.6 Surgical Treatment of the Lost Extraocular Muscle 23.6.1 Retrieval and Reattachment If the muscle capsule and intermuscular septum have undergone extensive dissection prior to the muscle being lost, the muscle will commonly retract through Tenon’s capsule to enter the posterior orbit. The surgeon should identify the potential space within Tenon’s capsule through which the muscle has retracted. Repair is optimally carried out through a large limbal incision, and the surgeon may wish to convert to a limbal incision if surgery was initiated through a fornix incision (Chap. 8). The basic steps required to locate a lost muscle in this situation involve retraction of the conjunctival flap and Tenon’s capsule anteriorly to expose the global surface of Tenon’s capsule. The global surface of Tenon’s capsule is visually inspected and delicately manipulated with fine toothed forceps in an attempt to locate the potential space representing the ruminants of the muscle capsule passing through Tenon’s capsule. A common mistake is to attempt to locate the lost muscle along the surface of the globe posteriorly. Rather, the surgeon should recognize that the paths of the extraocular muscles are guided and restrained by the rectus muscle pulley system and, instead of coursing along the globe, the rectus muscles course posteriorly and toward the adjacent orbital wall to enter the pulley mechanism. Exploration should proceed along the adjacent orbital wall, rather than adjacent to the globe (>Fig. 23.20). If the surgeon is unable to locate the lost muscle during the course of the exploration, a decision must be made whether to proceed with alternative treatment, such as a ­muscle transposition procedure, or to defer surgery to another day when further evaluation and other treatment modalities may be available to assist in the repair. Deferring definitive repair, such as a transposition procedure, when the muscle cannot be located may offer some significant benefits in many situations, and the surgeon must make this determination on a case-by-case basis. There are no rules on when to proceed with a transposition and when other

 

Fig. 23.20. Identification and retrieval of a lost muscle. a A lost rectus muscle will be found along the adjacent orbital wall. b A common mistake is to search for the muscle along the posterior aspect of the globe

treatment modalities should be considered. Assessment of postoperative motility may allow a more complete determination as to the best course of action for the specific patient and situation. Later retrieval of the lost muscle may be facilitated through the assistance of an oculoplastic surgeon skilled in surgery in the posterior orbit. Medial orbitotomy or trans-nasal endoscopic retrieval of a lost medial rectus muscle has been reported [17, 18].

23.6.2 Transposition Procedures when Attempted Retrieval and Reattachment is Unsuccessful If the detached or ruptured extraocular muscle cannot be retrieved and reattached to the globe without significant risk of complications, a backup surgical plan must be devised. Because partial disruption of the anterior ciliary circulation occurs as a result of loss of the anterior ciliary artery(ies) associated with the loss of the rectus muscle, the surgical plan must mitigate against the development of anterior segment ischemia, especially in susceptible patients (Chap. 20). A number of treatment options are available. The options in this setting include both transposition procedures and procedures to mechanically fixate the deviating eye in the primary position. The choices for transposition surgery include full tendon transposition,

23.7  Stretched Scar Syndrome

partial tendon transposition, and muscle union procedures using nonabsorbable suture or other appropriate material [15] (chap. 13). Botulinum may be injected into the antagonist to further enhance the procedure (Chap.16). While we once performed a full tendon transposition of the superior and inferior rectus muscles for the treatment of a lost medial rectus muscle in a young patient with a previous history of lateral rectus muscle surgery (thus disrupting the remaining anterior ciliary arteries), this should be done with extreme caution, and only in patients without systemic risk factors for anterior segment ischemia and after a long period of time has elapsed since the most recent strabismus surgery. Though timely repair is generally recommended, this is one situation where this rule does not apply. Repair with a transposition procedure usually involves techniques designed to spare some of the anterior ciliary circulation. Choices include a modified Hummelsheim-type procedure with or without injection of botulinum toxin into the antagonist muscle and a modified Jensen-type procedure, also known as a string Jensen procedure [15] (Chap. 27). We reported the successful use of a modified Hummelsheim-type procedure in the management a patient who suffered traumatic disruption of the medial rectus muscle during endoscopic sinus surgery [19]. For a lost inferior rectus muscle, anterior transposition of the inferior oblique muscle has been successful [20]. Regardless of the surgical plan devised, it is important for the strabismus surgeon to consider the risk of anterior segment ischemia and minimize this risk whenever possible. In addition, the patient should have realistic goals regarding their potential outcome. In most cases, alignment in primary position can be achieved, but with a significant duction limitation. A compensatory head posture or the use of postoperative prism may also be necessary as an adjunct to surgery in some cases and the possible need for adjunct procedures should be reviewed with the patient prior to repair.

23.7 Stretched Scar Syndrome Although it does not technically represent either a slipped or a lost extraocular muscle, patients who develop a stretched scar following strabismus surgery may have a similar presentation to patients who have a slipped muscle, but purportedly with some key differences. The stretched scar syndrome was first described by Ludwig [21], who examined a number of patients who had previously undergone recession of an extraocular muscle and presented with late-onset consecutive deviations, often many years following their initial procedure [22]. At the time of reoperation by Ludwig, patients were frequently found to have amorphous scar tissue separating the muscle tendon from the scleral attachment site (>Fig. 23.21). In several patients, initial repair of the overcorrection, which included removal of the scar, was followed by further recurrence. Ludwig postulated that scar lengthening after surgery was responsible for both the initial and secondary recurrent deviation. The rationale for this thought is substantial. Postoperative scar

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Fig. 23.21. Stretched scar. Note the presence of amorphous material between the muscle tendon and the sclera. {Reprinted from Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333, with permission from American Association for Pediatric Ophthalmology and Strabismus [22]}

Fig. 23.22. Stretching of surgical scars is known to occur following surgical wound repair. (Courtesy of Mary Brandt, MD)

lengthening is seen after other nonophthalmologic surgical procedures, including skin closure, hernia surgery, and tendon and ligament repairs (>Fig. 23.22). Ludwig estimated that up to 50% of late overcorrections could be due to this condition, which she coined the stretched scar syndrome. Ludwig and Chow [22] pointed out features which they believed helped to distinguish between a slipped muscle and a stretched scar. First, the overcorrection with a slipped muscle typically occurs shortly after surgery, generally within the first few weeks after surgery. In contrast, overcorrection in stretched scar syndrome usually occurs several months later. Second, a noticeable duction limitation is commonly associated with a slipped muscle, but is infrequently seen with a stretched scar.

Chapter 23

They found that when a duction limitation was present, it was usually minimal. In rare cases, ocular rotations may be significantly limited as a result of pronounced lengthening of the scar. Ludwig and Chow [22] described their experience in repairing 198 muscles during 134 operations in patients diagnosed with stretched scar syndrome. In this series, 73 procedures involved scar lengthening in 1 muscle and 59 procedures involved scar lengthening of 2 muscles [22]. In the majority of the ­2-muscle cases, the scar lengthening was symmetric. The average lengthening of the scar was approximately 4 mm regardless of the muscle involved. Of the patients who could clearly date the onset of their consecutive deviation, approximately half noted onset beginning within 4 months of the original surgery. The remainder noted the onset an average of 18 months (range 4 months to 43 years) after the initial procedure. Those who could not clearly date the onset typically described it as a slow and gradual process. Diagnosis of stretched scar syndrome can be suspected, but cannot be confirmed until the time of surgery to repair the deviation. During the surgical procedure, the distinction between the scar and the muscle tendon may be subtle. The scar can gradually blend into the tendon because the fibers of the scar often run parallel to the fibers of the tendon. An important surgical tip that can assist the surgeon in making a diagnosis of stretched scar syndrome is that the distinction between stretched scar and muscle tendon can often be made more easily by visualizing the global surface of the muscle after the muscle has been detached from the globe (>Fig. 23.23). This is presumably because anterior Tenon’s capsule becomes adherent to the orbital surface of the scar, obscuring the true nature of the tissue. The scar should be excised in its entirety after placing sutures in the muscle tissue posterior to the scar. Interestingly, once the scar tissue is removed, there tends to be a loss of the linear fiber arrangement and the scar takes on a more amorphous shape [22] (>Fig. 23.24) Histopathology of the excised stretched scar has demonstrated diffuse, dense connective tissue without the presence of skeletal muscle (>Fig. 23.25). The argument could be made that the patients seen by Ludwig actually had a slipped muscle. As evidence against this criticism, recurrence was more commonly seen in those patients who underwent surgical repair of stretched scar using absorbable sutures to reattach the muscle to the sclera. Of the procedures performed using absorbable sutures, 42% developed recurrent stretching versus 6% of those where nonabsorbable sutures were used, prompting Ludwig and Chow [22] to recommend nonabsorbable suture use to reattach the muscle. The long-term impact of the use of nonabsorbable sutures on the recurrence of a stretched scar is unknown. Use of nonabsorbable sutures has been shown to reduce the stretching of scars in skin, scalp, and fascia repair [23, 24]. Use of a central locking suture placed after scleral tunnels are made, in order to support the center of the tendon, has also been suggested [22]. Treatment of patients suspected of having recurrent strabismus from stretched scar syndrome begins with a decision regarding the need to address the scar itself. For patients who have had a stable consecutive deviation for an extended pe-

 

Fig. 23.23a,b. a Right lateral rectus muscle before disinsertion showing an indistinct scar-to-tendon junction (black arrow top). The insertion has been detached from the sclera and is suspended on 6-0 Polyglactin suture (white arrow bottom). Inspection of the inner surface of the lateral rectus demonstrates that the amorphous scar segment and transition to normal tendon (black arrow) become clear. White arrow indicates the scar insertion, suspended on a suture. {Reprinted from Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333, with permission from American Association for Pediatric Ophthalmology and Strabismus [22]}

23.7  Stretched Scar Syndrome

Fig. 23.24a,b. Appearance of a stretched scar after removal. a Note the linear appearing fiber arrangement after normal extraocular muscle resection, and b loss of the linear arrangement of collagen when tension is eliminated following scar excision. {Reprinted from Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333, with permission from American Association for Pediatric Ophthalmology and Strabismus [22]}

Fig. 23.25. Histologic study of scar segment shows wavy bundles of dense connective tissue (left). Normal extraocular muscle tendon histologic study after resection. Collagen bundles are larger and more regularly oriented (right). {Reprinted from Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333, with permission from American Association for Pediatric Ophthalmology and Strabismus [22]}

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riod of time and without a duction deficit, exploration of the previously operated muscle(s) for a possible stretched scar is probably not required. However, in patients with a duction deficit, we would advise exploration of the previously operated muscle, with repair of identified pathology, if found, always being indicated. Although it has been suggested that up to 50% of overcorrections may be due to stretched scar syndrome [22], the accuracy of this estimate is unclear. Several preventative techniques have been suggested to reduce the incidence of its occurrence. All involve attention to surgical details that are thought to enhance wound healing. The addition of a central locking bite to place a larger portion of the distal tendon in direct apposition to the sclera may have merit. Also, the surgeon should avoiding excessively tight sutures which could result in necrosis of the distal portion of tendon. The use of postoperative corticosteroids could in theory inhibit collagen synthesis and repair which could result in the development of a weaker bond between the muscle tendon and the sclera, though there is no direct evidence that this occurs with administration of topical corticosteroids. Avoidance of the hang-back approach to recession surgery, opting instead for direct suturing of the muscle to the sclera, has also been suggested as possibly being protective in at-risk patients. These tips may or may not be valid, and at present there is little scientific evidence to suggest that these modifications in surgical technique will be successful in reducing the risk of developing a stretched scar. While the role of scar stretching in strabismus requires further study, recognition that it may occur and that it may be associated with a large number of overcorrections is important. Fortunately, some of the tips recommended to theoretically reduce the occurrence of slipped scar syndrome are good general techniques that should be considered during strabismus surgery in all cases.

References 1. 2.

3. 4. 5.

6.

Parks MM, Bloom JN (1979) The “slipped” muscle. Ophthalmology 86:1389–1396 Bloom JN, Parks MM (1981) The etiology, treatment and prevention of the “slipped muscle”. J Pediatr Ophthalmol Strabismus 18:6–11 Plager DA, Parks MM (1988) Recognition and repair of the slipped rectus muscle. J Pediatr Ophthalmol Strabismus 25:270–274 Murray AD (1998) Slipped and lost muscles and other tales of the unexpected. Philip Knapp Lecture. J AAPOS 2:133–143 Knapp P (1978) Lost muscle. In: Symposium on strabismus. Transactions of the New Orleans Academy of Ophthalmology. CV Mosby, St. Louis, Mo., p 5 MacEwen CJ, Lee JP, Fells P (1992) Aetiology and management of the “detached” rectus muscle. Br J Ophthalmol 76:131–136

Chapter 23 7.

8.

9. 10.

11.

12.

13.

14. 15.

16. 17.

18.

19.

20.

21. 22. 23.

24.

Ward TP, Thach AB, Madigan WP Jr., Berland JE (1997) Magnetic resonance imaging in posttraumatic strabismus. J Pediatr Ophthalmol Strabismus 34:131–134 Raz J, Bernheim J, Pras E, Saar C, Assia EI (2002) Diagnosis and management of the surgical complication of postoperative “slipped” medial rectus muscle: a new “tendon step test” and outcome/results in 11 cases. Binocul Vis Strabismus Q 17:25–33 Mims JL 3rd (1992) Forming and teaching true knots for strabismus surgery. Ophthalmic Surg 23:477–481 Eitzen JP, Elsas FJ (1991) Strabismus following endoscopic intranasal sinus surgery. J Pediatr Ophthalmol Strabismus 28:168–170 Plager DA, Parks MM (1990) Recognition and repair of the “lost” rectus muscle. A report of 25 cases. Ophthalmology 97:131–136; discussion 136–137 Friendly DS, Parelhoff ES, McKeown CA (1993) Effect of severing the check ligaments and intermuscular membranes on medial rectus recessions in infantile esotropia. Ophthalmology 100:945–948 Greenwald M (1990) Intraoperative muscle loss due to muscletendon dehiscence. Proceedings of the 16th Annual Meeting of American Association of Pediatric Ophthalmology and Strabismus. Lake George, New York Kowal L, Wutthiphan S, McKelvie P (1998) The snapped inferior rectus. Aust N Z J Ophthalmol 26:29–35 Paysse EA, Saunders RA, Coats DK (2000) Surgical management of strabismus after rupture of the inferior rectus muscle. J AAPOS 4:164–167 Miller JM (1989) Functional anatomy of normal human rectus muscles. Vision Res 29:223–240 Trotter WL, Kaw P, Meyer DR, Simon JW (2000) Treatment of subtotal medial rectus myectomy complicating functional endoscopic sinus surgery. J AAPOS 4:250–253 Lenart TD, Reichman OS, McMahon SJ, Lambert SR (2000) Retrieval of lost medial rectus muscles with a combined ophthalmologic and otolaryngologic surgical approach. Am J Ophthalmol 130:645–652 Brooks SE, Olitsky SE, de BRG (2000) Augmented Hummelsheim procedure for paralytic strabismus. J Pediatr Ophthalmol Strabismus 37:189–195; quiz 226–227 Olitsky SE, Notaro S (2000) Anterior transposition of the inferior oblique for the treatment of a lost inferior rectus muscle. J Pediatr Ophthalmol Strabismus 37:50–51 Ludwig IH (1999) Scar remodeling after strabismus surgery. Trans Am Ophthalmol Soc 97:583–651 Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333 Nordstrom RE, Nordstrom RM (1986) Absorbable versus nonabsorbable sutures to prevent postoperative stretching of wound area. Plast Reconstr Surg 78:186–190 Elliot D, Mahaffey PJ (1989) The stretched scar: the benefit of prolonged dermal support. Br J Plast Surg 42:74–78

Chapter

Hemorrhage

24

24 24.1 Introduction Hemostasis is important in any surgical procedure. Minor hemorrhage, easily controlled by cautery, occurs during many strabismus operations, while severe hemorrhage is uncommon. Severe hemorrhage can result in alteration of expected postoperative ocular alignment, retinal detachment, and even blindness. Awareness of potential causes of serious hemorrhage during strabismus surgery and of risk factors can reduce the occurrence of serious intraocular and periocular hemorrhage during and after surgery.

24.2 Risk Factors Several subgroups of patients are at increased risk for significant hemorrhage during strabismus surgery. Patients with a bleeding diathesis and patients on anticoagulant medications are obvious risk groups. Despite this, hemorrhage is generally reasonably limited and easily controlled during strabismus surgery so that many surgeons do not ask patients to discontinue their anticoagulant medications prior to surgery. In a study of 108 adult patients undergoing strabismus surgery, hemorrhage significant enough to necessitate cautery to control bleeding to allow continuation of surgery occurred in 4 (14.8%) of 27 patients on anticoagulants compared to 1 (1.2%) of 81 patients who were not taking anticoagulants (unpublished data). Thus it is not unreasonable to recommend discontinuation of anticoagulants prior to strabismus surgery. The decision to discontinue anticoagulants prior to surgery depends on the complexity of the surgery, the health of the patient and the preference of the surgeon. The risk of health problems associated with temporary discontinuation of anticoagulant medications in patients with medical indications for these agents must be considered before making this recommendation. Patients undergoing reoperations, especially if there is extensive scarring, are at increased risk of developing significant hemorrhage. Patients undergoing complex operations with limited exposure of the surgical site may also be at increased risk of intraoperative hemorrhage. Examples include large recession and posterior fixation suture surgery, both of which require surgical manipulation in the orbit well beyond the comfortable range of 10–12 mm from the limbus. Potential

causes of hemorrhage in these cases include scleral perforation causing vitreous and/or retinal hemorrhage and disruption of anterior ciliary vessels and/or vortex veins.

24.3 Eyelid Hemorrhages Serious complications from eyelid hemorrhages are infrequent. Though not generally vision threatening, bruising of the eyelids following strabismus surgery can be alarming to patients because of both fear provoked by the appearance of the hemorrhage itself, and the potential negative social and vocational consequences associated with hemorrhage, which may prolong the time before a patient returns to work, or may lead to teasing at school in younger patients. The most common cause of eyelid hemorrhages following strabismus surgery is retrobulbar injection of anesthetic agents. Hemorrhages involving the eyelids can occur after both retrobulbar and peribulbar injection of anesthesia, but eyelid hemorrhages can also occur in patients who have not undergone retrobulbar or peribulbar injection. Patients may exhibit little or no bruising in the immediate perioperative period, developing mild to marked bruising of the lids during the first 24 h after surgery (>Fig. 24.1). Anticoagulant use may be associated with increased lid bruising. In addition to eyelid hemorrhages, buccal fat pad hemorrhage has been reported after retrobulbar injection in the absence of hemorrhage in the retrobulbar space [1].

Fig. 24.1. Eyelid hemorrhages following retrobulbar injection of anesthetic agent for strabismus surgery

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The occurrence of eyelid (and subconjunctival) hemorrhages can be reduced by use of a sub-Tenon’s block. A small incision is made in the inferotemporal or inferonasal quadrant through conjunctiva and Tenon’s fascia. A blunt-tipped cannula is then used to administer anesthetic into the posterior sub-Tenon’s space. The technique is well accepted for use in eye surgery and is well tolerated by patients [2]. Eyelid bruising can occasionally occur even after otherwise routine strabismus surgery under general anesthesia in patients who have not undergone a retrobulbar anesthetic block. We have seen this occur occasionally in patients following prolonged strabismus surgery, particular for complex reoperations associated with extensive scaring, such as repair of a slipped or lost muscles requiring extensive surgical manipulation. It is most likely to occur in our experience with surgery on the inferior rectus, inferior oblique or medial rectus muscles.

24.4 Orbital Hemorrhage Orbital hemorrhages can occur during surgery due to disruption of muscular arteries or vortex veins (see below), and most orbital hemorrhages occur as a result of local anesthesia administration. Though most available data on hemorrhages associated with local ocular anesthesia involve cataract surgery, the information is valid for similar injections administered for strabismus surgery. Retrobulbar hemorrhage has been reported to occur in between 1% and 3% of cases performed under retrobulbar anesthesia [3]. Peribulbar anesthesia has also been associated with retrobulbar hemorrhage and permanent vision loss [4]. In patients who we feel are at particularly high risk for developing retrobulbar hemorrhage, we often achieve ocular anesthesia and akinesia through a sub-Tenon’s block using a blunt-tipped cannula to minimize this risk. Though the risk of retrobulbar hemorrhage is lower with a sub-Tenon’s infusion, we have experienced one case of retrobulbar hemorrhage despite the use of this technique [5] and retrobulbar hemorrhage has been reported following use of this technique for cataract surgery as well [6]. Our patient was a 62-year-old woman who

Chapter 24

underwent infusion of 3 ml lidocaine (2%) into the posterior sub-Tenon’s space. The agent was infused through a small conjunctival/Tenon’s fascia incision in the inferonasal quadrant using a 19-gauge blunt-tipped cannula. Upon withdrawal of the cannula, the patient complained of severe pain and acute proptosis developed. The conjunctiva became immediately edematous and hemorrhagic and eyelid ecchymosis was noted. Her intraocular pressure became acutely elevated to 68 mmHg and fundus examination revealed pulsations of the central retinal artery. A lateral canthotomy was performed resulting in reduction of her intraocular pressure. Strabismus surgery was abandoned and the patient did well, recovering without loss of vision. She underwent uneventful strabismus surgery 2 weeks later. While the mechanism for the hemorrhage following sub-Tenon’s anesthetic infusion was unclear in this case, we postulated that the volume of the fluid infused behind the globe may have displaced and ruptured a sclerotic vessel, with resulting hemorrhage. We recommend infusion of the minimum volume of anesthetic agent required to accomplish surgery and recommend slow infusion of the agent under low injection pressure. Treatment of a retrobulbar hemorrhage is dependent on severity. If the intraocular pressure is not dangerously elevated and perfusion of the central retinal artery is not compromised, observation may be all that is warranted. Vision loss can occur due to both optic nerve compression and elevation of intraocular pressure. Simple measures that may be useful to control acute elevation of intraocular pressure include intermittent ocular massage, anterior chamber paracentesis, and administration of ocular hypotensive agents. Lateral canthotomy with or without inferior cantholysis may be required to control both intraocular and intraorbital pressure (>Fig. 24.2). Liu [7] described a simple technique for orbital decompression to treat severe retrobulbar hemorrhage not responsive to other measures such those described above. An inferonasal incision is made through the conjunctiva and Tenon’s capsule. A hemostat is then advanced 20 mm into the orbit along the medial orbital floor. Downward pressure is then applied on the hemostat to break the orbital floor and adjacent maxillary sinus mucosa, entering the maxillary sinus (>Fig. 24.3).

Fig. 24.2a,b. Lateral canthotomy for treatment of acute retrobulbar hemorrhage. a A hemostat is placed across the lateral canthus and removed after 30–60 s and the lateral canthus is then cut with scissors. b An inferior cantholysis can be performed if additional measures are needed

 

24.5  Muscle Hemorrhage Fig. 24.3. Simple technique of orbital decompression for retrobulbar hemorrhage not responsive to other measures. A hemostat is placed into an incision in the inferonasal quadrant and advanced 20 mm along the medial aspect of the orbital floor. The hemostat is then used to break the floor of the orbit to enter the maxillary sinus

24.5 Muscle Hemorrhage Hemorrhage from muscular arteries has been reported. We performed bilateral inferior oblique myectomy on a child several years ago. Two hemostats were placed across the inferior oblique muscle and the muscle segment between the clamps was removed in each eye. Cautery, which is typically applied to the cut edges of the muscle prior to removal of the hemostats, was inadvertently omitted on one eye. The proximal aspect the inferior oblique muscle was then tucked into Tenon’s capsule and the conjunctiva closed. Upon reemergence from anesthesia, the patient coughed and severe proptosis of the right eye developed without obvious external hemorrhage. The intraocular pressure was markedly elevated and pulsations of the central retinal artery were noted. A lateral canthotomy was performed and ocular hypotensive agents were administered. The surgical wound was opened and the proximal end of the hemorrhaging inferior oblique muscle was identified with some difficulty and cautery applied. Other than ocular adnexal bruising, the remainder of his recovery was routine and the patient did well without suffering loss of vision. Delayed retrobulbar hemorrhage has also been reported. Cates and coworkers [8] reported the case of a 4-year-old boy who developed a slipped medial rectus muscle in his right eye as a result of an orbital hemorrhage. The child had undergone medial rectus muscle recession in both eyes to a position 10.5 mm posterior to the limbus. The surgery was uncomplicated and good hemostasis was maintained throughout the procedure. The patient experienced rapid swelling, bruising of the eyelids, and periocular pain that began several hours after surgery. The surgeon was not contacted and when the patient was

seen 1 week later a large secondary exotropia was present and moderate limitation of adduction noted. Reoperation revealed a pseudo-tendon of the medial rectus muscle that remained partially attached 10.5 mm posterior to the limbus. The muscle itself was found 20 mm posterior to the limbus. It was advanced to a position 5.5 mm posterior to the limbus and the child ultimately did well. The authors postulated that inadequate cautery to muscular arteries in this active child may have resulted in the acute hemorrhage which occurred with sufficient force to detach the muscle from the globe. They suggested that if a hang-back suture had been used, the muscle position probably would not have been altered by the hemorrhage. Todd and coworkers [9] reported a case of delayed orbital hemorrhage that did not develop until approximately 36 h after an otherwise routine horizontal recess and resect operation. During surgery, bleeding from the medial rectus muscle was noted, though hemostasis was achieved with cautery. The patient presented for follow-up with marked proptosis, count fingers vision, and a relative afferent pupillary defect. Computed tomography scan revealed a massively enlarged medial rectus muscle consistent with a muscle hematoma. A lateral canthotomy was performed and the muscle explored. A pulsatile bleeding artery was identified at the proximal muscle stump. The vessel was cauterized and the muscle sutured to the sclera. The patient was treated with oral steroids for 5 days and subsequently recovered visual acuity to the level of 20/20 and had good ocular alignment. The authors postulated that excessive coughing, which occurred on the first postoperative day, had stimulated the hemorrhage. In support of this theory, they noted that spontaneous orbital hemorrhage has occasionally been reported following straining [10]. Periorbital hemorrhages have also been reported following extensive coughing [11].

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In a very unusual case, Carden and coworkers [12] reported the development of bilateral orbital hemorrhages during strabismus surgery which was being performed under general anesthesia. The patient had received no retrobulbar or peribulbar anesthesia. The procedure was uncomplicated until the surgeons noted that both ocular globes had become firm to palpation toward the end of the case. Proptosis and hemorrhaging from the conjunctival wounds developed. Intraocular pressure increased to 40 mmHg in both eyes. The patient’s blood pressure was well controlled throughout the procedure and there was no history of bleeding diathesis. The patient had previously undergone three other uncomplicated nonophthalmologic surgical procedures with no history of excessive bleeding. She was managed with ocular hypotensive agents and her intraocular pressure decreased after 2 h of treatment. Bleeding from the surgical incisions ceased spontaneously. Investigation for a bleeding diathesis did not occur until approximately 2 weeks after surgery, at which time the evaluation was unremarkable. Unknown to her surgeons, she had been taking odorless garlic tablets prescribed by a naturopath and she had consumed five tablets (approximately 5 g of equivalent fresh bulb) the day before surgery. She had also consumed garlic regularly prior to surgery, but had not consumed any since surgery. The surgeons postulated that the garlic supplements were responsible for her bleeding diathesis. Garlic is known to have anticoagulant properties by inhibition of platelet aggregation. Because of potentially unpredictable hemostasis following garlic supplement ingestion, patients should cease ingestion of garlic tables at least 7 days prior to surgery. Bleeding has been reported in association with garlic ingestion during other surgical procedures as well, including transurethral resection of the prostate [13] and mammoplasty [14]. There is also a report of a spontaneous epidural hematoma in a patient taking garlic supplements [15]. Surgeons should be aware that patients may be taking naturopathic agents which could interact with other medications and/or be associated with intraoperative or perioperative hemorrhage. Both ginkgo balboa and ginseng, in addition to garlic supplements, have been associated with bleeding [16].

24.6 Vortex Vein Hemorrhage Damage or disruption of the four vortex veins is uncommon during strabismus surgery despite the fact that vortex veins are encountered frequently during strabismus surgery. Damage to a vortex vein is unlikely to occur during routine surgery by a surgeon familiar with the relevant anatomy. Disruption of a vortex vein is most likely to occur during reoperations in which there is extensive scarring and tissue distortion, displacing one or more vortex veins to an unusual anatomic location. Vortex veins are generally quite elastic and forgiving, rarely rupturing if moderately stretched during surgery. Bleeding from a vortex vein can be pronounced, but easily controlled by pressure through temporary intraoperative packing of the operative site. Surgery can continue once bleeding has ceased, but if the adjacent tissues have become bloodstained and make delineation of tissue planes difficult, further surgery should be postponed

Chapter 24

until a later date. Data on complications associated with vortex vein damage following scleral buckling surgery are available, and may be similar to complications of vortex vein damage following strabismus surgery, though published data about this condition following strabismus surgery are not available. Doi and coworkers [17] reported an increased frequency of ­elevated intraocular pressure, vitreous hemorrhage, choroidal detachment, and vitreous opacification following scleral buckling surgery in which a vortex vein had been damaged.

24.7 Subconjunctival Hemorrhage Subconjunctival hemorrhages occur following almost all strabismus operations. They can be particularly alarming to patients because they tend to progress in the first 24–48 h after surgery. The family who has been advised that increasing redness can be a sign of postoperative infection may call with concerns about an expanding subconjunctival hemorrhage. Careful postoperative explanation about the benign nature of subconjunctival hemorrhage can reduce patient and parent concerns after surgery. Warning patients about the potential for a subconjunctival hemorrhage to spread and about possible green and yellow discoloration of the hemorrhage that occurs during breakdown of hemoglobin as the hemorrhage resolves is important. The occurrence of subconjunctival hemorrhages can be reduced by use of cautery to the conjunctiva prior to sub-Tenon’s anesthesia infusion in patients undergoing cataract surgery [18], though it is likely that this technique would result in a reduction of subconjunctival hemorrhages in patients undergoing strabismus surgery.

24.8 Intraocular Hemorrhage Intraocular hemorrhage can occur at several stages during strabismus surgery. Awad and coworkers [19] reported four patients who experienced anterior chamber collapse and hyphema following placement of traction sutures at the limbus during strabismus surgery. They abandoned surgery on these patients until the hyphema had cleared and later surgery was uneventful. None of the patients experienced loss of vision. Both localized [19] and severe [19–21] vitreous hemorrhage have been reported in association with eye wall perforation during strabismus surgery. Late-onset vitreous hemorrhage that was believed to be related to scleral perforation during previous strabismus surgery has also been reported [22].

References 1. 2.

Kuchtey R, Perry JD, Lerner L (2004) Buccal fat pad hemorrhage after retrobulbar injection. Am J Ophthalmol 137:1131–1132 Kumar CM, Williamson S, Manickam B (2005) A review of subTenon’s block: current practice and recent development. Eur J Anaesthesiol 22:567–477

  3.

4.

5.

6. 7. 8.

9. 10. 11.

12. 13.

Morgan CM, Schatz H, Vine AK et al (1988) Ocular complications associated with retrobulbar injections. Ophthalmology 95:660–665 Puustjarvi T, Purhonen S (1992) Permanent blindness following retrobulbar hemorrhage after peribulbar anesthesia for cataract surgery. Ophthalmic Surg 23:450–452 Olitsky SE, Juneja RG (1997) Orbital hemorrhage after the administration of sub-Tenon’s infusion anesthesia. Ophthalmic Surg Lasers 28:145–146 Rahman I, Ataullah S (2004) Retrobulbar hemorrhage after subTenon’s anesthesia. J Cataract Refract Surg 30:2636–2637 Liu D (1993) A simplified technique of orbital decompression for severe retrobulbar hemorrhage. Am J Ophthalmol 116:34–37 Cates CA, Hodgkins PR, Morris RJ (2000) Slipped medial rectus muscle secondary to orbital hemorrhage following strabismus surgery. J Pediatr Ophthalmol Strabismus 37:361–362 Todd B, Sullivan TJ, Gole GA (2001) Delayed orbital hemorrhage after routine strabismus surgery. Am J Ophthalmol 131:818–819 Sullivan TJ, Wright JE (2000) Non-traumatic orbital haemorrhage. Clin Exp Ophthalmol 28:26–31 Paysse EA, Coats DK (1998) Bilateral eyelid ecchymosis and subconjunctival hemorrhage associated with coughing paroxysms in pertussis infection. J AAPOS 2:116–119 Carden SM, Good WV, Carden PA, Good RM (2002) Garlic and the strabismus surgeon. Clin Exp Ophthalmol 30:303–304 German K, Kumar U, Blackford HN (1995) Garlic and the risk of TURP bleeding. Br J Urol 76:518

References 14. Burnham BE (1995) Garlic as a possible risk for postoperative bleeding. Plast Reconstr Surg 95:213 15. Rose KD, Croissant PD, Parliament CF, Levin MB (1990) Spontaneous spinal epidural hematoma with associated platelet dysfunction from excessive garlic ingestion: a case report. Neurosurgery 26:880–882 16. Ang-Lee MK, Moss J, Yuan CS (2001) Herbal medicines and perioperative care. J Am Med Assoc 286:208–216 17. Doi N, Uemura A, Nakao K (1999) Complications associated with vortex vein damage in scleral buckling surgery for rhegmatogenous retinal detachment. Jpn J Ophthalmol 43:232–238 18. Chung RS, Chua CN (2005) Reduction of subconjunctival hemorrhage with sub-Tenon’s anesthesia. J Cataract Refract Surg 31:2031 19. Awad AH, Mullaney PB, Al-Hazmi A et al (2000) Recognized globe perforation during strabismus surgery: incidence, risk factors, and sequelae. J AAPOS 4:150–153 20. Greenberg DR, Ellenhorn NL, Chapman LI, Miller MT, Folk ER (1988) Posterior chamber hemorrhage during strabismus surgery. Am J Ophthalmol 106:634–635 21. Arnold RW, Barnett M, Limstrom SA, Swanson D (2001) Vision loss associated with a stiff neck complicating strabismus surgery. Binocul Vis Strabismus Q 16:181–186 22. Basmadjian G, Labelle P, Dumas J (1975) Retinal detachment ­after strabismus surgery. Am J Ophthalmol 79:305–309

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Adherence and Adhesion Syndromes

25

25 Scar formation occurs following all strabismus procedures. The formation of an adequate scar, in fact, is required for normal postoperative healing. However, abnormal scar formation, or normal scar formation that occurs after unplanned intraoperative events, may lead to undesirable surgical outcomes. Adherence and adhesion syndromes occur following strabismus surgery and are due to fibrous scar formation that alters postoperative alignment and/or limits ocular rotations. This chapter will review these syndromes and discuss their prevention and treatment.

25.1 Fat Adherence Syndrome The term fat adherence syndrome refers to a progressive restrictive strabismus associated with the intrusion of extraconal orbital fat into the sub-Tenon’s or episcleral space during surgery or following trauma. Exposed extraconal fat that enters the episcleral space can come into contact with the extraocular muscles, the sclera and/or other orbital connective tissue ­elements. A fibrous scar can develop which is attached to the orbital periosteum. This scar then contracts and leads to progressive strabismus with inhibition of ocular movement. The entrance of extraconal fat into the episcleral space occurs due to a disruption in posterior Tenon’s capsule, which normally acts as a barrier to fat entering this location (>Fig. 25.1). Fat adherence syndrome may occur following strabismus surgery, scleral buckling surgery, and other surgeries when violation of posterior Tenon’s capsule occurs. The condition may also occur as a result of orbital trauma. For the strabismus surgeon, the condition most commonly occurs following surgery on the inferior oblique muscle. As such, the typical motility disorder usually consists of a progressive hypotropia, an inability to ­fully elevate the involved eye and positive forced duction testing on attempted passive elevation of the globe. The fat adherence syndrome was first described by Parks in 1972 [1]. Initially, he stated that the cause of the disorder was an adherence between the globe and orbital tissue to orbital fat which occurred following a violation of posterior Tenon’s capsule. Later, he suggested the cause was due to contracture of fibrous connective tissue found within the orbit secondary to inflammation. Parks felt that trauma to the orbital fat was necessary for the development of fat adherence syndrome but the orbital fat was not by itself the cause.

It has been difficult to explore the actual etiology of this syndrome. Attempts to produce an animal model of fat adherence syndrome have not been successful. Brooks and coworkers [2] could not reproduce fat adherence syndrome in a pig model in spite of severe surgical and thermal trauma to posterior Tenon’s capsule and orbital fat. Kerr [3] was able to produce a restrictive strabismus in a rabbit model by securing fat autographs between the inferior rectus muscle and the periosteum of the inferior orbital rim. However, there may be fundamental differences in the orbital anatomy and healing process that occurs in the pig orbit compared to humans. In addition, although the rabbit model can produce a restrictive strabismus that resembles that seen in fat adherence syndrome, the rabbit orbit does not contain a large amount of fat and therefore may not serve as an ideal model. Although the exact cause of fat adherence syndrome remains unknown, it seems clear from clinical and anecdotal evidence that violation of posterior Tenon’s ­capsule and trauma to the extraconal fat is necessary for the development of the syndrome. The rabbit model described above has suggested this as well. The amount of fat introduced in the experimental model correlated with the degree of restriction that later developed. Most ophthalmologists have interpreted the clinical evidence to suggest that poor surgical technique is a major cause of the development of fat adherence syndrome and provides the violation of Tenon’s capsule and trauma to extraconal fat needed for fat adherence syndrome to develop [4]. However, this view may be unfair, as violation of posterior Tenon’s capsule can occur even with well-performed surgery by expert surgeons.

25.2 Incidence Parks [1] reported an incidence of fat adherence syndrome of 2% in patients undergoing inferior oblique muscle surgery in his original series. The incidence of fat adherence syndrome is unknown today. The number of cases appears to have decreased, most likely due to the recognition of the condition, and better understanding of the potential consequences of violating posterior Tenon’s capsule during surgery. Improvements in surgical techniques probably also contribute significantly to a reduction in the incidence of this complication. Some cases of restrictive strabismus following retinal surgical procedures occur due to fat adherence syndrome. Hwang and Wright [5]

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Chapter 25

Fig. 25.1. Fat adherence syndrome occurs due to the intrusion of extraconal fat into the episcleral space through a disruption in posterior Tenon’s capsule

found an incidence of almost 50% in a series of patients with persistent strabismus following retinal surgery. Fat adherence syndrome has also been reported following blepharoplasty and orbital trauma [6]. The common feature in all of these cases is trauma to posterior Tenon’s capsule with prolapse of and damage to extraconal fat.

25.3 Prevention The best method to prevent the development of fat adherence syndrome is to avoid damage to posterior Tenon’s capsule during strabismus surgery. This is especially true during inferior oblique surgery, where damage to posterior Tenon’s capsule is most likely to occur. Direct visualization of the posterior bor-

der of the inferior oblique muscle during its isolation can help to reduce the risk of penetrating Tenon’s capsule (>Fig. 25.2). Blind sweeps of the inferotemporal quadrant to isolate the inferior oblique muscle are discouraged. Overhead lighting directed into the operative space is helpful. Some surgeons find use of a headlamp helpful during surgery on the inferior oblique muscle. In addition, overly aggressive dissection posterior to the inferior oblique muscle should be avoided. If a defect in posterior Tenon’s capsule is noted during surgery, it should be treated. It may be possible to reposition small amounts of orbital fat that protrude through a rent in posterior Tenon’s capsule back into the extraconal space followed by closure of the rent. When this is not possible, as for example when a large amount of extraconal fat has entered the episcleral space, we recommend placing a hemostat across the fat at the opening of the defect and excising that portion of the fat that has pro-

 

25.5  Miscellaneous Adhesion Syndromes

[9] reported the use of botulinum toxin in the early postoperative period of a patient who developed fat adherence syndrome following inferior oblique surgery for the treatment of a superior oblique palsy. They suggested that injection before scar tissue could fully develop was a key element in the success they had in the management of their patient. Yamada and Shinoda [10] combined strabismus surgery and placement of an amniotic membrane to prevent re-formation of adhesions to successfully treat fat adherence syndrome in a patient who had previously undergone retina surgery.

25.5 Miscellaneous Adhesion Syndromes Due to Strabismus Surgery Fig. 25.2. Identification of the posterior border of the inferior oblique muscle prior to isolation of the muscle on a hook may help to reduce the risk of violating posterior Tenon’s capsule

truded into the operative site. The defect in Tenon’s capsule can then be sutured closed using absorbable sutures. The use of antimetabolites is not warranted. Brooks and coworkers [7] investigated the prophylactic use of intraoperative mitomycin-C in a rabbit model of fat adherence syndrome to prevent the development of restrictive scar formation. They could find no significant difference between the treated and untreated groups. They also found that longer exposure to mitomycin-C resulted in an increase in the postoperative inflammatory response and was associated with an increase in restriction.

25.5.1 Adhesion Syndrome Following Superior Oblique Tendon Expander Surgery Wilson and co-workers [11] reported two patients who developed diplopia in the reading position following insertion of a silicone superior oblique tendon expander for the treatment of unilateral Brown syndrome. In both cases, forced duction testing to down gaze demonstrated restriction and surgical exploration revealed adhesions that prevented normal movement of the superior oblique tendon beneath the superior rectus muscle. Following removal of the silicone band, forced ductions became normal and down gaze was improved Restrictive strabismus may also occur if the sub-Tenon’s space is violated at the time of expander insertion [12].

25.4 Treatment Surgical treatment of a patient with significant fat adherence syndrome can be difficult. The goal of treatment is to align the eyes in the primary position and restore the ocular movements as much as possible. Most reports in the literature support the notion that a return of normal ocular rotations is not possible in most cases. Burton and coworkers [8] reported 14 cases of fat adherence syndrome that underwent attempted surgical treatment. Their results agreed with the generally held belief that surgery is difficult and that outcomes are often poor. They suggested that patients be given realistic expectations as to their final possible outcome. In most cases, treatment involves disruption of the adhesions to minimize restriction. Simultaneous surgery on the extraocular muscles is almost always also necessary. For example, if there is a hypotropia due to longstanding restrictive forces exist in the inferior orbit, surgery to release the adhesions will usually have a limited impact on ocular alignment. Instead, the inferior rectus muscle must usually be recessed to achieve significant improvement. The use of temporary postoperative traction sutures (Chap. 15) may be beneficial to reduce the risk of recurrent adhesions in these cases. Other treatments have been reported with varying levels of success. Most reports involve isolated cases and interpretation of these results should bear this in mind. Ozkan and coworkers

25.5.2 Inferior Oblique Inclusion Syndrome Price [13] described an L-deformity of the inferior oblique muscle which can occur following lateral rectus muscle surgery due to deep passage of a muscle hook in an attempt to hook the lateral rectus muscle with inadvertent, simultaneous hooking of the inferior oblique muscle or by failure to sever the fascial attachments between the inferior oblique muscle and the lateral rectus muscle. The condition is more likely to occur following lateral rectus resection than with lateral rectus muscle recessions [13, 14] (>Fig. 25.3). Postoperatively, patients may have a residual esotropia or exotropia and typically exhibit a hypotropia of the involved eye with limitation of elevation. The condition can sometimes mimic Brown syndrome. Price [13] recommended several techniques to avoid inclusion of the inferior oblique muscle during lateral rectus muscle surgery, noting that the surgeon was less likely to inadvertently hook the inferior oblique muscle when the hook was passed from above. He noted that even this maneuver sometimes resulted in inadvertent hooking of the inferior oblique muscle, however. Helveston and coworkers [14] recommended that surgeons could avoid inadvertent inferior oblique inclusion by inspecting the global surface of the lateral rectus muscle and freeing any inferior oblique attachments prior to reattaching

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Fig. 25.3. Inferior oblique adhesion syndrome. Note dense adhesions between the inferior border of the lateral rectus muscle and the inferior oblique muscle which has been displaced anteriorly

the lateral rectus muscle to the globe during surgery to recess or resect the lateral rectus muscle. Price [13] noted that repair of strabismus caused by inferior oblique inclusion in the lateral rectus muscle insertion was difficult. He recommended releasing adhesions between the inferior oblique and lateral rectus muscles until forced duction testing was normal. He further recommended that prolapsed orbital fat and scarring around Tenon’s capsule is often present and should be excised. Helveston and coworkers [14] reported that most patients had a persistent vertical deviation even after adhesions between the lateral rectus and inferior oblique muscles were freed. A recession of the inferior rectus muscle was usually required to correct the hypotropia, because secondary contraction of the inferior rectus muscle during a long-standing hypotropia will not be corrected by release of the adhesions alone.

25.5.3 J-Deformity of a Rectus Muscle Price [13] described J-deformity of a rectus muscle that he believed occurred because of failure to adequately dissect the surrounding Tenon’s capsule during rectus muscle surgery. He believed that contracture of Tenon’s capsule could advance the belly of the muscle anteriorly toward the limbus causing the recurrence of strabismus, limited ductions, and a characteristic J-deformity of the muscle. We have not treated a patient with this J-deformity of a rectus muscle.

Chapter 25

in the development of restrictive strabismus. Treatment is often difficult and additional surgery can further compound the problem by inciting more fibrovascular scar formation. Excessive scarring of the conjunctiva may lead to a duction deficit. This may occur secondary to shortening of the conjunctiva or due to scarring between the conjunctiva and the extraocular muscle(s). Often the tightness of the conjunctiva can be visualized clinically when the patient attempts to move his or her eyes. It can also be demonstrated with forced duction testing before or during surgery, which will demonstrate restriction to passive movement of the eyes. Extensive scarring between Tenon’s fascia and the extraocular muscles can also be similarly demonstrated. Often both the conjunctiva and Tenon’s fascia are involved. At the time of surgery, the restrictive forces should be eliminated or reduced whenever possible. Once forced duction testing indicates that this goal has been obtained, the next step involves reducing the chance of recurrent scarring, if possible. This can be accomplished by recessing the conjunctiva if it is contracted and is wholly or partly responsible for the restriction (Chap. 8). The use of medications to alter scar formation, such as mitomycin-C and 5-fluorouracil [15], and the application of Seprafilm®, a bioabsorbable membrane composed of sodium hyaluronate and carboxymethylcellulose, have been studied in animals [16], but have not been shown to be effective for routine use in human restrictive strabismus. Adherence and adhesion syndromes can occur with any strabismus surgery, but are most likely to occur with surgery involving the inferior oblique muscles. Treatment can be difficult and the surgical outcome is often suboptimal. In theory, most cases of fat adherence syndrome should be avoidable through knowledge of the relevant surgical anatomy and attention to surgical technique. Adherence syndromes such as that which may occur following placement of a silicone expander in the superior oblique tendon and after inadvertent inclusion of the inferior oblique muscle in the lateral rectus muscle insertion likewise are probably avoidable in most, though not all, cases.

References 1.

2.

3. 4.

25.5.4 Scarring of Tenon’s Capsule and Conjunctiva Scarring of the conjunctiva and Tenon’s capsule following strabismus surgery is inevitable, but generally mild. Occasionally scarring of these tissues will be extensive and can result

5.

6.

Parks MM (1972) The weakening surgical procedures for eliminating overaction of the inferior oblique muscle. Am J Ophthalmol 73:107–122 Brooks SE, Yu JC, Preston D, Johnson MH (1998) Restricted ocular motility after orbital trauma – studies with an animal model. J AAPOS 2:246–252 Kerr NC (2004) Fat adherence syndrome: an animal model. J AAPOS 8:349–356 Helveston EM, Haldi BA (1976) Surgical weakening of the inferior oblique. Int Ophthalmol Clin 16:113–126 Hwang JM, Wright KW (1994) Combined study on the causes of strabismus after the retinal surgery. Korean J Ophthalmol 8:83–91 Jameson NA, Good WV, Hoyt CS (1992) Fat adherence simulating inferior oblique palsy following blepharoplasty. Arch Ophthalmol 110:1369

  7.

Brooks SE, Ribeiro GB, Archer SM, Elner VM, Del Monte MA (1996) Fat adherence syndrome treated with intraoperative mitomycin-C: a rabbit model. J Pediatr Ophthalmol Strabismus 33:21–27 8. Burton B, Dawson E, Lee J (2004) Adherence syndrome following inferior oblique surgery: management and outcome of 14 cases. Strabismus 12:169–174 9. Ozkan SB, Kir E, Dayanir V, Dundar SO (2003) Botulinum toxin A in the treatment of adherence syndrome. Ophthalmic Surg Lasers Imaging 34:391–395 10. Yamada M, Shinoda K, Hatakeyama A, Nishina S, Mashima Y (2001) Fat adherence syndrome after retinal surgery treated with amniotic membrane transplantation. Am J Ophthalmol 132:280–282 11. Wilson ME, Sinatra RB, Saunders RA (1995) Downgaze restriction after placement of superior oblique tendon spacer for Brown syndrome. J Pediatr Ophthalmol Strabismus 32:29–34; discussion 35–36

References 12. Pollard ZF, Greenberg MF (2000) Results and complications in 66 cases using a silicone tendon expander on overacting superior obliques with A-pattern anisotropias. Binocul Vis Strabismus Q 15:113–120 13. Price R (1976) Role of Tenon’s capsule in postoperative restrictions. Int Ophthalmol Clin 16:197–207 14. Helveston EM, Alcorn DM, Ellis FD (1988) Inferior oblique inclusion after lateral rectus surgery. Graefes Arch Clin Exp Ophthalmol 226:102–105 15. Mora JS, Sprunger DT, Helveston EM, Evan AP (1997) Intraoperative sponge 5-fluorouracil to reduce postoperative scarring in strabismus surgery. J AAPOS 1:92–97 16. Özka S, Kır E, Culhac N, Dayanır V (2004) The effect of seprafilm on adhesions in strabismus surgery – an experimental study. J AAPOS 8:46–49

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Complications Involving the Ocular Adnexa

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26

26 Serious complications involving the ocular adnexa are unusual following strabismus surgery. However, noticeable changes in the eyelids are a frequent source of concern for patients after strabismus surgery, though concern is usually greater in the immediate than in the later postoperative period. It is helpful to document obvious abnormalities and asymmetry of the eyelids prior to surgery. This documentation can be comforting to patients who first become aware of asymmetry or abnormalities in their own anatomy after surgery, a time when patients tend to look very critically at their eyes. Unless the surgeon has pointed out preexisting abnormalities to the patient before surgery, the patient may feel that the surgeon and the surgery are responsible for the findings. This can be a source of significant concern for patients and for strabismus surgeons alike. For example, dehiscence of the levator muscle of the upper eyelid, especially when asymmetric, is not infrequently first noticed by patients following strabismus surgery. Though we are generally very careful to make note of preexisting eyelid problems, occasionally we have found ourselves in the position of trying to explain the presence of pre­existing eyelid abnormalities that we did not note prior to surgery. Examination of the patient’s driver’s license photograph or other preoperative photographs may allow an easy means of demonstrating to the patient that the eyelid feature they find objectionable was actually present prior to surgery.

gery. Both eyelid retraction and advancement can occur. Eyelid advancement is usually better tolerated than eyelid retraction, unless the advancement is marked, and particularly if it involves the upper eyelid. Bothersome alteration of eyelid position is less likely to occur following recessions and resections of 5 mm or less. Patients who are at greatest risk of developing eyelid retraction are those undergoing very large recessions, especially if undergoing surgical repair of restrictive strabismus, such as thyroid-related ophthalmopathy. Retraction of the lower eyelid following inferior rectus recession is not uncommon (>Fig. 26.1). Lower eyelid retraction may occur following recession of the inferior rectus muscle due to anatomic connections between the inferior rectus muscle and the capsulopalpebral fascia and the inferior tarsal muscle. Pacheco and coworkers [1] reported that 94% of patients who underwent an inferior rectus muscle recession developed lower eyelid retraction. They believed that approximately 0.5 mm of lower eyelid retraction would occur with each 3 mm of inferior rectus muscle recession. According to Meyer and coworkers [2], lower eyelid retraction can occasionally be associated with lagophthalmos and corneal exposure. Several techniques to reduce or eliminate the occurrence of lower eyelid retraction following inferior rectus muscle recession have been proposed. Helveston [3] recommended generous dissection around the inferior rectus muscle in an attempt

26.1 Eyelid Retraction and Advancement Following Vertical Rectus Muscle Surgery The orbital aspect of the sheath of the superior rectus muscles is adherent to the internal surface of the sheath of the levator palpebrae superioris muscle of the upper eyelid (Chap. 1). The close association of these two structures through their fascial sheaths accounts for the cooperative action seen during contraction of these two muscles, such as depression of the upper eyelid with down gaze. Likewise, similar connections exist between the inferior rectus muscle and the lower eyelid retractors. The surgeon must be aware of these connections because they can have important implications for the patient following surgery on the vertical rectus muscles. Postoperative alteration of the position of the upper and lower eyelids is the most common eyelid abnormality that occurs following strabismus sur-

Fig. 26.1. Marked lower eyelid retraction following a large recession of the inferior rectus muscle to treat hypotropia in a patient with thyroidrelated ophthalmopathy

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to sever fascial connections between the inferior rectus muscle and the lower eyelid retractors. Care should be taken during posterior dissection of the attachments around the inferior rectus muscle not to disturb the vortex veins that are usually found adjacent to the medial and lateral borders of the inferior rectus muscle and to avoid intrusion into the surrounding extraconal fat. Advancement of the capsulopalpebral head and securing it to the inferior rectus muscle with sutures has been advocated as a means to mitigate lower eyelid retraction [4, 5]. Pacheco and co-workers [1] recommended suspension of the capsulopalpe-

Chapter 26

bral head from the inferior rectus muscle insertion utilizing a separate adjustable suture (>Fig. 26.2). Using this technique, the surgeon is able to separately adjust the position of the lower eyelid after ocular alignment has been adjusted. We have found this procedure useful in patients with thyroid-related ophthalmopathy when undergoing large inferior rectus muscle recessions. When using the technique reported by Pacheco and coworkers [1] we have found it important to postpone conversion of the inferior rectus muscle sutures to a permanent knot until after the eyelid position has been adjusted, because adjustment of the eyelid position can alter ocular alignment via remain-

Fig. 26.2a–c. Placement of an adjustable suture on the inferior rectus muscle and lower eyelid retractors to allow adjustment of both after recession of the inferior rectus muscle. a Identification and dissection of the capsulopalpebral head, b placement of suture in the capsulopalpebral head and in the inferior rectus muscle, and c suspension of both adjustable sutures from the original insertion. Adjustment of the lower eyelid position is deferred until optimal ocular alignment has been achieved

 

ing attachments between the inferior rectus muscle and eyelid retractors. A compromise is sometimes necessary, preventing optimal adjustment of eyelid position. The techniques outlined above typically result in improvement, but not normalization of the lower eyelid position. Additionally, they are less likely to be effective with larger inferior rectus muscle recessions, particularly if significant restriction is present. Meyer and coworkers [2] reported a technique to address lower eyelid retraction at the time of inferior rectus muscle recession. They referred to the technique as primary infratarsal lower eyelid retractor lysis. Unlike other procedures which are designed to counteract the posterior movement of the capsulopalpebral head caused by inferior rectus muscle recession, their procedure was designed to reduce or eliminate

Fig. 26.3. Primary infratarsal lower eyelid retractor lysis. Top: horizontal incision through conjunctiva and lower eyelid retractors. Mid­ dle: lysis of the conjunctiva and lower eyelid retractors medially and laterally. Bottom: blunt dissection using a cotton-tipped applicator to further recess the eyelid retractors. {Reprinted from Meyer DR, Simon JW, Kansora M (1996) Primary infratarsal lower eyelid retractor lysis to prevent eyelid retraction after inferior rectus muscle recession. Am J Ophthalmol 122:331–339, copyright 1996, with permission from Elsevier [2]}

26.2  Aberrant Regeneration – Third Cranial Nerve

traction on the capsulopalpebral head at the level of the tarsus and adjacent eyelid connective tissues, thus preventing lower eyelid retraction, rather than attempting to counteract it. They reported use of this technique during inferior rectus muscle recession to treat hypotropia due to thyroid-related ophthalmopathy, blow out fracture, and orbital fibrosis. Following inferior rectus muscle recession, the eyelid is retracted anteriorly and superiorly using a 4–0 silk suture placed through the central portion of the eyelid margin (>Fig. 26.3). An infratarsal incision is made through the conjunctiva and through the lower eyelid retractors 3–4 mm below the inferior tarsal border. The infratarsal incision is extended medially and laterally after spreading in the plane between the lower eyelid retractors and orbital septum on one side and the orbicularis muscle on the other side. Maintaining traction on the eyelid margin and on the conjunctival/lower eyelid retractors, a cotton-tipped applicator is used to bluntly dissect inferiorly between the orbicularis muscle and the orbital septum, allowing the conjunctiva, lower eyelid retractors, and orbital septum to maximally recess. The incision is left to heal by primary intention. At the conclusion of the case, antibiotic ointment is placed in the eye and the lid suture is taped to the forehead under slight upward tension. The lid suture is removed 1–5 days later. Mild symblepharon formation was reported in several patients following the procedure, but was easily managed. Significant upper and lower eyelid retraction and advancement can be corrected postoperatively if attempts to prevent it during strabismus surgery are not fully successful. This is most likely to be required following large resections and recessions, especially if restrictive strabismus is present. Upper and lower eyelid retraction can be managed using oculoplastic surgery techniques [6]. Occasionally, we have made use of the normal fascial attachments between the vertical rectus muscles and the eyelid retractors to create intentional alterations in the position of the eyelids. For example, if a patient undergoing a vertical rectus muscle resection has preexisting retraction of the ipsilateral eyelid, care will be taken to minimize dissection of the capsulopalpebral attachments between the upper eyelid and the superior rectus muscle. This will result in a larger degree of upper eyelid advancement with resulting improvement of the eyelid retraction. A patient with mild ptosis of the upper eyelid who is undergoing a superior rectus muscle recession can achieve improvement of their ptosis by minimizing dissection of the capsulopalpebral attachments during surgery.

26.2 Aberrant Regeneration of the Third Cranial Nerve Surgery to correct a vertical and/or horizontal strabismus in patients with aberrant regeneration following a third nerve palsy can produce some dramatic and unpredictable changes in eyelid position and function. Patients undergoing strabismus surgery in this setting should be advised of this potential complication and made aware of the fact that eyelid surgery may be required to address the problem postoperatively.

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26.3 Eyelid Changes Following Horizontal Rectus Muscle Surgery Several unique surgical situations and complications have been shown to alter the width of the eyelid fissures following horizontal rectus muscle surgery. The lid fissures have been noted to widen in patients with a slipped horizontal rectus muscle [7, 8]. Recession of both horizontal rectus muscles in patients with Duane syndrome who have severe globe retraction in the primary position can significantly reduce globe retraction, resulting in widening of the palpebral fissures. Sprunger [9] reported a mean reduction in globe retraction of 3.0 mm (>Fig. 26.4). Full tendon transposition of the superior rectus and inferior rectus muscles to the lateral rectus muscle insertion can be associated with globe retraction and lid fissure narrowing during adduction of the involved eye, due to restrictive forces in adduction that are created by the transposition procedure. In our experience, this is more likely to occur if the transposition procedure has been enhanced using the posterior fixation suture

Chapter 26

technique described by Foster [10] (>Fig. 26.5). The problem is usually mild and is rarely bothersome to patients. Resection of the lateral rectus muscle in patients with Duane syndrome may worsen the co-contraction and lid fissure narrowing on adduction. Lateral rectus resection is rarely indicated in Duane syndrome and should almost never be done, especially when significant co-contraction already exists. Lagréze and coworkers [11] reported that eyelid fissure width changes occurred commonly following isolated horizontal rectus muscle surgery (>Fig. 26.6). The majority of the effect occurs due to changes in lower eyelid position, while upper eyelid position showed a variable response to horizontal rectus muscle surgery. A mean change in the width of the palpebral fissures of 1 mm was typical of a recession or resection procedure on a single horizontal rectus muscle of 7.7 mm. They believed that the change in eyelid fissure width was induced by changes in muscle tension that resulted in displacement of the eye in the anterior–posterior axis, with subsequent alteration of lid position. They suggested that surgical planning might be utilized to compensate for preexisting lid fissure differences.

Fig. 26.4. Improvement of lid fissure narrowing in Duane syndrome following recession of both horizontal rectus muscles in the involved eye right eye. Before (above) and after (below) surgery. (Courtesy of Derek T. Sprunger, MD)

Fig. 26.5. Globe retraction and lid fissure narrowing present on adduction of the right eye in a patient who has undergone transposition surgery with posterior fixation suture augmentation to treat a sixth nerve palsy in the right eye

 

Fig. 26.6. Lid fissure changes following standard horizontal rectus muscle surgery. {Reprinted from Lagréze WA, Gerling J, Staubach F (2005) Changes of the lid fissure after surgery on horizontal extraocu-

26.4 Ptosis and Pseudoptosis Though mild ptosis may occur following resection or advancement of the superior rectus muscle, pronounced ptosis is uncommon. Injury to the levator aponeurosis can occur as a result of intraoperative eyelid retraction with an eyelid speculum. This complication is uncommon and is most likely to occur in elderly patients who presumably have tenuous connections between the levator aponeurosis and the tarsal plate. Marked postoperative edema or hemorrhage into the upper eyelid can also result in injury to the levator aponeurosis, producing ptosis. Temporary ptosis is often seen in the immediate postoperative period (>Fig. 26.7). It can be the result of eyelid edema and can occur as a side-effect of local ocular corticosteroid administration. The cause of ptosis associated with topical corticosteroid administration is believed to be related to a myopathic effect of the agent on Mueller’s muscle [12] although others have suggested that it is caused by a myopathic effect of the vehicle rather then the corticosteroid itself [12]. Patients with severe restrictive strabismus due to congenital or acquired fibrosis and contracture of the inferior rectus muscle(s) often present with simultaneous hypotropia of the involved eye and apparent ptosis. Pseudoptosis may occur in this setting because of the natural tendency for the upper eyelid to move downward during infraduction, as the superior rectus muscle relaxes. It is not always possible for the surgeon to determine if true ptosis or pseudoptosis is present in this setting, especially when planning surgery on a young child. Correction of the strabismus alone by recession of the restricted inferior rectus muscle may result in complete restoration of the upper eyelid to its normal position, confirming a diagnosis of pseudoptosis. Thus, simultaneous surgery on the upper eyelid in this setting is contraindicated and can result in marked upper eyelid retraction. The child in Fig. 26.8 had bilateral congenital fibrosis of the inferior rectus muscles, an inability to elevate

26.4  Ptosis and Pseudoptosis

lar muscles. Am J Ophthalmol 140:1145–1146, copyright 2005, with permission from Elsevier [11]}

the eyes to midline, marked ptosis, and a pronounced chin-up head posture. In this case, recession of the inferior rectus muscles resulted in moving the eyes to the primary position but the ptosis persisted and ptosis surgery was required. Pseudoptosis is also common in patients with monocular elevator deficiency (also known as double elevator palsy).

Fig. 26.7. Mild, temporary ptosis noted 1 week after strabismus surgery

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Chapter 26 Fig. 26.8. Child with congenital fibrosis of the inferior rectus muscles with ptosis of the upper eyelids that persisted after recession of restricted inferior rectus muscles, confirming a diagnosis of true not pseudoptosis

26.5 Lid Changes Associated with Inferior Oblique Muscle Anterior Transposition Anterior transposition of the inferior oblique muscles is most commonly performed on both eyes, but occasionally is performed unilaterally. Regardless if performed on one or both eyes, alteration of the eyelids can occur and may be a source of concern for patients after surgery. During this procedure, the inferior oblique muscle is detached from the sclera and is reattached to the sclera near the temporal border of the inferior rectus muscle insertion. Because of attachments between the inferior oblique muscle and the lower eyelid retractors, the contour of the lower eyelid can be and often is altered following surgery. In a prospective study of patients undergoing inferior oblique anterior transposition, Kushsner [4] noted a number of changes that could occur in the contour of the lower eyelid following inferior oblique muscle anterior transposition surgery. He reported that the lower eyelid tends to become elevated in the primary position relative to the unoperated state (>Fig. 26.9). The lower eyelid also tends to rise or elevate with up gaze and a bulge may be noted in the lower eyelid in the area of the transposition (>Fig. 26.10). There is narrowing of the palpebral fissure, which may be particularly noticeable in patients with asymmetric or unilateral inferior oblique anterior transposition. He concluded that anterior transposition of the inferior oblique muscle commonly produced a noticeable effect on the size of the palpebral fissure and on the lower eyelid

Fig. 26.9. Elevation of the right lower eyelid and loss of the normal inferior curvature of the lid margin following unilateral inferior oblique anterior transposition

configuration in up gaze. In addition to narrowing of the palpebral fissure, Kushner [4] also reported marked upper eyelid retraction in three patients with a previous history of superior rectus muscle recession following anterior transposition of the inferior oblique muscles.

26.6 Eyelid Adhesions Fascial attachments between the vertical rectus muscles and the eyelid retractors are generally severed in the normal course of surgery on the vertical rectus muscles. Excessive dissection of the fascial planes between the superior rectus muscle and the levator muscle can lead to the development of adhesions between the superior rectus muscle and the levator palpebrae superioris muscle. We cared for a patient with this complication following retina surgery who exhibited a hypertropia upon elevation of his eyelids due to adhesions between the superior rectus muscle and the levator muscle of the upper eyelid. Several attempts to surgically correct the problem failed. Simpson and co-workers [13] reported a patient with thyroid-related ophthalmopathy who underwent simultaneous recessions of the levator palpebrae superioris and lateral rectus muscles in both eyes. Postoperatively, the palpebral and bulbar conjunctiva of the right eye fused. This produced postoperative ptosis and restriction of ocular motility. Movement of the right globe produced abnormal lid movements and movement

Fig. 26.10. A visible bulge noted in the lower eyelid with up gaze in a patient with a history of inferior oblique anterior transposition surgery in right eye

 

of the lids produced abnormal movement of the right globe. The adhesions were easily severed and anomalous movements improved. The authors recommended performing eyelid surgery and strabismus surgery in sequential operations rather than simultaneously to avoid this complication.

26.7 Preseptal Cellulitis Preseptal cellulitis is discussed in detail in Chap. 22. Postoperative cellulitis has been estimated to occur at a frequency of 1 in 1100 strabismus operations [14]. We have learned that when a parent or patient calls with a concern about redness in the immediate postoperative period to ask them specifically about redness and swelling of the eyelids. Significant redness and swelling of the eyelids is very unusual following uncomplicated strabismus surgery and is often (if not usually) a sign of postoperative preseptal cellulitis (>Fig. 26.11). Systemic antibiotics are warranted. Though some reports have recommended hospitalization with intravenous antibiotic administration for treatment of postoperative cellulitis [14], most patients we have treated with preseptal cellulitis and no signs of orbital involvement after strabismus surgery were effectively managed in an outpatient setting with oral and/or intramuscular antibiotics. Patients with advanced ocular signs or symptoms, and/or constitutional signs including fever, reduced appetite, and/or lethargy, and patients who fail to improve after 24 h of outpatient therapy should be considered for admission and intravenous antibiotics. Careful anterior segment examination and indirect ophthalmoscopy are indicated following administration of dilating drops to rule out concurrent intraocular infection. We have not seen intraocular infection in association with preseptal cellulitis, but we believe that the risk of intraocular infection may be higher in this setting and this concern has been raised by Parks [15]. The choice of antibiotics depends upon the age of patient and the local microbial spectrum. In some areas of the country, methicillin-resistant Staphylococcus aureus represents the bulk of serious staphylococcal infections, including community-acquired infections, and clindamycin is often the drug of choice. Moxifloxacin is a reasonable consideration because of its ability to penetrate the blood–ocular barrier at therapeutic levels [16].

Fig. 26.11. Preseptal cellulitis of the right upper eyelid that developed 3 days after uncomplicated horizontal rectus muscle surgery

26.9  Burns

26.8 Eyelid Ecchymosis and Hematoma Eyelid bruising and hematoma formation following strabismus surgery is unusual. It occurs most commonly in our experience following surgery on the inferior oblique muscle and following prolonged, complex reoperations, especially involving mani­pulation in the posterior aspect of the orbit (>Fig. 26.12). Eyelid ecchymosis and hematoma formation is generally benign and self-limiting. Severe hemorrhage and hematoma formation in the upper eyelid can cause damage to the levator aponeurosis with resulting ptosis. We have seen prolonged discoloration of the eyelid related to a hematoma in one patient lasting several months and producing great distress in the child’s family. Hemorrhage after strabismus surgery, including eyelid hemorrhages, is discussed in detail in Chap. 24.

26.9 Burns Thermal burns to the ocular adnexa during eye surgery are rare, but have been reported. There are several potential sources of thermal injury in an operating room. Supplemental oxygen that gathers under the surgical drapes in high concentrations can lead to fires when cautery is used [17]. The use of compressed air rather than oxygen has been suggested as a method to reduce fire hazard during ophthalmologic procedures [18]. Inadvertent burns of the eyelids can also occur during attempted cautery of other ocular structures if the cautery device comes in contact with the skin. This is most likely to occur with use of thermal cautery, and is generally mild. Other, more unusual causes of burns are also possible. For example, we performed transillumination of the globe through the eyelids in a patient after surgery for reasons unrelated to her strabismus surgery. Our standard transilluminator was not available, prompting use of the fiber-optic attachment on the operating room headlamp. The surgeon first touched the end of the fiber-optic light source to confirm that it was not hot. Noting that it was completely cool, it was then placed on the skin of the lateral canthal area and used to transilluminate the globe. Upon completion of this procedure, small round burns were noted on the skin in the lateral canthal area. This prompted the

Fig. 26.12. Eyelid ecchymosis following surgery on the inferior oblique muscle

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surgeon to hold the tip of the fiber-optic light source against his own hand for several seconds, after which it became immediately apparent that prolonged contact with this otherwise cool light source results in the production of a great deal of heat. Our patient healed without sequelae, and an important lesson was learned.

References 1.

2.

3.

4.

5.

6.

Pacheco EM, Guyton DL, Repka MX (1992) Changes in eyelid position accompanying vertical rectus muscle surgery and prevention of lower lid retraction with adjustable surgery. J Pediatr Ophthalmol Strabismus 29:265–272 Meyer DR, Simon JW, Kansora M (1996) Primary infratarsal lower eyelid retractor lysis to prevent eyelid retraction after inferior rectus muscle recession. Am J Ophthalmol 122:331–339 Helveston EM (1986) Pediatric ophthalmology and strabismus. Transactions of the New Orleans Academy of Ophthalmology. Raven, New York, pp 61–70 Kushner BJ (2000) The effect of anterior transposition of the inferior oblique muscle on the palpebral fissure. Arch Ophthalmol 118:1542–1546 Jampolsky A (1986) Management of vertical strabismus. In: Transactions of the New Orleans Academy of Ophthalmology. New Orleans Academy of Ophthalmology. Raven, New York, pp 154–157 Patel MP, Shapiro MD, Spinelli HM (2005) Combined hard palate spacer graft, midface suspension, and lateral canthoplasty for lower eyelid retraction: a tripartite approach. Plast Reconstr Surg 115:2105–2114; discussion 2115–2117

Chapter 26 7.

8.

9.

10. 11.

12.

13.

14.

15. 16.

17. 18.

Ohba M, Ohtsuka K, Hosaka Y, Ogawa K, Osanai H (2004) A case of a slipped medial rectus muscle after strabismus surgery. Binocul Vis Strabismus Q 19:165–168 Bloom JN, Parks MM (1981) The etiology, treatment and prevention of the “slipped muscle”. J Pediatr Ophthalmol Strabismus 18:6–11 Sprunger DT (1997) Recession of both horizontal rectus muscles in Duane syndrome with globe retraction in primary position. J AAPOS 1:31–33 Foster RS (1997) Vertical muscle transposition augmented with lateral fixation. J AAPOS 1:20–30 Lagréze WA, Gerling J, Staubach F (2005) Changes of the lid fissure after surgery on horizontal extraocular muscles. Am J Ophthalmol 140:1145–1146 McGhee CN, Dean S, Danesh-Meyer H (2002) Locally administered ocular corticosteroids: benefits and risks. Drug Saf 25:33–55 Simpson WA, Downes RN, Collin JR (1989) Unusual complication of strabismus and lid surgery. Ophthalmol Plast Reconstr Surg 5:131–132 Kivlin JD, Wilson ME Jr. (1995) Periocular infection after strabismus surgery. The Periocular Infection Study Group. J Pediatr Ophthalmol Strabismus 32:42–49 Parks MM (1989) Routine antibiotic coverage in eye muscle surgery [letter]. Binocular Vision Q 4:152–153 Hariprasad SM, Shah GK, Mieler WF et al (2006) Vitreous and aqueous penetration of orally administered moxifloxacin in humans. Arch Ophthalmol 124:178–182 Ho SY, French P (2002) Minimizing fire risk during eye surgery. Clin Nurs Res 11:387–402 Neatrour GP, Lederman IR (1989) Reducing fire hazard during ophthalmic surgery by using compressed air. Ophthalmic Surg 20:430–432

Unexpected and Atypical Anatomy

Chapter

27

27 Most strabismus operations are straightforward and are performed without serious complications or surprises. Despite this, there are many situations the strabismus surgeon may encounter that are not so straightforward. Abnormal and/or unexpected anatomical issues may be anticipated prior to surgery or they may be unanticipated and first discovered intraoperatively. The purpose of this chapter is to review some of the more common scenarios that may be encountered before and during strabismus surgery that may alter management options.

27.1 Congenital Aplasia of the Extraocular Muscles Anomalous embryologic development of mesodermal tissues around the eye can result in agenesis of extraocular muscles. The inferior rectus, inferior oblique, and the inferior portion of the lateral rectus muscle are thought to originate from a common inferior mesodermal complex embryologically. The remaining extraocular muscles, including the levator palpebrae superioris, are thought to be derived from a superior mesodermal complex [1]. Congenital aplasia and hypoplasia of each of the extraocular muscles has been reported. Congenitally absent muscles have been reported most commonly in patients with craniofacial dysostosis syndromes and chromosomal abnormalities. However, the condition can occur in otherwise healthy individuals and is not always recognized preoperatively. Strabismus surgery on patients with absent or hypoplastic extraocular muscles can be complex. Nonstandard surgical techniques, such as transposition procedures and suspension procedures, are often required. This discussion will begin with a review of muscle abnormalities in patients with craniofacial syndromes and be followed by a review of management options for specific muscle abnormalities.

27.2 Craniofacial Dysostosis Syndromes Strabismus is common in patients with craniofacial syndromes. Strabismus in this patient subset is often atypical. Patients may have both horizontal and vertical deviations and commonly

have marked apparent overaction and/or underaction of the oblique muscles. Strabismus in this patient subset can occur due to a combination of one or more factors including muscle disturbance created by abnormal orbital anatomy, paralytic strabismus, and absent or hypoplastic extraocular muscles. In addition, orbital anatomy is often so abnormal that the rectus muscle paths are altered [2] and the trochlea of the superior oblique muscle may be abnormally located [3] (>Fig. 27.1). All six extraocular muscles have been reported as congenitally absent or hypoplastic in patients with craniofacial syndromes [4–6]. Coats and coworkers [5] reported a patient with congenital absence of 11 of the 12 extraocular muscles. They pointed out that ophthalmic surgeons only surgically manipulate the distal aspect of the extraocular muscles and that true absence of the entire muscle can only be determined through neuroimaging of the orbits. Because any of the extraocular muscles or multiple muscles may be congenitally absent or hypoplastic in patients with craniosynostosis, Greenberg and Pollard [6] recommend limited exploration of all of the extraocular muscles during surgery to repair strabismus in patients with craniosynostosis. Generally speaking, standard surgical techniques may be less effective in the treatment of strabismus associated with craniofacial syndromes. Coats and coworkers [5] reported lack of effectiveness of several operations that had been attempted to correct V-pattern strabismus with severe oblique dysfunction in patients with craniofacial syndromes. Among 14 patients who underwent 16 operations, including medial rectus muscle infraplacement, inferior oblique recession, inferior oblique myectomy, inferior oblique anterior transposition, and inferior oblique denervation/extirpation, all patients had significant residual ocular motility disturbances. Denervation and extirpation of the inferior oblique muscle and inferior oblique myectomy of the overacting inferior oblique muscles offered the best, but still suboptimal, improvement. Agenesis of the superior oblique tendon appeared to be the cause of severe inferior oblique overaction in a large proportion of affected patients. Stager and coworkers [7, 8] reported the use of nasal and anterior transposition of the inferior oblique muscle insertion to correct recurrent inferior oblique overaction, including that associated with agenesis of the superior oblique tendon ­(Chap. 11). The timing of strabismus surgery relative to craniofacial surgery depends upon the age of the child, condition, and the

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Chapter 27

Fig. 27.1. The trochlea of the superior oblique muscle is often posteriorly located in patients with coronal synostosis, altering the effect of superior oblique muscle contraction on movement of the globe, limiting its depression function

opinion and experience of the surgeon. On the one hand, craniofacial surgery can and often does alter ocular alignment; hence, some surgeons prefer to defer strabismus surgery until craniofacial surgery has been completed. On the other hand, it is more likely that a patient will attain binocularity if strabismus surgery is performed early; hence, some surgeons prefer to perform strabismus surgery as early as possible, even if this means performing surgery prior to completion of craniofacial surgery. The surgeon and patient should recognize that additional strabismus surgery may be required later if ocular alignment is altered by the future craniofacial surgery. A compromise approach might be to perform surgery early if the patient presents for ophthalmologic evaluation early in life. If the patient presents in later childhood or adulthood, deferring surgery until craniofacial surgery has been completed may be optimal, since the chance of obtaining binocularity is reduced in older age groups. Strabismus can negatively impact an already difficult situation for affected patients, and we have been willing to perform surgery prior to completion of craniofacial surgery even in late presenting patients when the patient desires earlier treatment. Experience has demonstrated that a formula or cookbook approach to the management of strabismus in patients with congenital absence of more than one extraocular muscles is not feasible. The surgeon is left with a decision on how to maximally transfer remaining functional extraocular muscles to improve the patient’s ocular motility status, taking care to ensure that adequate anterior segment circulation is main-

tained and the patient is not put at excessive risk for anterior segment ischemia. Greenberg and Pollard [6] pointed out that some evidence exists that collateral anterior segment blood flow is reduced in patients with absent rectus muscles. We and others [9] have seen intact anterior ciliary vessels traveling in Tenon’s fascia and on the sclera in the area of the missing rectus muscles with these vessels ultimately entering the sclera in an area near the position where the missing muscle would have inserted, suggesting the presence of some degree of anomalous anterior segment circulation even when an extraocular mus­ cle is congenitally absent. The true nature of anterior segment circulation in patients with absent or hypoplastic extraocular muscles is unclear.

27.3 Aplasia of the Superior Oblique Muscle and/or Tendon The anatomy and function of the superior oblique muscle and tendon is more complex compared to the remaining five extraocular muscles. The presentation of congenital absence of the superior oblique muscle is variable and it may be impossible to make this diagnosis on clinical grounds alone. Chan and Demer [10] reported on the features of patients with congenital absence of the superior oblique muscle, which they confirmed was absent with orbital imaging in six patients. They compared patients with congenital absence of the superior oblique mus-

 

27.4  Aplasia of the Inferior Oblique Muscle

Fig. 27.2. Algorithm for the surgical management of strabismus caused by absence of the superior oblique muscle and/or tendon. (Reprinted from American Journal of Ophthalmology, volume 118, Wallace DK, von Noorden GK, Clinical characteristics and surgical management of congenital absence of the superior oblique tendon, pp 63–69, copyright 1994, with permission from Elsevier [11])

cle to patients with clinical evidence of a superior oblique palsy but with demonstrable superior oblique muscles on orbital imaging studies. Amblyopia was not present in any of their patients with unilateral absence of the superior oblique muscle. The mean incomitance of the hypertropia on head tilt testing and during lateral gaze overlapped the values of patients who had demonstrable superior oblique muscles present. Only one of the patients had concurrent horizontal strabismus. In contrast, Wallace and von Noorden [11] reported horizontal strabismus in seven of nine patients with congenital absence of the superior oblique muscle and Helveston and coworkers [12] reported concurrent horizontal strabismus in five of six patients. Wallace and von Noorden [11] published an algorithm for the surgical management of strabismus caused by the absence of the superior oblique muscle and/or tendon. No single procedure is appropriate for all patients and the surgical decision is based upon several factors including size of the vertical deviation, degree of excyclotorsion, concurrent horizontal strabis-

mus, and the degree of comitance (>Fig. 27.2). In addition to the scheme proposed by Wallace and von Noorden, Stager and co-workers [8] reported anterior and nasal transposition of the inferior oblique muscle (Chap. 11) to successfully treat patients with congenital absence of the superior oblique mus­cle, after failure of inferior oblique recession alone to adequately normalize ocular versions.

27.4 Aplasia of the Inferior Oblique Muscle Aplasia of the inferior oblique muscle is uncommon. We have only seen aplasia of the inferior oblique muscle in association with absence of other extraocular muscles [5]. Reports on the surgical management of this condition are not available and the surgeon should devise an individualized surgical plan to logically correct the patient’s deviation, taking into account the possible presence of other extraocular muscle abnormalities.

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Chapter 27

Fig. 27.3. Clinical presentation of agenesis for the inferior rectus muscle {Reprinted from Journal of AAPOS, 7, Astle WF and coworkers, Congenital absence of the inferior rectus muscle – diagnosis and management, pp 339–344, copyright (2003), with permission from the American Association for Pediatric Ophthalmology and Strabismus [14]}

27.5 Aplasia of the Inferior Rectus Muscle Aplasia of the inferior rectus muscle can be unilateral or bilateral. Though generally sporadic, it can occur in association with craniofacial syndromes and can be familial, even in otherwise healthy individuals. Pimenides and coworkers [13] reported aplasia of the inferior rectus muscles in a mother and her two children who had no signs of craniofacial dysostosis. Astle and coworkers [14] reported three otherwise normal patients with bilateral congenital absence of the inferior rectus muscle (>Fig. 27.3). The patients presented with marked inability to depress the involved eye(s) in abduction, often with A-pattern esotropia and a chin-down head posture. A neuroimaging scan is helpful when the diagnosis is suspected and readily demonstrates absence of the inferior rectus muscle(s) (>Fig. 27.4). Strabismus produced by an absent inferior rectus muscle is similar to that produced by paralysis of the inferior rectus muscle. Von Noorden and Hansell [15] reviewed the clinical characteristics and differential diagnosis in inferior rectus muscle paralysis. Presenting signs and symptoms included a highly incomitant vertical deviation, worse in the position of action

Fig. 27.4. Agenesis of the inferior rectus muscle is obvious on magnetic resonance imaging scan {Reprinted from Journal of AAPOS, 7, Astle WF and coworkers, Congenital absence of the inferior rectus muscle – diagnosis and management, pp 339–344, Copyright (2003), with permission from the American Association for Pediatric Ophthalmology and Strabismus [14]}

 

of the inferior rectus muscle, diplopia, and a head posture that consisted of a face turn with or without a head tilt. The head tilt was toward the paretic or paralyzed side in most, but not all, patients. They corrected the deviation with several procedures, which included inferior rectus resection and superior rectus recession in various combinations with other procedures and with contralateral superior oblique recession in one patient. While a recession/resection surgery may be effective for an inferior rectus muscle paresis, a transposition procedure involving partial or complete transfer of the medial and lateral rectus muscle insertion to the inferior aspect of the globe is usually required [16, 17]. The tendons of the medial and lateral rectus muscles are transposed to a position where the missing inferior rectus muscle would have inserted (>Fig. 27.5). The transposition procedure may be augmented using posterior fixation sutures (Chap. 13), if desired. Botulinum toxin can be administered to the antagonist superior rectus muscle for added surgical effect, though temporary ptosis is common postoperatively [14]. Gamio and coworkers [18] reported on the use of inferior oblique recession and anterior transposition to successfully treat three patients with absent inferior rectus muscles.

27.7  Aplasia of the Horizontal Rectus Muscle

Alignment of the eyes in the primary position can be achieved with transposition surgery. Two basic approaches can be considered. Mather and Saunders [9] successfully utilized a modified Jensen procedure in which the superior halves of the horizontal rectus muscle bellies were united using synthetic absorbable sutures without disinsertion of these muscles (>Fig. 27.6). Rattigan and Nischal [19] reported use of a transposition procedure of the medial and lateral rectus muscles superiorly with posterior fixation suture augmentation to treat three patients with craniofacial syndromes and a primary position hypotropia due to absence or severe thinning of the superior rectus muscle. They noted at the time of surgery that two of the patients had “massive subconjunctival fibrosis,” despite the fact that none of the patients had undergone previous strabismus surgery.

27.7 Aplasia of the Horizontal Rectus Muscle

Aplasia of the superior rectus muscle has been reported less frequently than aplasia of the inferior rectus muscle. Mather and Saunders [9] reported bilaterally absent superior rectus muscles in a child who appeared clinically to have a double elevator palsy. The child had abnormal eye movements consisting of paradoxical depression of the abducting eye on attempted elevation of the adducting eye. These authors suggested that absence of the superior rectus muscle should be considered when paradoxical eye movements are seen with attempted up gaze in patients exhibiting severe limitation of elevation.

Isolated aplasia of the horizontal rectus muscles has been reported infrequently. One or multiple [20] horizontal rectus muscles may be congenitally absent. The condition can occur in association with craniofacial syndromes and chromosomal abnormalities. Keith and coworkers [21] reported the absence of the right lateral rectus muscle and hypoplasia of the left lateral rectus muscle in a patient with duplication of the long arm of chromosome 7. Coats and coworkers [22] also reported hypoplasia of the lateral rectus muscles in a patient with partial duplication of the long arm of chromosome 7. A patient with isolated aplasia of a horizontal rectus mus­ cle presents with horizontal strabismus in the primary position and marked reduction or inability to move the eye in the direction of the absent muscle. When the primary position deviation is only moderate, a standard full tendon or partial tendon transposition procedure can be effective [23]. Posterior fixation suture augmentation or botulinum toxin injection

Fig. 27.5. The tendons of the medial and lateral rectus muscles are transposed to a position near to where the missing inferior rectus muscle would have inserted

Fig. 27.6. Modified Jensen-type transposition procedure, involving partial transposition of the horizontal rectus muscles without disinsertion to treat absence of the superior rectus muscle

27.6 Aplasia of the Superior Rectus Muscle

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to the antagonist muscle may be required to achieve optimal alignment. Standard, simultaneous recession of the antagonist muscle may be contraindicated because of the potential to compromise anterior segment circulation through simultaneous disruption of remaining anterior ciliary arteries in an eye with already disturbed anterior segment circulation. In longstanding cases, the primary position deviation can be large and severe limitation of ocular ductions may be present due to contracture of the antagonist. Standard strabismus surgery may not be adequate to achieve alignment in the primary position. We successfully treated a patient with hemifacial microsomia and congenital absence of the right lateral rectus muscle using a periosteal flap as a tether (Chap. 15) combined with extirpation of the anterior two-thirds of the patient’s contracted medial rectus muscle. The patient had an esotropia greater than 100 prism diopters preoperatively and could not abduct the involved eye beyond its fixed position in adduction.

27.8 Abnormal Muscle Paths and Heterotopic Rectus Muscle Pulleys Magnetic resonance imaging has been increasingly used to assess the extraocular muscle paths and rectus muscle pulley position in the evaluation of atypical strabismus. A large body of evidence has been published on the topic of heterotopic rectus muscle pulleys as the cause of many atypical and even some common strabismus patterns. Heterotopic rectus muscle pulleys have been reported to be the true cause of such varied conditions as some cases of Brown syndrome [24], incomitant strabismus [25], and apparent oblique muscle dysfunction [26]. While not practical or necessary for the routine management of strabismus, high resolution magnetic resonance imaging can be helpful in selected patients with unusual strabismus [27].

Chapter 27

inferior oblique muscle might alter the physiologic action of the muscle. Surgeons should be aware of the potential for the double-bellied inferior oblique muscles to be found at surgery and ensure that the entire muscle is disinserted at its origin or residual inferior oblique muscle action caused by the residual, undisturbed portion of the muscle may persist postoperatively, resulting in residual unwanted ocular misalignment. Postoperative traction testing, often suggested as the best way to ensure that the inferior oblique muscle has been completely disinserted, may not be sufficient to detect a small residual band of intact inferior oblique muscle [29] (>Fig. 27.7). We have been seen double-bellied inferior oblique muscles and multiple inferior oblique muscle insertions less frequently than reported by Deangelis and Kraft. However, in a cadaver study involving 200 eyes, Emmel and coworkers [30] found bifid or trifid inferior oblique muscle insertions in about 50% of cases. In the normal course of surgery to isolate the inferior oblique muscle, we believe that it is likely that the entire inferior oblique muscle is usually readily hooked and that the surgeon may not even recognize the presence of a double-bellied inferior oblique muscle since the entire muscle, including both bellies, is contained and compacted on a hook.

27.9.2 Superior Oblique Muscle/Tendon Helveston and coworkers [31] have reported variation in the anatomy of the superior oblique tendon in patients with congenital superior oblique palsy (>Fig. 27.8). In addition to redundant and absent superior oblique tendons, the tendon may insert on the nasal side of the superior rectus muscle or into

27.9 Abnormal Extraocular Muscle Insertions Extraocular muscle insertions have been reported to be abnormally anteriorly or posteriorly located on the globe, to have multiple attachments to the globe, and to have other unusual variations. Abnormalities of extraocular muscle origins, on the other hand, have rarely been reported. The lack of reports of muscle origin abnormalities may reflect the fact that surgeons typically encounter only the distal aspect of the muscle surgically, rather than a true paucity of abnormalities involving the extraocular muscle origins.

27.9.1 Inferior Oblique Muscle Deangelis and Kraft [28] reported finding a double-bellied inferior oblique muscle insertion in 10.9% of operated inferior oblique muscles. They noted that fundus excyclotorsion was more common in eyes that had a double-bellied inferior oblique muscle, and postulated that the double-belly of the

Fig. 27.7. Inferior oblique traction testing may be inadequate to detect residual, uncut fibers of the inferior oblique muscle

 

27.10  Accessory Muscle

Fig. 27.8a–d. Anatomical variations in the superior oblique tendon as reported by Helveston and coworkers [31]. a lax tendon, b abnormal insertion into the sclera, c abnormal insertion into Tenon’s capsule, with no scleral insertion, and d absent tendon

Tenon’s capsule rather than into the sclera. These variations in the anatomy of the superior oblique tendon are important to recognize intraoperatively as they may have significant impact on surgical decisions.

27.9.3 Bifid Rectus Muscles Bifid rectus muscle insertions have been reported in patients with craniofacial syndromes [32] and in otherwise healthy patients [33]. Sundaram and coworkers [33] reported a bifid medial rectus muscle insertion associated with intermittent distance exotropia in an otherwise healthy patient. Minor, intuitive modifications of the surgical plan are required to manage the bifid rectus muscle insertions. Our approach has been to suture the bifid components of the insertion together and recess or resect the two insertions as a unit.

27.9.4 Abnormal Rectus Muscle Insertions Rosenbaum and Jampolsky [34] reported pseudoparalysis caused by an abnormal insertion of superior rectus muscle, which was inserted just above the insertion of the lateral rectus muscle. Okano and co-workers [35] reported on the treatment

of a patient with severe exotropia and a preoperative diagnosis of adduction paralysis who was found to have an anomalous posterior insertion of a hypoplastic medial rectus muscle 11.5 mm from the limbus. The patient was satisfactorily treated with a Hummelsheim transposition procedure, though it is unclear why the authors did not simply advance the medial rectus muscle. Wine and co-workers [36] operated on a 5-year-old boy with congenital left hemiparesis associated with schizencephaly and a large V-pattern exotropia, who was found to have lateral rectus muscles that were abnormally inferiorly positioned. Despite recession with supraplacement, the V-pattern exotropia persisted postoperatively, though there was also untreated overaction of the inferior oblique muscles, which may have contributed to the problem.

27.10 Accessory Muscle In vertebrates, the retractor bulbi muscle is derived from the same embryonal tissue as other extraocular muscles. Several authors have reported the persistence of muscles in humans that were thought to be a vestige of the retractor bulbi muscle. Accessory extraocular muscles are uncommon, but when present they can produce bizarre and atypical strabismus. Anomalous orbital structures can produce a variety of unusual strabismus patterns [37]. Muhlendyck [38] has suggested that

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persistence of the retractor bulbi muscle might be a cause of some cases that are clinically diagnosed as Duane syndrome. Kirkham [39] reported an accessory inferior oblique muscle. Three major types of anomalous structures have been described: (1) those arising from the extraocular muscles themselves and inserting in abnormal locations, (2) fibrous bands that are located beneath the rectus muscles, and (3) discrete anomalous muscles originating from the posterior orbit and inserted in abnormal locations on the globe [37]. Clinical findings that may suggest the presence of an anomalous orbital structure include globe retraction, large vertical strabismus, and an elevation deficit that is worse in abduction [37]. Neuroimaging studies can be useful in identifying abnormal accessory extraocular muscles in the orbit (>Fig. 27.9). Surgical treatment depends upon signs and symptoms as well as the nature of the particular abnormal orbital structure. Park and Ou [40] reported a patient diagnosed with a congenital third nerve palsy who was found to have an accessory lateral rectus muscle medial and parallel to the normal lateral rectus muscle that produced restriction to forced duction testing in adduction. Recession of the accessory muscle combined with a recess/resect operation of the normal medial and lateral rectus muscles resulted in resolution of the restrictive forces with a good surgical outcome. Surgical treatment of accessory extraocular muscles is not always required. Valmaggia and coworkers [41] reported finding a supernumerary intraconal muscle in the posterior aspect of the left globe of a child with marked elevation deficiency of the involved eye (>Fig. 27.10). The clinical and radiographic features of this child suggested the persistence of an atavistic structure, the retractor bulbi muscle. Treatment was not recommended because the patient

was asymptomatic. Restrictive bands are sometimes found under the inferior rectus muscle in patients with congenital fibrosis syndromes.

Fig. 27.9. Abnormal accessory muscle noted on neuroimaging of the orbit. {Reprinted from Valmaggia C, Zaunbauer W, Gottlob I (1996) Elevation deficit caused by accessory extraocular muscle. Am J Oph­ thalmol 121:444–445, copyright 1996, with permission from Elsevier [41]}

Fig. 27.10. Limited up gaze in a child with an accessory extraocular muscle. {Reprinted from Valmaggia C, Zaunbauer W, Gottlob I (1996) Elevation deficit caused by accessory extraocular muscle. Am J Oph­ thalmol 121:444–445, copyright 1996, with permission from Elsevier [41]}

27.11 Atypical Restrictive Strabismus 27.11.1 Thyroid-Related Ophthalmopathy Enlargement of extraocular muscles can occur from a variety of processes including neoplasm, infections, inflammation, infiltrative disorders, and obstruction of orbital venous outflow. Thyroid ophthalmopathy is the most common cause of enlarged extraocular muscles in the adult population.

27.11.1.1 Oblique Muscle Involvement Extraocular muscle fibrosis and contracture occur in a relatively predictable pattern in most patients with thyroid-related ophthalmopathy. Generally, only the rectus muscles are clinically involved. The order of most to least likely rectus muscle to be involved is the inferior, medial, superior, and lateral rectus muscle, respectively. Oblique muscle involvement is less commonly recognized, but may occur. Thacker and coworkers [42] reported four patients with thyroid-related ophthalmopathy who presented with incomitant vertical strabismus, A-pattern horizontal strabismus, over depression in adduction, and under elevation in adduction. Each of the patients also had significant incyclotorsion. Clear evidence of superior oblique enlargement was noted on orbital imaging of each patient. Intraoperative traction testing revealed relative tightness of the superior oblique muscle/tendon in all patients. The patients were treated with superior oblique tenotomy or superior oblique tendon silicone spacer procedures. A 6-0 Prolene tendon retrieval suture (aka chicken suture) was placed in the end of the transected tendon to allow for recovery and reversal of the tenotomy, if required postoperatively. Additional surgical procedures were performed on the rectus muscles with adjustable sutures as needed. The ocular motility disturbance was dramatically reduced in three of the four patients.

 

27.11  Atypical Restrictive Strabismus

Fig. 27.11. Preoperative photos of a patient with thyroid-related ophthalmopathy including involvement of the horizontal and vertical rectus muscles and the superior oblique muscles

Both vertical rectus muscle involvement and involvement of the superior oblique muscle can lead to development of vertical strabismus. In contrast to vertical strabismus caused by vertical rectus muscle restriction which is typically relatively comitant across the horizontal gaze fields, Thacker and coworkers [42] reported that the restriction due to involvement of the superior oblique muscle tended to be markedly incomitant across the horizontal gaze fields. Failure to recognize involvement of the superior oblique muscle and operating only on the vertical rectus muscles could exacerbate the horizontal and vertical incomitance, and could worsen the A-pattern as well as increase the incyclotorsion [42].

27.11.2 Superior Rectus Muscle Involvement While the superior rectus muscle is often involved in patients with thyroid-related ophthalmopathy, involvement of the inferior rectus muscles is usually more severe and the presence of a hypotropia with limited up gaze usually predominates the clinical presentation. Simultaneous involvement of the superior rectus muscles and superior oblique muscles can produce very unusual strabismus in patients with thyroid-related ophthalmopathy. We treated a patient with thyroid-related ophthalmopathy who had severe restrictive strabismus includ-

ing a large angle esotropia, moderate angle left hypotropia, and incyclotorsion of 10° in the right eye and 12° in the left eye (>Fig. 27.11). The patient had previously undergone a 10-mm right medial rectus muscle recession prior to our evaluation. Orbital imaging revealed enlargement of all four rectus muscles in each eye and enlargement of the superior oblique muscle in both eyes (>Fig. 27.12). Forced traction testing was not done in the office preoperatively, and preoperative planning was based on the assumption that the left hypotropia was primarily due to asymmetric contracture of the left inferior rectus muscle relative to the right inferior rectus muscle and the incyclotorsion was thought to be due to involvement of the superior oblique muscles. The preoperative surgical plan was to perform asymmetric recession of the inferior rectus muscles and the left medial rectus muscle with adjustable sutures combined with tenotomy of the superior oblique tendon in both eyes. At surgery, the overwhelming finding on forced duction testing was severe contracture of the superior rectus muscles, particularly the right superior rectus muscle. Thus, it became immediately obvious that the preoperative plan was incorrect and that the left hypotropia was present because the patient preferred to fixate with the right eye, which had a more severely restricted superior rectus muscle. The down gaze innervation required to overcome the severely contracted right superior rectus muscle resulted in the development of the left hypotropia due to Hering’s law of equal innervation.

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Fig. 27.12. Orbital CT scan of the patient in Fig. 27.11

When an ocular deviation is due to restriction of the fixing eye, the primary consideration at surgery should be to free the restrictive forces in the fixing eye to make fixation and alignment in the primary position possible. Surgical decisions are guided by forced traction testing before and/or during surgery. In this case, the superior rectus muscle was recessed in both eyes, with a larger recession performed on the right superior rectus muscle. Nasal transposition of both superior rectus muscles was performed to help offset the large incyclotorsion. Evaluation of the fundus intraoperatively with indirect ophthalmoscopy revealed significant residual incyclotorsion. The right superior oblique tendon was noted to be extremely tight and a tenotomy was performed to help address the residual incyclotorsion. The left superior oblique tendon was moderately tight, and was left intact. A left medial rectus muscle recession with an adjustable suture was performed to treat the esotropia. Following postoperative adjustment, the incyclotorsion and esotropia were eliminated. He was able to overcome a small residual vertical deviation and achieve single vision by adopting a 20º right face turn. Because the patient was satisfied, no further treatment was recommended. This case emphasizes the importance of preoperative and intraoperative traction testing as well as the potential value of intraoperative examination of the fundus with indirect ophthalmoscopy for objective improvement in cyclotorsion in unusual cases. A hypertropia and superior rectus muscle restriction in patients with thyroid-related ophthalmopathy can be so severe as to greatly impede or completely preclude the ability to surgically approach the muscle using standard techniques. Not only is the insertion of the superior rectus muscle further from the limbus compared to the other rectus muscles, but also the orbital rim and upper eyelid both limit surgical access to a severely restricted superior rectus muscle. Ing [43] reported the use of an upper lid splitting technique to allow better exposure of a severely contracted superior rectus muscle (> Fig. 27.13). While this may seem an extraordinary step for a strabismus surgeon to take in approaching an extraocular muscle, the risk

Fig. 27.13. Upper eyelid splitting procedure to allow surgical access to a severely restricted superior rectus muscle. {Reprinted from Ing E (2005) Vertical upper-lid split incision for access to a severely restricted superior rectus muscle in a patient with Graves ophthalmopathy. J AAPOS 9:394–395, copyright 2005, with permission from the AAPOS [43]}

of complications when operating on an extremely contracted superior rectus muscle when exposure is poor can be significant enough to justify such an approach.

27.11.2.1 Exotropia in Thyroid-Related Ophthalmopathy Exotropia is extremely uncommon in patients with thyroidrelated ophthalmopathy. It is uncommon for several reasons: (1) significant lateral rectus muscle contracture is infrequent, (2) medial rectus muscle contracture is very common, and (3) contracture of the vertical rectus muscles, which have adduction as a tertiary function, is common. Each of these factors makes development of an exotropia unusual, except in the rare setting in which the lateral rectus muscle is asymmetrically involved relative to its antagonist, the medial rectus muscle, a condition which should be easily detected on orbital imaging. The presence of an exotropia in a patient with thyroid-related ophthalmopathy should trigger consideration of concurrent myasthenia gravis [44], a condition known to occur in a small proportion of patients with thyroid-related ophthalmopathy [45].

 

27.12 Strabismus Following Scleral Buckling Surgery

27.12  Strabismus Following Scleral Buckling Surgery Table 27.1. Possible etiologies of strabismus following scleral buckling surgery for treatment of retinal detachment Scarring and adhesions

Strabismus following scleral buckling surgery for repair of retinal detachments is usually temporary [46]. Causes of temporary diplopia include periocular edema, muscle hemorrhage and edema, and reduced vision precluding fusion. Persistent diplopia may be seen in as many as 5%–25% of patients according to a review performed by Seaber and Buckley [47]. Strabismus occurring following scleral buckling surgery has generally been attributed to scarring [48]. However, the condition is probably heterogeneous (>Table 27.1). High-resolution magnetic resonance imaging has revealed multiple other potential mechanisms [7], including occult rectus muscle disinsertion, restrictive interference by the explant, interference by a myopic staphlyoma, and anterior migration and transaction of a rectus muscle by an encircling explant. Fat adherence [37] and anesthetic myotoxicity related to retrobulbar injection [49] have also been reported as a possible cause of restrictive strabismus following scleral buckling surgery. There have been numerous reports of unintentional rectus muscle detachment following scleral buckling procedures [50–52]. This can occur as a direct complication of surgery or can be caused by anterior migration of an encircling element that detaches the muscle postoperatively. The detached muscle may retract into the posterior orbit or reattach to the globe posterior to the buckle. The patient in Fig. 27.14 presented with a right hypertropia as a result of anterior migration of a silicone encircling element with detachment of the inferior rectus muscle in her nonamblyopic eye. She did well following retrieval and reattachment of the inferior rectus muscle, which had retracted into the posterior orbit. The muscle was identified because of its intact attachments to the lower eyelid retractors in the inferior oblique muscle. Though not necessary for this patient due to the obvious nature of the problem, highresolution orbital imaging can be helpful in clarifying the diagnosis and in helping to devise an appropriate surgical plan.

Fig. 27.14. Anterior migration of an encircling band placed to treat a retinal detachment has resulted in erosion of the inferior rectus ­muscle insertion

Rectus muscles disinsertion Restrictive interference by explant Limitation of movement by a myopic staphlyoma Anterior migration and transaction of a rectus muscle Anesthetic myotoxicity related to retrobulbar injection

Many patients with strabismus following scleral buckling surgery present with both a horizontal and a vertical deviation [53]. Torsional strabismus can also occur [52, 54]. In a series by Cooper and coworkers [54] excyclotorsion was seven times more likely to occur than intorsion. Excyclotorsion was most commonly caused by partial or total disinsertion of the superior oblique tendon and tightening of the inferior rectus mus­cle related to the underlying scleral buckle. Intorsion occurred due to scarring of the superior oblique tendon to the nasal border of the insertion of the superior rectus muscle. Surgery was successful in reducing torsion 4° or more in almost 60% of their patients. The surgical plan was devised on a case-by-case basis and included standard recess/resect surgery of the rectus muscles, Harada–Ito procedures, inferior oblique recessions, adjustable sutures, and dissection of the scar tissue. No formula is available to manage such complex patients. For patients who require treatment of strabismus following scleral buckling surgery, reasonable treatment options may include standard strabismus surgery, botulinum toxin injection, and/or prism therapy [53]. The success of treatment using botulinum toxin has been conflicting [55, 56]. The majority of patients can achieve single binocular vision in the primary position with treatment [57]. The prognosis for restoring binocular vision is lower in patients who have had a macula-off retinal detachment, poor visual acuity, image distortion, and/or a history of multiple procedures for retinal detachment [53]. Some surgeons have recommended removal of the scleral buckle and other explants as the first step in the management of strabismus associated with scleral buckling surgery [58]. We have rarely found removal of encircling buckles to be of value in the treatment of strabismus following retinal detachment repair, and rarely recommend this as a first step. Hydrogel implants (see below) and larger radial elements impeding ocular ductions, however, usually require removal. Consultation with a retina surgeon may be appropriate in these cases to determine the risk of recurrent retinal detachment if removal of these explants is to be considered. While strabismus surgery performed on the eye that has not undergone a scleral buckling procedure is technically easier and may be associated with a greater likelihood of restoring single vision [58], patients with a history of unilateral retinal detachment are often, if not usually, reticent about having strabismus surgery performed on their sound eye. Thus, in most cases, we perform strabismus surgery on the eye that has undergone previous scleral buckling surgery because of strong

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patient preference. If surgery is performed on the sound eye in a patient with a relatively small deviation and without significant restriction of ocular ductions in the contralateral eye, surgical planning and the technical aspects of surgery are relatively straightforward. Strabismus surgery on an eye that has undergone previous scleral buckling surgery, on the other hand, can be challeng­ing. In general, more surgery is often required than would initially be suspected for the size of a given deviation. Surgery can be unpredictable, and therefore adjustable sutures may be considered when feasible. We generally attempt to correct strabismus without removal of the scleral buckle. Two technical problems commonly arise during surgery on an eye that has an intact scleral buckle. The first involves isolation and dissection of the target rectus muscle. Generally, the muscle can only be hooked posterior to the scleral buckle, because the muscle anterior to this point is usually tightly adherent to the capsule surrounding the explant. Careful dissection of the anterior aspect of the muscle from the underlying encapsulated scleral buckle can

usually be accomplished and the muscle can then usually be disinserted from the globe at its anatomical insertion. A standard recession can then be performed. Reattachment of the recessed muscle posterior to the scleral buckle is usually straightforward and relatively simple, provided good exposure of the surgical site is possible. Occasionally, a recessed muscle needs to be placed on the sclera in the area underlying or near the scleral buckle. The muscle should not be placed under the buckle, because the buckle will produce a posterior fixation suture effect limiting ocular ductions and the buckle may erode through the newly recessed muscle postoperatively. We prefer to suture the recessed muscle directly to the sclera and will often remove a small segment of the scleral buckle posteriorly, leaving the anterior portion of the scleral buckle intact. The muscle can then be sutured directly to the sclera (>Fig. 27.15). Occasionally we have found it necessary to suture rectus muscles directly to the scleral buckle and its surrounding capsule. This technique has worked well, but we are always concerned about long-term stability of the muscle

Fig. 27.15a–c. Removal of the posterior portion of a scleral buckle to allow the rectus muscle to be sutured to the sclera under the buckle. a Buckle exposed after detachment of rectus muscle, b posterior seg-

ment of buckle removed and discarded, and c muscle sutured directly to the sclera in the area previously under the buckle

Fig. 27.16a-c. a If unable to dissect a rectus muscle away from the scleral buckle, b the muscle can be cut posterior to the buckle, and c recessed or resected as needed

 

insertion when the muscle has been sutured to the scleral buckle and its capsule, and we try to avoid this technique when possible. It is sometimes impossible to cleanly dissect the anterior portion of a rectus muscle away from the capsule surrounding the scleral buckle. When this occurs, the rectus muscle can be transected at its junction with the posterior edge of the scleral buckle. The now shortened rectus muscle can then be recessed or resected as desired (>Fig. 27.16). Adjustable sutures can be helpful since the effect of surgery may be unpredictable; although while they are useful, adjustable sutures are often so technically challenging in this setting that this limits their use. The treatment of restrictive strabismus is usually limited to recession surgery alone. This may not be the case in many patients with scleral buckle-related strabismus, where restrictive forces tend to be relatively mild and resection of a rectus muscle is often required to achieve the desired effect, particularly if the patient is unwilling to have surgery performed on the sound eye. Reattaching a resected rectus muscle to the sclera may require placement of sutures slightly anterior to the scleral buckle in order to facilitate reattachment of the muscle to the globe. Patients with scleral buckle-related strabismus should understand that the prognosis for successful treatment is often guarded, depending on the complexity of the problem. Successful surgery may allow the patient to achieve single vision in the primary position, but the field of single vision may be small in some patients.

27.13 Hydrogel Explants Treatment of strabismus caused by hydrogel explants deserves special consideration. These explants are no longer used in scleral buckling surgery. Patients who have received hydrogel explants in the past may present with strabismus, pain, a feeling of orbital fullness, and a subconjunctival mass [59]. Hydrogel explants can enlarge dramatically over time and onset of symptoms may not occur until years after buckling surgery. The strabismus produced is restrictive in nature and may be worse in the mornings when the hydrogel implant has become hydrated during the patient’s dependent sleep position. Surgical correction of associated strabismus requires removal of the hydrogel explant. Removal of these explants is technically challenging. The hydrogel material is very fragile and fragments when surgically manipulated. It usually must be removed in piecemeal fashion. In a study involving 17 eyes of 15 patients, Kearney and coworkers [59] reported relief of pain and discomfort with improvement of ocular motility in all patients following removal of their hydrogel explants. Extraocular muscle surgery was not required in any of their patients following removal of the explant. Hydrogel sponges can slowly erode through the sclera and therefore consultation with a retinal surgeon is important when considering removal of a hydrogel explant. In the series reported by Kearney and coworkers [59], three eyes suffered intraoperative eye wall perforation, one developed bacterial endophthalmitis postoperatively, and five eyes developed recurrent retinal detachments.

27.15  Strabismus Associated with Glaucoma Setons

Fig. 27.17. Computed tomography scan of the orbit in a patient presenting with a small left hypotropia and a small esotropia. The presence of subtle enophthalmos prompted a scan to be ordered, revealing an old medial wall blowout fracture with entrapment of the medial rectus muscle

27.14 Occult Orbital Fractures Unsuspected occult blowout fractures can produce complex strabismus. A history of prior trauma may not be reported or even recalled by the patient. The surgeon must maintain a high index of suspicion and should consider orbital imaging of patients with atypical strabismus [60]. Strabismus associated with occult posterior orbital wall fractures is usually associated with at least mild restriction of ocular motility and is often, if not usually, associated with enophthalmos, which can be subtle. The patient in Fig. 27.17 presented with an atypical and unexplained small, but symptomatic, vertical and horizontal deviation. Careful examination of the left eye revealed mild enophthalmos. Computed tomography scanning of the orbits revealed an occult medial wall fracture with entrapment of the medial rectus muscle posteriorly. Though he did not recall a history of ocular trauma during our initial evaluation, he recalled suffering a significant bruise to his left eye during a boxing match 20 years beforehand, after we informed him of the presence of the fracture. The patient was sent to an oculoplastics specialist for repair of the fracture. In this case the diplopia resolved and strabismus surgery was not required. In many cases, strabismus will persist following fracture repair, though the deviation is often significantly altered by fracture repair.

27.15 Strabismus Associated with Glaucoma Setons Strabismus has been reported as a result of mechanical restriction caused by a variety of glaucoma drainage devices [61–67]. Proposed mechanisms for glaucoma implant-related strabismus (>Table 27.2) include an increase in the length–tension curve of the muscle induced by the underlying bleb, a posterior

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Table 27.2. Proposed mechanisms for glaucoma implant-related strabismus Increase in the muscle length–tension curve induced by underlying bleb Posterior fixation effect Bulk associated with the implant and its capsule Orbital–implant disproportion

fixation effect due to scarring behind the implant, bulk associated with the implant and its capsule, and orbital–implant disproportion [63, 65, 66]. The Baerveldt 350-mm2 glaucoma implant may be particularly prone to inducing heterotropia and ocular motility restriction [62]. The condition is best managed by removal or repositioning of the orbital glaucoma drainage device or removal of a large associated cyst, if present. The patient in Fig. 27.18 presented with vertical and horizontal diplopia following placement of an Ahmed valve in the superonasal orbit [66]. The patient would not allow surgery on her sound eye and would not allow the drainage device to be removed or moved. We were able to effectively counteract her strabismus by performing a resection and transposition of the superior rectus muscle, resulting in realignment of her eyes in the primary position with restoration of single vision in the primary position. Unless the drainage device is to be removed, the strabismus surgeon should avoid the area of active filtration. If the sound eye cannot be operated, this may mean devising a specific approach that will stay clear of the region such as resecting the inferior rectus for the treatment of a hypertropia, a condition that would normally be corrected through recession of the superior rectus muscle. No formula is available for treatment of glaucoma seton-related strabismus and each case must be managed with a uniquely designed surgical plan.

27.16 High Myopia Related Strabismus Atypical strabismus has been reported in patients with high myopia. Demer and von Noorden [68] reported restriction of eye movements due to contact between the posterior aspect of an elongated globe and the posterior orbital walls. In other cases, the cause of atypical strabismus in patients with high myopia has historically been less clear. Adult patients with high axial myopia may develop a progressive restrictive esotropia and hypotropia. The condition has been referred to as the “heavy eye syndrome.” Though moderate success has been reported with standard strabismus surgery [69] the condition generally does not respond adequately to standard recession and recession techniques. Several theories have been advanced to explain the cause of this unusual ocular motility disturbance in patients with high axial myopia . Theories proposed include structural abnormalities of the extraocular muscles [70], sixth nerve palsy, and myopathic paralysis of the lateral rectus muscle by compression of the muscle against the orbital rim by the enlarged globe [71]. Krzizok coworkers [72] evaluated a large

Fig. 27.18. Strabismus caused by mechanical restriction related to an Ahmed valve in the superonasal orbit

group of patients with this condition using magnetic resonance imaging. They demonstrated that the lateral rectus muscle was downwardly displaced in the mid orbit by a median of 3.4 mm (>Fig 27.19). Furthermore, they demonstrated that normalization of the lateral rectus muscle with a silicone loop (“guide pulley”) or a nonabsorbable suture resulted in good alignment with improvement of abduction and elevation [73]. Tsuranu and coworkers [74] and Nishida and coworkers [75] also reported on restrictive strabismus in patients with high myopia, noting that there was more significant disruption of the orbit in many cases than isolated inferior displacement of the lateral rectus muscle. They demonstrated that the posterior aspect of the globe became subluxated superiorly and temporally resulting in deviation of the anterior aspect of the globe medially and inferiorly. The patient in Fig. 15.7b, c demonstrates these findings. In addition to normalization of the paths of the lateral rectus muscle, we have utilized partial transposition of the superior and lateral rectus muscle bellies toward the superotemporal aspect of the orbit, securing the adjacent muscle bellies together as far posteriorly as possible using nonabsorbable suture as described in Chap. 15. The muscles are not disinserted during this transposition procedure, which resembles a Jensen transposition.

27.17 Brown Syndrome Acquired Brown Syndrome is usually unilateral and is not common. It has been associated with a number of conditions

 

27.18  Congenital Extraocular Muscle Fibrosis

Fig. 27.20. Use of a scalpel to detach a tight rectus muscle. The scalpel is used to gently cut through the insertion while the hook protects the underlying sclera

27.18 Congenital Extraocular Muscle Fibrosis

Fig. 27.19. Magnetic resonance imaging of the orbit of a patient with high myopia with esotropia and hypotropia, demonstrating disturbance of the paths of each of the rectus muscles, and displacement of the posterior globe up and out. {Reprinted with permission from Krzizok TH, Kaufmann H, Traupe H (1997) New approach in strabismus surgery in high myopia. Br J Ophthalmol 81:625–630, copyright 2007 [73]}

including rheumatoid arthritis, pseudotumor, sinusitis or sinus surgery, orbital abscess, endophthalmitis, orbital trauma, and metastatic disease, or it may be idiopathic. Rao and coworkers [76] reported a case of acquired Brown syndrome due to Cys­ ticercus cellulosae, a parasitic cyst. If an inflammatory etiology is suspected, injection of steroids adjacent to the trochlea can be an effective treatment, often resulting in resolution of symptoms within a few days. Orbital imaging studies can be helpful in both identifying the etiology and developing a surgical plan in noninflammatory cases.

Congenital fibrosis of extraocular muscles most commonly involves the inferior rectus muscles and/or medial rectus muscles, in our experience. Patients with congenital fibrosis involving the inferior rectus muscles may present with a severe hypotropia, chin-up head posture, and true ptosis or pseudoptosis. We have noted anomalous contracture of the medial rectus muscles in attempted up gaze in patients with bilateral congenital fibrosis involving the inferior rectus muscles. Up gaze limitation combined with contraction of the medial rectus muscles on attempted up gaze superficially resembles Perinaud syndrome, and these patients have often undergone neuroimaging prior to evaluation by us because of this concern. The distinguishing ophthalmologic feature is absence of globe retraction with attempted up gaze as occurs in Perinaud syndrome. The diagnosis of congenital fibrosis syndrome is often suspected in the first months of life, but the diagnoses may be difficult to confirm until the child is older, due to examination difficulties in an uncooperative child. Surgical correction requires recession of the fibrotic muscle(s). Free tenotomy may be required in severe cases. Disinsertion of a severely restricted muscle from the sclera can be hazardous and can result in laceration of the sclera. The use of a sharp blade to gradually transect the muscle by slowly cutting down through the muscle to the underlying muscle hook can reduce the risk of injuring the sclera (>Fig. 27.20).

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Chapter 27

27.19 Miscellaneous Muscle Abnormalities Acquired strabismus has occasionally been reported due to focal metastasis of a malignancy [77] and can also result from local benign and malignant neoplasia (>Fig. 27.21). Careful history and ophthalmologic examination and a strong index of suspicion in patients with atypical strabismus are required to diagnose these unusual situations. Extraocular muscle involvement has been reported with idiopathic primary systemic amyloidosis [78, 79]. Sharma and coworkers [80] reported a patient with strabismus fixus and severe convergence due to amyloidosis causing paralysis of the lateral rectus muscles. Bilateral horizontal recession/resection surgery resulted in significant improvement. We managed a patient with no history of amyloidosis who had a long history of esotropia and mild abduction deficit in the left eye. Historically the esotropia had been of sudden onset and had been stable for many years. A recess/resect operation on the left eye was planned to treat a presumed residual microvascular sixth nerve palsy. At surgery, a white/yellow material was noted to be adherent at the lateral rectus muscle. Concerned that the material might represent a neoplastic or infectious process, strabismus surgery was not performed. Instead, a biopsy of the lesion was made and histopathologic studies demonstrated amyloidosis.

Fig. 27.21. Patient with pseudo-Brown syndrome due to a benign tumor involving the inferior rectus muscle

References 1. 2.

3.

4.

27.20 Abnormalities of the Sclera

5.

27.20.1 Thin Sclera

6.

Areas of scleral thinning or scleral ectasia can present significant challenges when attempting to reattach a muscle to the sclera. When thin sclera is encountered, sutures can be placed in adjacent thicker sclera using a hang-back approach (Chap. 9). Alternatively, techniques that do not require placement of sutures into the sclera can be helpful [81, 82]. We developed a technique that allows rectus muscle recession or resection without the need to place sutures in the sclera. Muscle insertion sutures are used in place of scleral sutures and the muscle sutures are then tied to the insertion sutures to perform both a recession and a resection. This technique is reviewed in Chap. 21. Tissue adhesives have also been suggested for reattachment of a muscle to the sclera, but are not yet practical enough for common use. Scleral plaques often develop as a focal translucency of the sclera in elderly individuals [83]. The lesions are most often located anterior to the tendon insertion of the horizontal rectus muscles. With age, the plaques can become significantly calcified and contain a large amount of calcium sulfate. Attempting to pass suture needles through this material can be extremely hazardous. Instead, sutures should be passed through adjacent healthy sclera, utilizing a hang-back approach to accomplish the desired surgical result. The final resting position of the muscle should not overlie a scleral plaque, as it is unclear if the muscle will adhere to the plaque sufficiently to secure the muscle to the sclera.

7.

8.

9.

10.

11.

12.

13.

14.

15.

Sevel D (1981) A reappraisal of the origin of human extraocular muscles. Ophthalmology 88:1330–1338 Paysse EA, Khokhar A, McCreery KM, Morris MC, Coats DK (2002) Up-slanting palpebral fissures and oblique astigmatism associated with A-pattern strabismus and overdepression in adduction in spina bifida. J AAPOS 6:354–359 Bagolini B, Campos EC, Chiesi C (1982) Plagiocephaly causing superior oblique deficiency and ocular torticollis. A new clinical entity. Arch Ophthalmol 100:1093–1096 Drummond GT, Keech RV (1989) Absent and anomalous superior oblique and superior rectus muscles. Can J Ophthalmol 24:275–279 Coats DK, Paysse EA, Stager DR (2000) Surgical management of V-pattern strabismus and oblique dysfunction in craniofacial dysostosis. J AAPOS 4:338–342 Greenberg MF, Pollard ZF (1998) Absence of multiple extraocular muscles in craniosynostosis. J AAPOS 2:307–309 Wu TE, Rosenbaum AL, Demer JL (2005) Severe strabismus after scleral buckling: multiple mechanisms revealed by high-resolution magnetic resonance imaging. Ophthalmology 112:327–336 Stager DR Jr., Beauchamp GR, Wright WW, Felius J, Stager D Sr. (2003) Anterior and nasal transposition of the inferior oblique muscles. J AAPOS 7:167–173 Mather TR, Saunders RA (1987) Congenital absence of the superior rectus muscle: a case report. J Pediatr Ophthalmol Strabismus 24:291–295 Chan TK, Demer JL (1999) Clinical features of congenital absence of the superior oblique muscle as demonstrated by orbital imaging. J AAPOS 3:143–150 Wallace DK, von Noorden GK (1994) Clinical characteristics and surgical management of congenital absence of the superior oblique tendon. Am J Ophthalmol 118:63–69 Helveston EM, Giangiacomo JG, Ellis FD (1981) Congenital absence of the superior oblique tendon. Trans Am Ophthalmol Soc 79:123–135 Pimenides D, Young S, Minty I, Spratt J, Tiffin PA (2005) Familial aplasia of the inferior rectus muscles. J Pediatr Ophthalmol Strabismus 42:222–227 Astle WF, Hill VE, Ells AL, Chi NT, Martinovic E (2003) Congenital absence of the inferior rectus muscle – diagnosis and management. J AAPOS 7:339–344 von Noorden GK, Hansell R (1991) Clinical characteristics and treatment of isolated inferior rectus paralysis. Ophthalmology 98:253–257

  16. Munoz M (1996) Congenital absence of the inferior rectus muscle. Am J Ophthalmol 121:327–329 17. Cooper EL, Greenspan JA (1971) Congenital absence of the inferior rectus muscle. Arch Ophthalmol 86:451–454 18. Gamio S, Tartara A, Zelter M (2002) Recession and anterior transposition of the inferior oblique muscle [RATIO] to treat three cases of absent inferior rectus muscle. Binocul Vis Strabismus Q 17:287–295 19. Rattigan S, Nischal KK (2003) Foster-type modification of the Knapp procedure for anomalous superior rectus muscles in syndromic craniosynostoses. J AAPOS 7:279–282 20. Wong GY, Jampolsky A (1974) Agenesis of three horizontal rectus muscles. Ann Ophthalmol 6:909–12, 914–915 21. Keith CG, Webb GC, Rogers JG (1988) Absence of a lateral rectus muscle associated with duplication of the chromosome segment 7q32–q34. J Med Genet 25:122–125 22. Coats DK, Paysse EA, Palmer CG, Plager DA (1998) Ophthalmic findings with partial trisomy (duplication) of the long arm of chromosome 7. Can J Ophthalmol 33:337–341 23. Sandall GS, Morrison JW Jr. (1979) Congenital absence of lateral rectus muscle. J Pediatr Ophthalmol Strabismus 16:35–39 24. Bhola R, Rosenbaum AL, Ortube MC, Demer JL (2005) Highresolution magnetic resonance imaging demonstrates varied anatomic abnormalities in Brown syndrome. J AAPOS 9:438–448 25. Oh SY, Clark RA, Velez F, Rosenbaum AL, Demer JL (2002) Incomitant strabismus associated with instability of rectus pulleys. Invest Ophthalmol Vis Sci 43:2169–2178 26. Clark RA, Miller JM, Rosenbaum AL, Demer JL (1998) Heterotopic muscle pulleys or oblique muscle dysfunction? J AAPOS 2:17–25 27. Demer JL, Clark RA, Kono R, Wright W, Velez F, Rosenbaum AL (2002) A 12-year, prospective study of extraocular muscle imaging in complex strabismus. J AAPOS 6:337–347 28. Deangelis DD, Kraft SP (2001) The double-bellied inferior oblique muscle: clinical correlates. J AAPOS 5:76–81 29. Coats DK, Paysse EA (1997) Intraoperative traction testing to detect incomplete inferior oblique myotomy/myectomy. J AAPOS 1:197–200 30. Emmel DK, Apt L, Foos R (1982) Strabismus. In: Reinecke RD (ed) Proceedings of the International Strabismology Association. Grune and Stratton, New York, pp 669–673 31. Helveston EM, Krach D, Plager DA, Ellis FD (1992) A new classification of superior oblique palsy based on congenital variations in the tendon. Ophthalmology 99:1609–1615 32. Coats DK, Ou R (2001) Anomalous medial rectus muscle insertion in a child with craniosynostosis. Binocul Vis Strabismus Q 16:119–120 33. Sundaram V, Chen SD, Colley S, Hundal K, Elston J (2005) Bifid medial rectus muscle insertion associated with intermittent distance exotropia. Arch Ophthalmol 123:1453 34. Rosenbaum AL, Jampolsky A (1975) Pseudoparalysis caused by anomalous insertion of superior rectus muscle. Arch Ophthalmol 93:535–537 35. Okano M, Matsuo T, Konishi H, Hasebe S, Tadokoro Y, Ohtsuki H (1990) Anomalous posterior insertion of medial rectus muscle simulating congenital oculomotor palsy. Jpn J Ophthalmol 34:275–279

References 36. Wine SB, Saad N, Vella ME (2000) Bilateral inferior insertion of lateral rectus muscles associated with schizencephaly. Clin Exp Ophthalmol 28:69–70 37. Lueder GT (2002) Anomalous orbital structures resulting in unusual strabismus. Surv Ophthalmol 47:27–35 38. Muhlendyck H, Markakis E, Helwig AT (1991) In: Kaufman LM (ed) Abnormal retraction syndrome due to persistent retractor bulbi. Transactions of the 19th Meeting of the European Strabismological Association, Crete, pp 169–173 39. Kirkham TH (1970) Accessory extraocular muscle. Br J Ophthalmol 54:276–277 40. Park CY, Oh SY (2003) Accessory lateral rectus muscle in a patient with congenital third-nerve palsy. Am J Ophthalmol 136:355–356 41. Valmaggia C, Zaunbauer W, Gottlob I (1996) Elevation deficit caused by accessory extraocular muscle. Am J Ophthalmol 121:444–445 42. Thacker NM, Velez FG, Demer JL, Rosenbaum AL (2005) Superior oblique muscle involvement in thyroid ophthalmopathy. J AAPOS 9:174–178 43. Ing E (2005) Vertical upper-lid split incision for access to a severely restricted superior rectus muscle in a patient with Graves ophthalmopathy. J AAPOS 9:394–395 44. Vargas ME, Warren FA, Kupersmith MJ (1993) Exotropia as a sign of myasthenia gravis in dysthyroid ophthalmopathy. Br J Ophthalmol 77:822–823 45. Bartley GB (1994) The epidemiologic characteristics and clinical course of ophthalmopathy associated with autoimmune thyroid disease in Olmsted County, Minnesota. Trans Am Ophthalmol Soc 92:477–588 46. Mets MB, Wendell ME, Gieser RG (1985) Ocular deviation after retinal detachment surgery. Am J Ophthalmol 99:667–672 47. Seaber JH, Buckley EG (1995) Strabismus after retinal detachment surgery: etiology, diagnosis, and treatment. Semin Ophthalmol 10:61–73 48. Farr AK, Guyton DL (2000) Strabismus after retinal detachment surgery. Curr Opin Ophthalmol 11:207–210 49. Salama H, Farr AK, Guyton DL (2000) Anesthetic myotoxicity as a cause of restrictive strabismus after scleral buckling surgery. Retina 20:478–482 50. Marrakchi S, Malek I, Allagui I et al (2002) Spontaneously detached extraocular rectus muscles following scleral buckling with soft silicone sponges. A report of two cases. Binocul Vis Strabismus Q 17:223–226 51. Hamlet YJ, Goldstein JH, Rosenbaum JD (1982) Dehiscence of lateral rectus muscle following intrascleral buckling procedure. Ann Ophthalmol 14:694–697 52. Wolff SM (1983) Strabismus after retinal detachment surgery. Trans Am Ophthalmol Soc 81:182–192 53. Maurino V, Kwan A, Khoo BK, Gair E, Lee JP (1998) Ocular motility disturbances after surgery for retinal detachment. J AAPOS 2:285–292 54. Cooper LL, Harrison S, Rosenbaum AL (1998) Ocular torsion as a complication of scleral buckle procedures for retinal detachments. J AAPOS 2:279–284 55. Petitto VB, Buckley EG (1991) Use of botulinum toxin in strabismus after retinal detachment surgery. Ophthalmology 98:509– 512; discussion 512–513

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Unexpected and Atypical Anatomy 56. Lee J, Page B, Lipton J (1991) Treatment of strabismus after retinal detachment surgery with botulinum neurotoxin A. Eye 5 (Pt 4):451–455 57. Munoz M, Rosenbaum AL (1987) Long-term strabismus complications following retinal detachment surgery. J Pediatr Ophthalmol Strabismus 24:309–314 58. Fison PN, Chignell AH (1987) Diplopia after retinal detachment surgery. Br J Ophthalmol 71:521–525 59. Kearney JJ, Lahey JM, Borirakchanyavat S et al (2004) Complications of hydrogel explants used in scleral buckling surgery. Am J Ophthalmol 137:96–100 60. Ortube MC, Rosenbaum AL, Goldberg RA, Demer JL (2004) Orbital imaging demonstrates occult blow out fracture in complex strabismus. J AAPOS 8:264–273 61. Christmann LM, Wilson ME (1992) Motility disturbances after Molteno implants. J Pediatr Ophthalmol Strabismus 29:44–48 62. Smith SL, Starita RJ, Fellman RL, Lynn JR (1993) Early clinical experience with the Baerveldt 350-mm2 glaucoma implant and associated extraocular muscle imbalance. Ophthalmology 100:914–918 63. Munoz M, Parrish RK 2nd (1993) Strabismus following implantation of Baerveldt drainage devices. Arch Ophthalmol 111:1096–1099 64. Cardakli UF, Perkins TW (1994) Recalcitrant diplopia after implantation of a Krupin valve with disc. Ophthalmic Surg 25:256–258 65. Frank JW, Perkins TW, Kushner BJ (1995) Ocular motility defects in patients with the Krupin valve implant. Ophthalmic Surg 26:228–232 66. Coats DK, Paysse EA, Orenga-Nania S (1999) Acquired PseudoBrown’s syndrome immediately following Ahmed valve glaucoma implant. Ophthalmic Surg Lasers 30:396–397 67. Dobler-Dixon AA, Cantor LB, Sondhi N, Ku WS, Hoop J (1999) Prospective evaluation of extraocular motility following doubleplate molteno implantation. Arch Ophthalmol 117:1155–1160 68. Demer JL, von Noorden GK (1989) High myopia as an unusual cause of restrictive motility disturbance. Surv Ophthalmol 33:281–284 69. Bagheri A, Adhami F, Repka MX (2001) Bilateral recession-resection surgery for convergent strabismus fixus associated with high myopia. Strabismus 9:225–230

Chapter 27 70. Hugonnier R, Magnard P (1969) [Oculomotor disequilibrium observed in cases of severe myopia.] Ann Ocul (Paris) 202:713–724 71. Bagolini B, Tamburrelli C, Dickmann A, Colosimo C (1990) Convergent strabismus fixus in high myopic patients. Doc Ophthalmol 74:309–320 72. Krzizok TH, Kaufmann K, Traupe H (1997) Elucidation of restrictive motility in high myopia by magnetic resonance imaging. Arch Ophthalmol 115:1019–1027 73. Krzizok TH, Kaufmann H, Traupe H (1997) New approach in strabismus surgery in high myopia. Br J Ophthalmol 81:625–630 74. Tsuranu Y, Tabuchi H, Ataka S, Shiraki K, Miki T, Mochizuki K (2000) The mechanism of development in progressive esotropia with high myopia. In: Faber D (ed) Transactions of the European Strabismological Association. Swets and Zeitlinger, Barcelona, pp 218–229 75. Aoki Y, Nishida Y, Hayashi O et al (2003) Magnetic resonance imaging measurements of extraocular muscle path shift and posterior eyeball prolapse from the muscle cone in acquired esotropia with high myopia. Am J Ophthalmol 136:482–489 76. Rao VA, Kawatra VK, Ratnakar C (1987) Unusual cause of acquired inflammatory Brown’s syndrome. Can J Ophthalmol 22:320–323 77. Slavin ML, Goodstein S (1987) Acquired Brown’s syndrome caused by focal metastasis to the superior oblique muscle. Am J Ophthalmol 103:598–599 78. Goebel HH, Friedman AH (1971) Extraocular muscle involvement in idiopathic primary amyloidosis. Am J Ophthalmol 71:1121–1127 79. Macoul KL, Winter FC (1968) External ophthalmoplegia secondary to systemic amyloidosis. Arch Ophthalmol 79:182–184 80. Sharma P, Gupta NK, Arora R, Prakash P (1991) Strabismus fixus convergens secondary to amyloidosis. J Pediatr Ophthalmol Strabismus 28:236–237 81. Coats DK, Paysse EA (1998) Rectus muscle recession and resection without scleral sutures. J AAPOS 2:230–233 82. von Noorden GK (1982) Muscle surgery without scleral sutures. Ophthalmic Surg 13:113–114 83. Cogan DG, Kuwabara T (1959) Focal senile translucency of the sclera. Arch Ophthalmol 62:604–610

Chapter

Anesthesia-Related Complications

28

28 Effective and safe anesthesia is obviously important to patient safety and surgical outcomes. Difficulties that arise related to anesthesia can produce anxiety on the part of the surgeon as well as other operating room staff. A straightforward surgical case can rapidly evolve into a very difficult and even dangerous situation in the rare event that an anesthetic complication arises.

28.1 General Anesthesia The majority of strabismus surgery operations are performed under general anesthesia. Fortunately, serious complications involving general anesthesia are uncommon. The incidence of serious complications can be reduced through appropriate risk management. The specific details of medical disorders that increase the risk of an adverse event in patients undergoing general anesthesia are beyond the scope of this chapter. However, it is important to have an understanding of the patient’s general medical health prior to surgery. Patients with significant health disorders should discuss their upcoming surgery with their primary medical physician. In addition, consultation with an anesthesiologist prior to surgery can be helpful for patients with complex underlying medical disorders. Strabismus surgery is virtually always performed as an elective procedure and few cases cannot be postponed until the medical condition of the patient has been optimized. A note from the primary care physician that a complex patient may undergo general anesthesia is useful, but alone is not sufficient. It is the responsibility of the anesthesiologist to make a determination about the safety of the proposed anesthetic procedure given the medical background supplied by the patient, laboratory studies, and reports from other physicians treating the patient, where appropriate, Mechanical concerns regarding endotracheal intubation include patients with difficult airways and patients with cervical neck disorders. Patients with a short, thick neck or cervical spondylosis may be difficult to intubate. While generally considered primarily an anesthesia issue, Arnold and coworkers [1] reported a surgical complication related to a cervical neck abnormality. Unknown to the surgeon, the patient’s head was not in contact with the operating table, and movement of the head during surgery resulted in perforation of the globe with a suture needle. If the potential for a difficult intubation is recog-

nized beforehand, preparation for fiber-optic intubation, use of laryngeal mask, or a decision to perform surgery under local anesthesia may be made as appropriate. Patients with Down syndrome may have atlantoaxial instability making intubation problematic and this condition can be unrecognized in some patients. The value of preoperative screening remains debatable among pediatricians, orthopedists, and anesthesiologists [2].

28.2 Malignant Hyperthermia Malignant hyperthermia is a potentially lethal disorder that occurs in genetically susceptible people. The general signs of malignant hyperthermia include tachycardia, increased body metabolism, muscle rigidity, and fever that may exceed 43° C (110 °F) (>Table 28.1). Sequelae of malignant hyperthermia can include cardiac arrest, brain damage, organ system failure, and death. The genetic predisposition for malignant hyperthermia occurs in 1:10,000 people and the clinical incidence is approximately 1:62,000–1:84,000 cases, which means that not every patient with a genetic predisposition for malignant hyperthermia will develop the condition [3, 4]. Multiple genetic defects have been associated with the condition. The susceptibility to develop malignant hyperthermia is inherited in an autosomal dominant fashion. This means that children and siblings of a patient who has been identified as a malignant-hyperthermia-susceptible individual have a 50% chance of inheriting a genetic defect predisposing them to malignant hyperthermia as well. Malignant hyperthermia occurs as the result of a biochemical chain reaction within the skeletal muscles of susceptible

Table 28.1. Signs of malignant hyperthermia Temperature elevation Tachycardia Trismus Tachypnea Metabolic acidosis Rise of end-expiratory CO2

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patients as a response to commonly used general anesthetic agents. It is due to a dysregulation of intracellular calcium within skeletal muscles. The dysregulation occurs when a susceptible individual is exposed to certain anesthetic agents. Anesthetic agents that are known to trigger malignant hyperthermia include volatile inhalational agents as well as succinylcholine. Many agents are safe and may be used in patients who are thought to be at risk for malignant hyperthermia. During a malignant hyperthermia crisis, cellular calcium levels increase. This in turn causes an increase in metabolic rate, heat production, and muscle rigidity. Early signs of malignant hyperthermia may include masseter muscle spasm, metabolic acidosis, sinus tachycardia, a rise of end-expiratory CO2 and flushing of the skin. Later, complex arrhythmias, hypoxemia, hypotension, electrolyte abnormalities, rhabdomyolysis, and hyperthermia develop. Treatment of a possible early malignant hyperthermia crisis includes immediate discontinuation of triggering anesthetic agent(s), administration of 100% oxygen, adjustment of ventilation according to blood gas analysis, and administration of insulin to treat hyperkalemia. Dantrolene (1 mg/kg) is given via rapid intravenous infusion up to a total of 10 mg until symptoms of malignant hyperthermia resolve. Anti-arrhythmia therapy is administered as needed. The core temperature of the patient can be lowered through a variety of measures including ice packs, cold water lavage, and cooled intravenous fluids as needed. Dantrolene may be administered after the crisis has passed to prevent recurrence of symptoms in the immediate postoperative period. The best method to prevent a malignant hyperthermia crisis is to detect those individuals who may be susceptible prior to surgery. Patients with a family history of malignant hyperthermia or a history of a previous anesthetic complication suggestive of malignant hyperthermia should have a consultation with an anesthesiologist prior to surgery. These patients can undergo surgery without the use of triggering anesthetics. Typically surgery on at-risk patients is performed as the first surgical case of the day before volatile anesthetics are used in the anesthesia circuit.

28.3 Postoperative Nausea and Vomiting One of the most common adverse effects of general anesthesia in patients undergoing strabismus surgery is postoperative nausea and vomiting. While postoperative nausea and vomiting is not an uncommon complaint following general anesthesia for any procedure, it is especially common following strabismus surgery. In fact, strabismus surgery is considered one of the known risk factors for development of postoperative nausea and vomiting following general anesthesia. The feeling of nausea is a conscious recognition of excitation of the area in the medulla that is associated with the vomiting center. The vomiting center receives afferent input from the chemoreceptor trigger zone, the vestibular apparatus, the cerebellum, and other higher cortical and brain stem centers. These structures contain dopaminergic, muscarinic, serotoninergic, histaminic, and opioid receptors. The mechanism of action of antiemetic drugs may be partially due to blockade

Chapter 28

of these receptors. Because the chemoreceptor trigger zone is not protected by the blood–brain barrier, it can be activated by chemical stimuli received through both the systemic circula­ tion and the cerebrospinal fluid. The incidence of postoperative nausea and vomiting varies according to individual susceptibility as well as certain risk factors. Risk factors include the type of surgery being performed, a previous history of postoperative nausea and vomiting, a history of motion sickness, and the duration of surgery and anesthesia. A history of previous postoperative nausea and vomiting can increase the risk of recurrence by two or three times. The increase in risk of postoperative nausea and vomiting with longer duration of surgery may be due to the greater accumulation of emetogenic anesthetic agents. One study calculated that the risk for nausea and vomiting increased by 59% for each 30-min increase in surgical duration [5, 6]. Intraoperative anesthetic agents may increase or decrease the incidence of postoperative nausea and vomiting. Nitrous oxide has been reported to produce a greater incidence of vomiting in some studies. Propofol has been shown to be associated with a lower incidence of nausea and vomiting when used for induction of anesthesia, but the same effect has not been shown when total intravenous anesthesia with propofol is used [7]. There are several important postoperative factors that may increase the incidence of nausea and vomiting. Pain may prolong gastric emptying time with a resultant increase in nausea and vomiting. In addition, opioids may be used to treat post­ operative pain and can increase the risk of nausea and vomiting by directly stimulating the chemoreceptor trigger zone, increasing vestibular sensitivity, and reducing motility of the digestive system. Various opioids will affect each individual differently. Therefore, opioid-induced nausea and vomiting may be either increased or decreased depending on the pharmacologic agent used in a given patient. Pain relief with a combination of systemic opioids, local anesthetics and nonsteroidal anti-inflammatory drugs may be helpful at both managing pain and reducing the incidence of postoperative nausea and vomiting. Hypovolemia in the postoperative period can lead to dehydration, dizziness, and orthostatic hypotension which may increase nausea and vomiting. Thus, once the patient becomes dehydrated, postoperative nausea and vomiting may be exacerbated and thus hydration during and after surgery is important in reducing its incidence and severity. Goodarzi and coworkers [8] demonstrated that superhydration may further decrease the incidence of postoperative nausea and vomiting in children undergoing strabismus surgery. Antiemetic drugs may be used to either prevent or treat postoperative nausea and vomiting. Several classes of drugs exist that are frequently used for these purposes (>Table 6.2). Droperidol inhibits dopaminergic receptors in the chemoreceptor trigger zone. It has a short-lived anti-nausea affect and its common side-effects include sedation and drowsiness. Metoclopramide is a dopamine antagonist that can be used to treat opioid-induced nausea and vomiting. It may help to reverse the gastric stasis that occurs with morphine use. Scopolamine is a muscarinic receptor antagonist. Application of a scopolamine patch prior to anesthesia may reduce postoperative nausea

 

and vomiting. Side-effects of scopolamine include sedation, dry mouth, and visual disturbances because of the effect this agent has on accommodation. Ondansetron, granisetron, tropisetron, and dolasetron are 5-HT3 receptor antagonists. These agents have been shown to be effective in the prevention and treatment of postoperative nausea and vomiting [9–11]. Glucocorticosteroids also have an antiemetic affect. Their mechanism of action in this regard is unclear. Dexamethasone has been shown to have antiemetic effects that are similar to conventional antiemetic agents. Its antiemetic effects are enhanced when it is used in combination with another antiemetic medication [12]. There are multiple studies showing the effectiveness of a large number of other pharmacologic agents in the prevention and treatment of postoperative nausea and vomiting. Given the large number of studies demonstrating the usefulness of each individual medication, it is not surprising to find that no single agent and no single approach has been shown to be the best pharmacologic agent for this purpose. Many anesthesiologists use a combination of agents, with different mechanisms of action, to increase the efficacy of drug therapy. The management of postoperative nausea and vomiting is important not only because of its effect on patient comfort and safety, but because of its cost value. Prolonged nausea and vomiting in the postoperative period may result in a delay of discharge from the ambulatory surgery setting, requires the utilization of additional staff and material resources and tends to reduce the overall efficiency of the operating room. The fact that many of the medications used to prevent or treat postoperative nausea and vomiting have become very expensive counterbalances these savings to some degree, and several of the agents used to prevent and treat postoperative nausea and vomiting may produce drowsiness, which may also delay discharge. Further study and justification of their use will continue to be an issue.

28.4 Unintended Intraoperative Awareness Unintended intraoperative awareness, also called anesthesia awareness, occurs when a patient who is under general anesthesia becomes aware of some or all events that are occurring during surgery and is able to recall those events after surgery. Because neuromuscular blocking agents are routinely used in many patients undergoing general anesthesia, the patient may be unable to communicate with the surgical team when anesthesia awareness is happening. The frequency of anesthesia awareness ranges between 0.1% and 0.2% [13]. Patients may experience auditory recollections, sensations of not being able to breath and/or pain [13]. Over half of affected patients later report experiencing mental distress following surgery, which may include post-traumatic stress syndrome [14]. The incidence of anesthesia awareness is greater in patients to whom administration of the general anesthetic agent is minimized. This may occur when lower doses of general anesthetic are given to reduce potential side-effects, when anesthesia is delivered intravenously or if premature emergence from anesthesia occurs at the end of the procedure.

28.6  Retrobulbar and Peribulbar Injection

Although the patient undergoing general anesthesia is extensively monitored, recognition of anesthesia awareness is difficult. Typical indicators of physiologic and motor response, such as an increase in blood pressure, heart rate, and body movement, may be masked by the use of pharmacologic agents. Methods are being developed that measure brain activity ­ rather than physiological responses and may provide a method to prevent and/or detect anesthesia awareness. These methods are thus far less applicable to pediatric anesthesia than to adult anesthesia. In order to reduce the risk of anesthesia awareness, certain measures have been recommended. These include premedication with amnesic drugs, administration of more than a “sleep dose” of induction agents if they are to be followed immediately by endotracheal intubation, and avoidance of muscle paralysis unless absolutely necessary [15].

28.5 Local Anesthesia In an effort to reduce the risk of systemic complications, improve postoperative patient comfort, and reduce the postoperative nausea and vomiting associated with general anesthesia, many strabismus surgeons will perform surgery under local anesthesia when possible. Although many of the potentially more serious complications may be avoided with local anesthesia, this approach is not risk free and some risks not present with general anesthesia are introduced. The most common complication of local anesthesia is inadequate anesthesia. An inadequate sensory or motor block may make even the most routine procedure significantly more complicated. The region that is being blocked often dictates the effect obtained. For example, a retrobulbar injection of an anesthetic agent may not effectively block the eyelids. The frontal nerve, which carries sensation from the upper lid, passes through the superior orbital fissure and not through the intraconal space. Supplementation of the initial block through a follow-up injection or through use of a different injection technique may be required in some cases to obtain anesthesia sufficient to safely and comfortably carry out surgery.

28.6 Retrobulbar and Peribulbar Injection Atkinson provided the classic description of retrobulbar anesthesia for ophthalmic surgery in 1956 [16]. He used a 23-gauge needle which was inserted at the inferior/temporal margin of the orbit. He had the patient look up and away from the injection site. The needle was advanced posteriorly and above the orbital floor until it passed the globe and then it was directed toward the apex. Unsold and coworkers performed a study using computed tomography scans of a cadaver orbit [17]. They investigated the anatomy of the globe and optic nerve when the injection was given as described by Atkinson as well as when the patient was asked to look down and out during the injection. They suggested that having the patient look up and in placed the optic nerve in the direct path of the needle and also

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stretched the optic nerve potentially making it easier to penetrate with the needle and/or to enter the subarachnoid space. Based upon their findings, they suggested that the eye be maintained in the primary position during retrobulbar injection. Peribulbar anesthesia was first described in 1986 by Davis and Mandel [18]. Their original technique was designed not to enter the muscle cone with the needle tip. Given the fact that they used a 31-mm needle, it is likely that they did enter the muscle cone during at least some of their injections. The use of shorter needles with more recent techniques may have helped lower the risk of entering the muscle cone during peribulbar injection along with its associated increased risk of globe and optic nerve damage [19]. Potential complications of both retrobulbar and peribulbar anesthesia are similar. These include globe perforation and injection into the central nervous system via the subarachnoid space surrounding the optic nerve. There has been considerable variability in the documented incidence of globe perforation using either of these injection techniques. In addition, some cases of perforation of the globe probably go unnoticed. In theory, peribulbar anesthesia should be associated with a lower incidence of complications if the muscle cone is not entered during injection. The risk of perforation is higher if the globe is more than 26 mm in length [20]. If the needle is placed into the optic nerve it may cause direct injury to the nerve itself or may allow the anesthetic agent to spread into the central nervous system. Signs of central nervous system spread of anesthetic agent include shivering, drowsiness, apnea, respiratory depression, seizure activity, cardiac arrest, and contralateral decreased vision. It is for this reason, among others, that patients undergoing strabismus surgery utilizing retrobulbar or peribulbar anesthesia should have personnel trained in airway support and cardiopulmonary resuscitation available. Retrobulbar hemorrhage may also occur during the injection (Chap. 24). In most cases, surgery should be postponed until a later date if a significant retrobulbar hemorrhage occurs. The literature contains many case reports and case series about trauma to the extraocular muscles resulting from retrobulbar and peribulbar injections for cataract surgery. Many of these cases have led to the development of iatrogenic strabismus. Inferior rectus muscle trauma with a resultant restrictive strabismus and large postoperative hypotropia has been well described [21]. Any of the extraocular muscles can be damaged during retrobulbar injection. Care should be taken to avoid injecting in the region of any of the rectus muscles to avoid this complication, though it is probably not completely preventable even with the most meticulous technique.

28.7 Sub-Tenon’s Anesthesia In an effort to further reduce the risk of globe perforation with a sharp needle, local anesthesia can be delivered directly into the sub-Tenon’s space using a blunt-tipped cannula. It has been recommended that a small, flexible cannula be utilized to allow for deeper placement of the anesthetic agent into the space. It has also been suggested that a tight seal is essential to make certain that the anesthetic agent remains in the sub-

Chapter 28

Tenon’s space and does not leak out through the incision site. We have not found this to be an absolute requirement. In fact, we have not found it necessary to use a cannula specifically designed for sub-Tenon’s infusion and we have used sub-Tenon’s anesthesia in cases where a limbal incision has first been made under topical anesthesia and has proven sufficient for surgery. The fluid introduced into the sub-Tenon’s space will often cause some localized swelling of the tissues being operated. The operating surgeon should anticipate this because this tissue distortion can make surgical landmarks more difficult to visualize. We have not found this to be a significant drawback of this anesthetic technique. While the risks of many of the complications seen with retrobulbar and peribulbar injection are reduced with sub-Tenon’s anesthesia infusion, retrobulbar hemorrhage has been reported [22, 23] (Chap. 24). We treated a patient who experienced a retrobulbar hemorrhage during sub-Tenon’s infusion of anesthetic. The vortex vein in the region of the injection was clearly identified and was not the cause of this intraoperative hemorrhage causing us to theorize that the hemorrhage occurred secondary to a ruptured short ciliary vessel following distention of the orbital contents during anesthetic infusion [22].

28.8 Topical Anesthesia Topical anesthesia has become popular for adult cataract surgery. It provides excellent surface anesthesia. However, true topical anesthesia provides little to no anesthesia to the deeper tissues and produces no akinesia. Infusion of the topical anesthetic into the sub-Tenon’s space may provide some degree of deeper anesthesia and some degree of akinesia. The greatest potential risk associated with the use of topical anesthesia for strabismus surgery is loss of control of the operative situation. If the patient feels pain and/or moves, the possibility of scleral perforation and other complications is increased. The strabismus surgeon who is well versed in the use of topical anesthesia will recognize this potential limitation and prepare both himself/herself and the patient for the steps of surgery where movement by the patient may be particularly problematic. Each form of anesthesia has its own potential risks and benefits. Knowing the limitations and potential complications of each form of anesthesia will allow the strabismus surgeon to choose the most appropriate form of anesthesia for his/her patient.

References 1.

2.

Arnold R, Barnett M, Limstrom SA, Swanson D (2001) Vision loss associated with a stiff neck complicating strabismus surgery. Binocul Vis Strabismus Q 16:181–186 Litman RS, Zerngast BA, Perkins FM (1995) Preoperative evaluation of the cervical spine in children with trisomy-21: results of a questionnaire study. Paediatr Anaesth 5:355–361

  3.

Urwyler A, Hartung E (1994) [Malignant hyperthermia.] Anaesthetist 43:557–569 4. Halliday NJ (2003) Malignant hyperthermia. J Craniofac Surg 14:800–802 5. Apfel CC, Laara E, Koivuranta M, Greim CA, Roewer N (1999) A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers. Anesthesiology 91:693–700 6. Sinclair DR, Chung F, Mezei G (1999) Can postoperative nausea and vomiting be predicted? Anesthesiology 91:109–118 7. Tramer M, Moore A, McQuay H (1997) Meta-analytic comparison of prophylactic antiemetic efficacy for postoperative nausea and vomiting: propofol anaesthesia vs omitting nitrous oxide vs total i.v. anaesthesia with propofol. Br J Anaesth 78:256–259 8. Goodarzi M, Matar MM, Shafa M, Townsend JE, Gonzalez I (2006) A prospective randomized blinded study of the effect of intravenous fluid therapy on postoperative nausea and vomiting in children undergoing strabismus surgery. Paediatr Anaesth 16:49–53 9. Sadhasivam S, Shende D, Madan R (2000) Prophylactic ondansetron in prevention of postoperative nausea and vomiting following pediatric strabismus surgery: a dose-response study. Anesthesiology 92:1035–1042 10. Fujii Y, Tanaka H, Ito M (2002) Treatment of vomiting after paediatric strabismus surgery with granisetron, droperidol, and metoclopramide. Ophthalmologica 216:359–362 11. Wagner D, Pandit U, Voepel-Lewis T, Weber M (2003) Dolasetron for the prevention of postoperative vomiting in children undergoing strabismus surgery. Paediatr Anaesth 13:522–526 12. Splinter WM (2001) Prevention of vomiting after strabismus surgery in children: dexamethasone alone versus dexamethasone plus low-dose ondansetron. Paediatr Anaesth 11:591–595

References 13. Sebel PS, Bowdle TA, Ghoneim MM et al (2004) The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg 99:833–839, table of contents 14. Osterman JE, Hopper J, Heran WJ, Keane TM, van der Kolk BA (2001) Awareness under anesthesia and the development of posttraumatic stress disorder. Gen Hosp Psychiatry 23:198–204 15. Ghoneim MM (2000) Awareness during anesthesia. Anesthesiology 92:597–602 16. Atkinson WS (1956) Observations on anesthesia for ocular surgery. Trans Am Acad Ophthalmol Otolaryngol 60:376–380 17. Unsold R, Stanley JA, DeGroot J (1981) The CT-topography of retrobulbar anesthesia. Anatomic-clinical correlation of complications and suggestion of a modified technique. Albrecht Von Graefes Arch Klin Exp Ophthalmol 217:125–136 18. Davis DB 2nd, Mandel MR (1986) Posterior peribulbar anesthesia: an alternative to retrobulbar anesthesia. J Cataract Refract Surg 12:182–184 19. Davis DB 2nd, Mandel MR (1994) Efficacy and complication rate of 16,224 consecutive peribulbar blocks. A prospective multicenter study. J Cataract Refract Surg 20:327–337 20. Duker JS, Belmont JB, Benson WE et al (1991) Inadvertent globe perforation during retrobulbar and peribulbar anesthesia. Patient characteristics, surgical management, and visual outcome. Ophthalmology 98:519–526 21. Capo H, Guyton DL (1996) Ipsilateral hypertropia after cataract surgery. Ophthalmology 103:721–730 22. Olitsky SE, Juneja RG (1997) Orbital hemorrhage after the administration of sub-Tenon’s infusion anesthesia. Ophthalmic Surg Lasers 28:145–146 23. Rahman I, Ataullah S (2004) Retrobulbar hemorrhage after subTenon’s anesthesia. J Cataract Refract Surg 30:2636–2637

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Chapter

29

29 The evaluation and management of strabismus, including strabismus surgery, is not an exact science. Under- and overcorrection, other unanticipated postoperative alignment difficulties, and recurrence following strabismus surgery are not uncommon. There is as much art in the practice of strabismus surgery as there is science, perhaps more. In many cases, the surgeon may elect to intentionally undercorrect or overcorrect a deviation, anticipating slow postoperative drift of the patient’s ocular alignment. The surgeon must be able to recognize when postoperative alignment is favorable or unfavorable and should be able to advise patients on the expected postoperative course. In this chapter, we will review evaluation and management of the patient whose alignment is not satisfactory following strabismus surgery. The chapter is divided into sections based on possible etiologies of unanticipated postoperative ocular misalignment.

29.1 Prism Problems Accurate measurement of strabismus requires proper use of the prisms used to quantify the deviation. Failure to correctly use this important tool may lead to unexpected postoperative alignment. Errors in the use of prism are covered in the chapter on preoperative management errors (Chap. 18).

29.2 Unsuspected Myasthenia Gravis Myasthenia gravis is a condition that can mimic almost any ocular motility disturbance. The diagnosis should be suspected when there is a history of variable strabismus and/or variable ptosis, especially if the problem is worse toward the end of the day. Infrequently, patients will also report systemic weakness, though most patients we have treated with myasthenia gravis have had ocular signs and symptoms only. Myasthenia gravis can present as stable, unchanging, constant angle strabismus without associated ptosis. In this setting, it is virtually impossible for the strabismus surgeon to make the correct diagnosis unless the patient is already known to have the disease. Certainly it is not unreasonable to perform strabismus surgery on patients with disabling diplopia due to myasthenia gra-

vis [1, 2] and we do so routinely when the deviation appears stable. Others have reported successful surgery for patients with unstable diplopia due to myasthenia gravis [3]. We always assume that the operative outcome and stability of ocular alignment will be less stable in the long term in patients with myasthenia gravis and patients are so advised prior to surgery. On the other hand, we have operated on several patients who had exhibited, both historically and on repeated examinations, stable horizontal and/or vertical strabismus with no signs or symptoms suggestive of myasthenia gravis. Following strabismus surgery, unusual postoperative alignment was noted which included no response to surgery in one patient and a complete reversal of the deviation in another patient despite a correct surgical plan. Further diagnostic testing ultimately disclosed the true diagnosis as myasthenia gravis in these patients. While we routinely ask questions to elicit a history suggestive of myasthenia gravis in patients with strabismus, the surgeon should not be lulled into believing he/she cannot overlook a diagnosis of myasthenia gravis preoperatively.

29.3 Postoperative Duction Limitation The appearance of a duction limitation following surgery often prompts concern that a slipped or lost muscle has occurred. A mild to moderate temporary duction limitation is not uncommon in several important clinical situations and should be recognized as normal. It is not uncommon, for example, for a patient who has undergone a large recession/resection of the agonist/antagonist pair in an eye to have a duction limitation when looking toward the side of the recessed muscle postoperatively. Recession of a rectus muscle in the face of a large resection of the antagonist produces an obvious tendency for ductions in the involved eye to be limited. With time, the resected antagonist will usually gradually loosen and the duction limitation will resolve or markedly improve. The patient may experience diplopia in the field of restricted gaze and this can be of concern to patients unless its cause is explained. As stated above, small duction limitations are not uncommon during the first week or so after strabismus surgery, particularly those who have undergone resection procedures. Typically, mild limitation of ductions will be seen in the involved eye and the patient may complain of pain or discomfort

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Fig. 29.1. Limited down gaze producing diplopia in the reading position following large recession of the right inferior rectus muscle. (Courtesy of Richard A. Saunders, MD)

with large eye movements. Such apparent duction limitation in this setting is produced by discomfort and the patient’s unwillingness to stress the uncomfortable gaze position. It will usually resolve in a period of days or weeks. Treatment of strabismus in the setting of thyroid ophthalmopathy often requires very large recessions that seem out of proportion to the size of deviation. The patient in Fig. 29.1, for example, underwent a 9-mm right inferior rectus muscle recession to treat a 16 prism diopter right hypotropia. This resulted in excellent alignment in the primary position and she has achieved comfortable single vision. The trade-off was development of a moderate limitation of down gaze in the right eye with diplopia in the reading position. This can be addressed by additional strabismus surgery consisting of a posterior fixation suture to the contralateral inferior rectus muscle in an effort to balance the down gaze restrictive forces and/or the use of prism in the bifocal segment of her glasses. We typically will recommend a slab-off to induce prism in the reading position in this situation when the reading position deviation is small, and have found this to be an effective solution for many patients. Unexpected duction limitation due to a slipped, lost, or over recessed muscle or unwanted restrictive forces should be suspected when a duction limitation does not resolve within a few weeks of surgery or when it is large or atypical. Recognition and management of a slipped or lost muscle and of unwanted restrictive forces is covered in detail in Chaps. 23 and 25, respectively.

29.4 Concurrent Neurological Disease Patients with concurrent neurological disease often do not experience the same level of surgical success as patients who are not neurologically impaired. In the pediatric population,

Chapter 29

children with cerebral palsy, developmental delay, mental retardation, and other neurologic problems are more likely to have residual strabismus following surgery. For children who have significant neurologic disabilities, overcorrections are of particular concern. It is not uncommon for us to recommend a slight, empiric reduction in the surgical dose for patients with profound cerebral palsy/mental retardation to reduce this risk. In the adult population, concurrent neurological diseases that most commonly alter the results of strabismus surgery include myasthenia gravis, Parkinson disease, and multiple sclerosis, though any significant neurological condition can impart a less favorable outcome following strabismus surgery. Despite our impression that patients with neurologic disease do not fare as well following strabismus surgery, strabismus surgery can and should be offered when indicated. We recommend advising patients of their increased risk for bothersome postoperative diplopia, recurrence, and possibly a greater need for additional treatments such as prism and/or additional surgery. Adjustable sutures may be helpful in improving the immediate postoperative alignment in some patients.

29.5 Diplopia Associated with the Chiari Malformation Acute acquired esotropia and diplopia has been reported as a manifestation of Chiari I malformation [4]. A Chiari I malformation is defined as ectopia of the cerebella tonsils more than 5 mm below the foramen magnum [5]. While primary strabismus surgery can be successful, especially in patients with strabismus as an isolated finding [6], we have had several patients who developed rapid recurrence of their symptoms after strabismus surgery. Correction of a Chiari malformation may sometimes eliminate the need for strabismus surgery [4, 7]. The decision to perform neurosurgical decompression versus primary strabismus surgery should be made on a case-by-case basis in consultation with a neurosurgeon [8].

29.6 Spectacle-Induced Prism and Refractive Issues Patients with uncorrected, latent hyperopia may exhibit residual esotropia following surgery, the result of accommodative convergence. This condition should be suspected when an intermittent esotropia is seen following surgery. Ideally, cycloplegic retinoscopy should be performed on patients for whom knowledge of the refractive error could alter the surgical procedure or surgical dose.

29.6.1 Undetected Prism Many patients with small angle strabismus are initially treated with prism ground into their spectacles. Many patients may be

 

unaware or may have forgotten about earlier attempts to treat their strabismus with prism. Patients presenting with or without a known history of strabismus that has been previously treated with optical correction should have their spectacles examined to look for any evidence of prism. Omission of this relatively simple task can result in undercorrection if measurements are made without this knowledge (Chap. 18).

29.6.2 Anisometropia Patients with significant spectacle-corrected anisometropia often experience diplopia when viewing through eccentric portions of their spectacles, due to induced prism. Such patients may continue to complain of diplopia in the reading position despite achieving single vision in the primary position after surgery. The amount of induced prism can be calculated by using Prentice rule (PD = D × h, where D is the power of the lens in diopters, and h is the distance in centimeters from the optical center of the lens). This rule applies only to a single thin lens spectacle [9], but provides a reasonable estimate for more complex lenses. This problem occurs most commonly in adults who wear bifocals. The patient is often not aware of the problem prior to strabismus surgery because of the presence of diplopia in all positions of gaze. The distressed patient who has single vision in the primary position but vertical diplopia in the reading position can often be easily managed by utilization of a slab-off to eliminate or minimize the induced prism; assuming that the deviation in down gaze is relatively small.

29.7 Unsuspected Torsion, Aniseikonia, and Central Disruption of Fusion A patient with a small angle residual horizontal and/or vertical deviation who cannot fuse with correcting prism following surgery should be suspected of having one of several potential problems including torsion, aniseikonia, or central disruption of fusion.

29.7.1 Torsion In patients with large angle strabismus, it may be difficult if not impossible to accurately assess torsion preoperatively. Inspection of the fundus for objective signs of torsion may be helpful, but are no guarantee that torsion will be accurately detected. Additionally, it is very difficult to plan a surgical procedure to address torsion that is noted objectively but cannot be accurately measured. Following strabismus surgery, torsion can often be easily measured when there is little or no residual horizontal and/or vertical strabismus. Detection of torsion greater than 9–10 degrees using a double Maddox rod or other appropriate test can help to explain why a patient with small angle residual horizontal or vertical strabismus still cannot fuse despite adequate fusional amplitudes or prism.

29.7  Torsion, Aniseikonia, and Fusion

29.7.2 Aniseikonia Aniseikonia is defined as a difference in the shape and/or size of images presented to the visual cortex by the two eyes. Aniseikonia is difficult to detect both historically and during clinical examination. When the degree of aniseikonia is large it can preclude fusion. Despite this, rarely will a patient volunteer that the image size and/or shape between the two eyes is different. The surgeon must specifically inquire if it is suspected and assess the patient for the presence of aniseikonia. An eikono­ meter is an instrument used to detect and measure aniseikonia. To our knowledge, eikonometers are no longer manufactured. Clinically, a simple printed direct comparison aniseikonia test and a computerized test [10, 11] is available to analyze aniseikonia. Treatment is complex and beyond the scope of this textbook. Some simple measures that can minimize aniseikonia in spectacle-wearing patients include prescription of contact lenses and modification of spectacle lenses [12].

29.7.3 Central Disruption of Fusion Central disruption of fusion should be considered in the patient who cannot fuse despite adequate ocular alignment when there is a history of serious neurologic disease or closed head injury. It has also been reported in patients with a history of prolonged obstruction of the visual axis due to cataracts [13]. In this relatively rare condition, the patient no longer has the ability to fuse even when the eyes are properly aligned. Following seemingly successful strabismus surgery, the patient may have a small angle horizontal or vertical strabismus that is well within standard fusional ranges. Despite this, the patient experiences intractable diplopia. Upon gradual introduction of correcting prism, the patient often notes the images approaching each other and then when the images are about to become superimposed, they separate again now in opposite directions, with crossed diplopia becoming uncrossed diplopia, for example. After ruling out the presence of unsuspected torsion and of unsuspected aniseikonia, such patients are best managed through careful discussion of the problem, and if needed with monocular occlusion or with graded filters [14]. One report suggested that treatment emphasizing awareness of single vision in the periphery can be helpful [15].

29.7.4 Under- and Overcorrections Under- and overcorrections are the most common form of unexpected postoperative alignment faced by the strabismus surgeon. Although under- and overcorrections occur in a sizable minority of patients, it is unfair to list these unfavorable results as „complications.“ Under- and overcorrections are an inherent part of strabismus surgery. While careful preoperative and intraoperative measures can help to reduce the chance of needing repeat surgery, reoperations cannot be completely eliminated.

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Medical treatment of an under- or overcorrection may require the prescription of spectacles for an esodeviation in a patient with significant hyperopia, prism glasses for small deviations or temporary occlusion to eliminate diplopia. Surgical options may include the injection of botulinum toxin or additional standard incisional strabismus surgery. Assuming no other mitigating circumstances, we prefer to observe patients for a period of up to several months before making a decision to proceed with additional surgery. Often an initial over- or undercorrection will significantly improve or resolve during this period of observation. An exception to this general rule might include cases where suspicion of a slipped, lost or stretched muscle exists. In such cases, early surgical intervention is warranted.

Chapter 29 5. 6. 7.

8.

9. 10. 11.

References 1.

2.

3.

4.

Hamed LM, Challa P, Fanous MM et al (1994) Strabismus surgery in selected patients with stable myasthenia gravis. Bin Vis Eye Muscle Surg 9:283–290 Davidson JL, Rosenbaum AL, McCall LC (1993) Strabismus surgery in patients with myasthenia. J Pediatr Ophthalmol Strabismus 30:292–295 Morris OC, O’Day J (2004) Strabismus surgery in the management of diplopia caused by myasthenia gravis. Br J Ophthalmol 88:832 Lewis AR, Kline LB, Sharpe JA (1996) Acquired esotropia due to Arnold-Chiari I malformation. J Neuroophthalmol 16:49–54

12.

13.

14. 15.

Hadley DM (2002) The Chiari malformations. J Neurol Neurosurg Psychiatry 72 [Suppl 2]:ii38–ii40 Kowal L, Yahalom C, Shuey NH (2006) Chiari 1 malformation presenting as strabismus. Binocul Vis Strabismus Q 21:18–26 Defoort-Dhellemmes S, Denion E, Arndt CF, Bouvet-Drumare I, Hache JC, Dhellemmes P (2002) Resolution of acute acquired comitant esotropia after suboccipital decompression for Chiari I malformation. Am J Ophthalmol 133:723–725 Biousse V, Newman NJ, Petermann SH, Lambert SR (2000) Isolated comitant esotropia and Chiari I malformation. Am J Ophthalmol 130:216–220 Remole A (1999) Determining exact prismatic deviations in spectacle corrections. Optom Vis Sci 76:783–795 de Wit GC (2003) Evaluation of a new direct-comparison aniseikonia test. Binocul Vis Strabismus Q 18:87–94; discussion 94 Corliss DA, Rutstein RP, Than TP, Hopkins KB, Edwards C (2005) Aniseikonia testing in an adult population using a new computerized test, “the Aniseikonia Inspector”. Binocul Vis Strabismus Q 20:205–215; discussion 216 Milder B, Rubin ML (1981) The fine art of prescribing glasses without making a spectacle of yourself. Triad Scientific, Gainsville, pp 188–189 Sharkey JA, Sellar PW (1994) Acquired central fusion disruption following cataract extraction. J Pediatr Ophthalmol Strabismus 31:391–393 Rutstein RP, Bessant B (1996) Horror fusionis: a report of five patients. J Am Optom Assoc 67:733–739 Birnbaum MH (1976) Management of intractable diplopia in small angle, non-fusing squint. Am J Optom Physiol Opt 53:424–430

Chapter

Altered Postoperative Vision

30

30 Strabismus surgeons who operate on older children or adults are aware that changes in vision following surgery occur frequently. We surveyed 108 consecutive adult patients undergoing strabismus surgery and asked them to rate the subjective degree of blurred vision they experienced in the first week after surgery on a scale of 1 to 10. The average patient rated their vision as blurred to a level of 3.6 on this scale, with a range of 1 to 10. It is notable that 25% of the patients in our study rated their vision as moderately to severely impaired (>5 on a 10-point scale) in the immediate postoperative period. In many cases, we believed that the blurred vision reported was due to temporary alterations of the tear film. The vision of all of our patients returned to its preoperative level, most within 1 week after surgery. This finding has significant potential implications for many patients who wish to drive and work in the immediate postoperative period and should be discussed with patients prior to surgery. There are many potential causes of a change in vision following strabismus surgery. Vision may be temporarily altered as a normal and ordinary consequence of surgery as noted above or may be altered due to a surgical complication. Both recognized and unrecognized complications may be responsible for alteration of vision following surgery. In most cases, examination of the patient will allow rapid and accurate diagnosis of the problem. Complications that may occur during and after strabismus surgery are covered in detail in other chapters, but are briefly reviewed with respect to visual implications in this chapter. Each of the following surgical complications can produce a reduction of visual acuity or other alteration of vision. Obvious complications involving iatrogenic trauma to the anterior segment of the eye may include corneal abrasion, hyphema and corneal or lens perforation. Retinal detachment and vitreous hemorrhage may occur following perforation of the globe, though this is rare. A low lying detachment involving the macula may be more difficult to detect in the early postoperative period in a young child. Endophthalmitis following strabismus surgery is rare. However, patients with endophthalmitis may initially present with altered vision. We have seen two cases of endophthalmitis that occurred after strabismus surgery that presented with mild vitreous inflammation with little or no pain. The complaint of floaters shortly after surgery was the initial presenting symptom in both of these cases. Cases of endophthalmitis reported in the literature have been diagnosed

between 3 and 30 days after surgery. (Chap. 22) Any patient experiencing a sudden, unexpected change in vision during the immediate postoperative period should be evaluated without delay.

30.1 Anterior Segment Ischemia Anterior segment ischemia can also present in the early postoperative period with reduced vision. Reduced vision may be due to uveitis, cataract formation or a maculopathy related to hypotony of the globe. Ocular discomfort, often with accompanying photophobia, may be present. Anterior segment ischemia is more likely to occur in older patients undergoing simultaneous surgery on multiple rectus muscles. However, it can occasionally occur in susceptible younger patients and in cases where only two muscles have undergone surgery [1, 2]. Slit lamp examination of the anterior segment will often reveal anterior chamber inflammation and pupillary changes consistent with this diagnosis, including anterior chamber cell and flare and ectopia of the pupil with a poor papillary response to light. More severe cases of anterior segment ischemia may present with hyphema, hypotony, and corneal edema. The topic of anterior segment ischemia is covered in detail in Chap. 20.

30.2 Cystoid Macular Edema Cystoid macular edema has been reported following strabismus surgery in adults. Mohney and Agarwal [3] reported a case of cystoid macular edema in a 75-year-old phakic woman with no history of diabetes. Cystoid macular edema developed 2 weeks following a strabismus procedure that consisted of a recession of the lateral and superior rectus muscles in one eye. The initial complaint was a “film” that appeared to cover her vision in the involved eye. There was no indication of scleral perforation at the time of surgery or on subsequent examination by a retina specialist. Following treatment with topical and sub-Tenon’s corticosteroids, the patient’s vision returned to its measured preoperative level. The authors did not suggest an etiology for the development of this complication.

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30.3 Unrecognized Diplopia Occasional patients will complain of altered vision that they perceive as blurred. On further questioning, they may reveal that their vision improves with closure of one eye, and investigation may reveal diplopia rather than reduced acuity as the cause of the problem. This confusion is most likely to occur when the images from each eye substantially overlap (>Fig. 30.1). The borders of the image perceived by the patient may often be simply described as blurred and not recognized as double. Patients with torsional diplopia may experience similar symptoms. In some cases, torsional strabismus may have been present prior to surgery and either did not completely resolve with surgery or it was unrecognized preoperatively and thus not included in the surgical plan. Occasionally, the surgical procedure itself will introduce torsional strabismus and diplopia that was not present prior to surgery.

30.4 Change in Refractive Error A common cause for a change in vision following strabismus surgery is a change in refractive error. Changes in refractive error have been noted in several studies. Pawelec [4] described changes in the refractive error of patients undergoing strabismus surgery in 1957. He believed that these changes were secondary to alterations in the corneal power. Thompson and Reinecke [5] also noted similar changes and believed the changes that they saw were secondary to corneal changes. They reported that uncorrected astigmatism which could occur after surgery often led to a decrease in visual acuity ranging from a few letters to two lines. These changes were especially noticeable when two nonadjacent rectus muscles were operated in the same eye [5]. Other authors have reported similar findings [6–10]. The refractive error changes seen typically represent a change in astigmatism with little change in the spherical equivalent. The changes are generally transient and complete resolution can be anticipated within 6–8 weeks following surgery in most patients. However, a few patients will experience a permanent change in their refractive error [5, 11]. Corneal topography has shown that these changes consist of a steeping of the cornea along the meridian of a rectus muscle recession and flattening of the cornea in cases of rectus muscle resection [11, 12] (>Fig. 30.2). We studied the effect of the induced astigmatism produced compared with the type of surgery performed. We compared hang-back rectus muscle recession surgery with conventional surgery involving the suturing of a recessed rectus muscle directly to the sclera in its new position. The mean astigmatism induced was not different between the two groups. However, a larger number of patients undergoing conventional surgery experienced a change in astigmatism of more than 1 diopter following surgery. The results of this study suggest that patients undergoing strabismus surgery utilizing a hang-back technique may have a lower incidence of clinically bothersome induced astigmatism [13].

Fig. 30.1. Overlapping images in a patient with minimal residual strabismus is often describe by the patient as blurred vision

Although temporary changes in corneal curvature occur in the majority of patients following strabismus surgery, these changes are generally small and usually are not associated with sustained, noticeable alteration of vision. Rarely, the change in refractive error can be quite large and, more importantly, result in a significant decrease in uncorrected vision. Hutcheson [14] described a 34-year-old woman who underwent a superior rectus recession and developed an increase of more than 4 diopters of with-the-rule astigmatism. Fortunately, the induced astigmatism resolved by the third postoperative month. We have also seen occasional patients who have experienced large changes in their refractive error leading to a noticeable reduction in vision in the early postoperative period. Most patients have generally been comfortable with the reassurance that the problem will most likely be temporary. They understand that the benefit they may experience from a new glasses prescription will be short-lived and that their prescription will likely return to its preoperative state within a few weeks. Refractive error change can also occur due to development of serious surgical complications. Gross and coworkers [15] reported a case of transient high myopia that occurred in a patient who underwent a Jensen procedure and developed necrotizing scleritis postoperatively. They postulated that the problem may have been caused by an increase in the refractive index of the lens as a result of anterior segment inflammation. Hittner [16] reported a patient who developed progressive lens dislocation that resulted in marked astigmatism and amblyopia following strabismus surgery in which an eye wall perforation had presumably occurred. In summary, significant, permanent alteration of vision following strabismus surgery occurs in a minority of patients. Temporary alteration of vision is common and many patients report a moderate to marked temporary reduction in their vision in the first week after surgery. Most cases probably occur as a result of changes in refractive errors induced by changes in corneal curvature and are minimal and temporary, or there may be temporary alteration of the tear film. Other more

 

s­ erious causes occur less frequently and may be secondary to intraoperative or postoperative complications. These causes can generally be identified with a careful postoperative examination allowing treatment where warranted.

References

References 1.

2.

3. 4. 5.

6. 7.

8. 9.

10.

11.

12.

13.

Fig. 30.2. Change in corneal topography following superior rectus recession: top preoperative and bottom postoperative corneal topography. Note flattening of the superior quadrant following surgery. {Reprinted from Hainsworth DP, Bierly JR, Schmeisser ET, Baker RS (1999) Corneal topographic changes after extraocular muscle surgery. J AAPOS 3:80–86, with permission from American Association for Pediatric Ophthalmology and Strabismus [12]}

14.

15.

16.

Bleik JH, Cherfan GM (1995) Anterior segment ischemia after the Jensen procedure in a 10-year-old patient. Am J Ophthalmol 119:524–525 Murdock TJ, Kushner BJ (2001) Anterior segment ischemia after surgery on 2 vertical rectus muscles augmented with lateral fixation sutures. J AAPOS 5:323–324 Mohney BG, Agarwal S (2002) Cystoid macular edema following extraocular muscle surgery. J AAPOS 6:120–122 Pawelec M (1957) [A change of corneal refraction following ­operations for squint.]. Klin Oczna 27:603–605 Thompson WE, Reinecke RD (1980) The changes in refractive status following routine strabismus surgery. J Pediatr Ophthalmol Strabismus 17:372–374 Bartier M, Putteman A (1988) [Changes in astigmatism following surgery for strabismus.] Bull Soc Belge Ophtalmol 229:87–96 Denis D, Bardot J, Volot F, Saracco JB, Maumenee IH (1995) Effects of strabismus surgery on refraction in children. Ophthalmologica 209:136–140 Dottan SA, Hoffman P, Oliver MD (1988) Astigmatism after strabismus surgery. Ophthalmic Surg 19:128–129 Preslan MW, Cioffi G, Min YI (1992) Refractive error changes following strabismus surgery. J Pediatr Ophthalmol Strabismus 29:300–304 Wu X, Guo JQ (1992) [The effect of horizontal strabismus surgery on the refractive status in children.] Zhonghua Yan Ke Za Zhi 28:97–98 Schworm HD, Ullrich S, Hoing C, Dittus C, Boergen KP (1996) [Effect of strabismus operation of corneal topography.] Klin Monatsbl Augenheilkd 209:275–282 Hainsworth DP, Bierly JR, Schmeisser ET, Baker RS (1999) Corneal topographic changes after extraocular muscle surgery. J AAPOS 3:80–86 Betts C, Olitsky SE (2006) Effects of conventional versus hangback strabismus surgery on corneal astigmatism. IOVS 47:ARVO E-Abstract 2472 Hutcheson KA (2003) Large, visually significant, and transient change in refractive error after uncomplicated strabismus surgery. J AAPOS 7:295–297 Gross SA, von Noorden GK, Jones DB (1993) Necrotizing scleritis and transient myopia following strabismus surgery. Ophthalmic Surg 24:839–841 Hittner HM (1979) Lens dislocation after strabismus surgery. Ann Ophthalmol 11:1115–1119

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31

31 The presence of diplopia is a frequent indication for strabismus surgery. Patients naturally anticipate improvement or elimination of their double vision following surgical intervention. It is understandable that a lack of significant improvement after surgery can be a cause of considerable frustration for the patient and surgeon alike. Prolonged diplopia after surgery in a patient who did not have diplopia prior to surgery or worsening of diplopia after surgery is of greatest concern, but fortunately both are uncommon. Intractable diplopia may be particularly problematic. This chapter will review persistent diplopia following strabismus surgery. It will address which patients are at highest risk of developing persistent diplopia after surgery, with special attention to those likely to have intractable diplopia. Understanding which patients are most prone to diplopia may allow the surgeon to provide additional counseling during the informed consent process prior to surgery. This chapter will also review ways to avoid iatrogenic diplopia, which may not be treatable once it occurs. Table 31.1 lists the most common causes of persistent postoperative diplopia. Patients are often erroneously advised to avoid strabismus surgery because of the risk of constant postoperative diplopia [1]. In reality, intractable diplopia following strabismus surgery is uncommon. Kushner [2] reported on his experience of 424 adult patients who underwent strabismus surgery. Of those patients, only 9% had temporary diplopia following surgery and Table 31.1. Common causes of persistent diplopia after strabismus surgery Persistent strabismus

Overcorrection Undercorrection Untreated deviation

only 0.8% developed persistent diplopia. Cases of temporary diplopia resolved in all patients with within 6 weeks following surgery. There are several potential causes of diplopia following strabismus surgery. Temporary diplopia often occurs following surgery when there is an under- or overcorrection. Diplopia in this setting will often resolve spontaneously without the need for further treatment as postoperative misalignment spontaneously improves toward orthotropia. Patients with a history of childhood strabismus may develop suppression to eliminate their diplopia even if the postoperative deviation does not improve. This is more likely following an undercorrection, but sometimes occurs following overcorrection as well. A typical example of this would be a patient with a history of a constant exotropia. An undercorrection is unlikely to lead to postoperative diplopia because of the patient’s long-standing ability to suppress unwanted images from the temporal retina. In the case of an overcorrection, however, the image may now fall outside the existing suppression scotoma and/or retinal area in which the patient has the ability to develop suppression and diplopia is the result. Although patients who experience diplopia may wish to occlude one eye in the early postoperative period, we do not advise them to do this except at times when it is absolutely necessary, such as when they are driving or engaged in other potentially hazardous activities. The development of suppression in these patients may occur more rapidly if excessive monocular occlusion is avoided. In patients with a persistent deviation following surgery, and in those who do not develop suppression, further treatment may be necessary. When the deviation is small, prism may be helpful. For larger deviations, botulinum toxin injection or additional strabismus surgery may be required.

Incomitant strabismus Torsion Central disruption of fusion Dragged fovea diplopia syndrome Aniseikonia Spectacle induced Anomalous retinal correspondence

31.1 The Double Vision Seeking Patient Not uncommonly, patients will have single vision in the primary position and over a very large and useful range of eye positions, but will experience diplopia in extreme fields of gaze following surgery. These are often patients with a history of an incomitant strabismus in which the postoperative alignment allows for a relatively large, but not full, field of single binocular vision. Surgery may have provided an area of single

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vision larger than that which was present prior to intervention, though there remain one or more positions of gaze where the diplopia persists. Diplopia in extreme positions of gaze may also occur after surgery that creates a duction deficit and therefore incomitant strabismus, which may not have been present preoperatively. This frequently happens when a large amount of surgery is needed but must be performed on only one eye due to poor vision and the desire to avoid surgery on the “good” eye. In these situations, the diplopia frequently exists in gaze positions that are not often required for day-to-day use of the eyes. However, once the presence of double vision is recognized, the patient may have a hard time ignoring it. Helveston has suggested a useful discussion to have with patients in this situation. He describes two types of diplopia that may persist following strabismus surgery. The first is that type of diplopia which “finds” the patient. This is double vision that occurs near the primary position and is noticed by the patient during regular viewing activities. This type of diplopia will most likely continue to be bothersome and may require further treatment. The second type of diplopia is the type the patient must “find” (Helveston, personal communication). This is the type of double vision that occurs in extreme fields of gaze and does not occur under ordinary viewing conditions. Most patients will learn to adjust to this problem, and are able to avoid diplopia by moving their head to view targets outside of their field of single vision. Patients are usually reassured to know that further surgery is not only unnecessary but will most likely not completely eliminate the residual diplopia. The only time that diplopia may remain a concern in such patients on a regular basis is diplopia experienced when they must utilize their eyes to extend their field of vision beyond that which a face turn alone will achieve, such as when changing lanes or driving a car in reverse. Patients can usually adapt using other maneuvers during these times, such as momentary monocular eye closure.

31.2 Diplopia Due to Incomitant Strabismus The most common cause for intractable diplopia following strabismus surgery is an incomitant strabismus that either remains or is first noted following surgery. From a practical standpoint, the diplopia usually occurs is such extreme positions of gaze that it is well tolerated. The situation may be different for patients who have undergone surgery for restrictive or paralytic strabismus. Patients who are well aligned in primary position but who develop diplopia in positions of gaze near the primary position will usually continue to be bothered by diplopia. Their field of single binocular vision may be too small to be practically useful during common and important visual tasks. In such cases, it is not practical for the patient to adequately compensate by turning their head instead of moving their eyes. This postoperative result can often, but not always, be predicted prior to surgery. The patient who is made aware of the possibility of this problem prior to surgery is usually more tolerant of the situation.

Chapter 31

31.3 Central Disruption of Fusion (Horror Fusionis) Occasionally excellent ocular alignment is achieved with surgery but, despite this, the patient continues to experience diplopia. Patients who are incapable of experiencing single vision with normal ocular alignment have historically been referred to as having horror fusionis or central disruption of fusion. Most commonly, horror fusionis occurs following a severe closed head injury. There is usually a history of loss of consciousness. The condition has also been reported to occur following prolonged unilateral visual deprivation, such as that produced by a unilateral cataract. Pratt-Johnson and Tillson [3] described patients who developed intractable diplopia following restoration of vision following removal of unilateral cataracts. Aniseikonia was not the cause of the inability to fuse in these patients and insertion of an intraocular lens did not provide relief from the diplopia. A few patients did eventually regain the ability to fuse, although most did not. Another cause for intractable diplopia following successful alignment may be seen in some patients who have undergone orthoptic or vision training exercises as a child that included anti-suppression and diplopia awareness therapy. Although this type of therapy is used less frequently today, we continue to treat occasional adult patients who received this therapy as a child who are unable to achieve single vision once their eyes are aligned. Detailed questioning of the patient will often elicit a history of vision “exercises” consistent with anti-suppression treatment and diplopia awareness therapy. While strabismus surgery is reasonable to consider initially, the inability to obtain single vision despite sufficient alignment of the eyes within the normal physiologic ranges of fusion with or without correcting prism suggests that further treatment will be futile in our experience.

31.4 Dragged-Fovea Diplopia Syndrome The diagnosis of horror fusionis should be made with caution. Some patients will have diplopia that is not due to a disruption in central fusion and may be improved with further treatment, even though their eyes appear to be straight. The dragged-fovea diplopia syndrome has been described by De Pool and coworkers [4]. This syndrome consists of central diplopia in the presence of peripheral fusion, and is the result of displacement of the fovea in one or both eyes due to vitreoretinal disease. The central diplopia cannot be eliminated by prism therapy or with strabismus surgery. De Pool and coworkers [4] described 83 patients with the dragged-fovea syndrome. Each had metamorphopsia on Amsler grid testing or had other clinical evidence of macular wrinkling. A “lights on-off test” was reported as useful in identifying patients with this condition and is considered pathognomonic for the condition by these authors. The test is performed by directing the patient’s attention to a single white 20/70 letter on a black monitor screen. With the room lights on, the single white letter is seen as dou-

 

bled in patients with this syndrome. The room lights are then turned off and the doubled letter becomes single, usually within 2–10 s. This occurs because central fusion is the acting feedback mechanism for motor alignment under these conditions, and fusional vergence will align the corresponding foveal areas. With the room lights on, binocular vision is dominated by the stronger peripheral fusion mechanisms, which are responsible for supplying the primary feedback for motor alignment. Approximately two-thirds of the patients responded to partial monocular occlusion with satin tape placed strategically on the patient’s glasses to eliminate the unwanted central image.

31.7  Unrecognized Torsional Diplopia

31.6 Spectacle-Induced Diplopia Patients who have anisometropia and are treated with spectacles may also develop diplopia, typically only in down gaze during near work due to induced prism from their glasses. The induced prism can be eliminated through the use of a contact lens or reduced by instructing the optician to use bicentric grinding, or slab-off, in the patient’s glasses (Chap. 17).

31.7 Unrecognized Torsional Diplopia 31.5 Aniseikonia While some patients with the dragged-fovea diplopia syndrome also have evidence of aniseikonia, isolated aniseikonia can also be an unrecognized cause of postoperative diplopia. Benegas and coworkers [5] described a group of patients with macular disease who were initially thought to have disruption of central fusion but who were later recognized to be unable to fuse because of aniseikonia associated with the macular pathology. A history of macular pathology should alert the surgeon to the potential for postoperative diplopia due to macular pathology and this should be reviewed with patients prior to surgery. In rare cases, patients may prefer the widely separated images that they experience while strabismic compared with the superimposed images or very close images that occur following surgery. Though technically a patient’s surgically aligned eyes could be returned to a position near their preoperative position to alleviate their “new” symptoms following surgery, we have never had a straight-eyed patient request reversal of their surgery for this reason. Rather patients are generally happy that their eyes appear normal following surgery and are willing to utilize strategically placed monocular occluders, monocular blur, or other measures to relieve symptoms (>Fig. 31.1).

Fig. 31.1. Use of a strategically placed monocular occluder to block the unwanted image from the fovea of one eye

Patients with torsional diplopia may also be falsely identified as having central disruption of fusion. It must be remembered that diplopia occurs not only due to vertical and horizontal deviations, but also to torsional misalignment. Patients with torsional diplopia may present with objectively normal ocular alignment as measured by standard cover testing techniques, despite complaints of constant double vision. Patients often fail to spontaneously report the torsional nature of the diplopia, even if specific inquiry is made. We find a simple tool to be invaluable in helping patients to relate to us the nature of their diplopia. The patient is able to demonstrate to the surgeon exactly what he/she sees using two copies of the same diagram, one printed on paper and the second printed on a transparency (>Fig. 31.2). Torsional diplopia may occur following closed head injury due to bilateral superior oblique paresis impacting eye position only along the Y-axis of ocular rotation. The association of closed head injury with both central disruption of fusion and bilateral superior oblique paresis may make these disorders particularly likely to be confused by the clinician.

Fig. 31.2. Patients can often more easily communicate the nature and complexity of their diplopia using simple diagrams that have been printed on standard and transparent paper, respectively. In this example, the patient is demonstrating both horizontal and vertical strabismus, as well as torsional strabismus

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Torsional diplopia may also occur following retinal detachment surgery, keratoplasty, and strabismus surgery. Encircling elements placed during retinal detachment surgery may restrict or damage the superior oblique tendon, or result in damage and/or scarring of the rectus muscles [6, 7] (Chap. 27). It can be associated with thyroid disease due to involvement of both the rectus and oblique muscles [8] (Chap. 27). Kushner [9] described 15 such patients who were thought to have disruption of fusion because their diplopia could not be elimi-

nated with prisms. In 13 patients, the diplopia resolved after the cyclotropia was surgically corrected.

Fig. 31.3a–d. Red glass test for suppression and retinal correspondence. a Red filter is held before fixating the left eye. The white light stimulates nasal retina in the right eye, producing uncrossed diplopia

with esotropia. b With exotropia, the white light stimulates temporal retina of the right eye, producing crossed diplopia

31.8 Anomalous Retinal Correspondence In patients with strabismus, anomalous retinal correspondence (ARC) may develop as a compensatory mechanism to permit

 

31.8  Anomalous Retinal Correspondence

fusion of similar images projected onto noncorresponding retinal areas by objects peripheral to the area of conscious regard. Most patients with ARC exhibit instantaneous adaptation to a change in the alignment of their eyes, even as their eyes actively move from one position of gaze to another. However, if retinal correspondence is unable to adapt to the new ocular alignment produced by surgery, intractable diplopia may result. The usefulness of preoperative testing for ARC in patients undergoing strabismus surgery is unknown but may help to identify at risk patients [2, 10]. Figure 31.3 demonstrates how to test for ARC.

Fig. 31.3a–d. Red glass test for suppression and retinal correspondence (continued) c When an esotropic patient does not see an image of the white light projected to nasal retina of the deviating right eye, either suppression or anomalous retinal correspondence (ARC) is present. d A vertically oriented prism is held in front of the deviating eye to differentiate between suppression and ARC. With ARC, the

images produced will be vertically separated, but horizontally aligned (Botton). With suppression and normal retinal correspondence, the images produced will be both vertically and horizontally separated (top), as the image from the deviating eye is moved out of the suppression scotoma by the prism

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31.9 Identifying the Patient at High Risk for Intractable Diplopia

Chapter 31 Table 31.2. Patients commonly at higher risk for developing bothersome postoperative diplopia Closed head injury

Some patients are at greater risk of developing intractable diplopia following strabismus surgery than others (>Table 31.2). While identifying an increased risk of postoperative diplopia in certain patients is not usually a contraindication to strabismus surgery, identifying high-risk patients allows the surgeon to counsel such patients accordingly. It is uncommon for a patient who is motivated to have surgery and who has a higher than standard risk of developing diplopia following surgery to decide against surgical intervention. Instead, most elect to proceed with surgery and achieve excellent surgical results without bothersome diplopia.

31.9.1 Closed Head Injury Patients who develop strabismus following closed head trauma may have intractable diplopia due to a disruption in central fusion as described above. Temporary correction of the strabismus with prisms may be helpful to ascertain the likelihood of persistent diplopia after surgery. In cases where the patient has single vision with a prism in place, intractable postoperative diplopia is unlikely. Persistent diplopia despite prism correction in place does not preclude development of single vision after surgery [2]. When advised of the possibility of bothersome intractable diplopia, patients in this situation will often state that they already have double vision and therefore have nothing to lose. However, patients with large angle strabismus may not recognize that they have double vision preoperatively or may be able to easily adapt to it, the wide separation of images allowing one of the images to be easily ignored. Bringing the two images closer together with surgery can make it difficult to ignore one of the images and renders the patient symptomatic.

31.9.2 Prolonged Monocular Visual Deprivation Patients who sustain long periods of time deprived of vision in one eye are considered to be at risk of losing the ability to fuse. Should this occur and the patient’s vision is restored, intractable diplopia can develop. These same patients are at risk of developing sensory strabismus and their diplopia may initially be thought to be due solely to their ocular misalignment until their eyes are straightened surgically and the diplopia persists. Although we have yet to encounter such a patient, they have been reported in the literature. Pratt-Johnson and Tillson [3, 11] described 17 patients who lost the ability to fuse following long-standing unilateral cataracts or surgical aphakia. Each of these patients developed intractable diplopia although two patients eventually regained fusion with resolution of their diplopia. Sharkey described a similar patient who developed intractable diplopia following removal of a long-standing se-

Prolonged monocular deprivation Markedly incomitant strabismus History of anti-suppression therapy Fusing patients undergoing superior oblique surgery

nile cataract [12]. Although a rare occurrence, both the strabismus and cataract surgeon should be aware of this potential.

31.9.3 Markedly Incomitant Strabismus A patient who displays severely incomitant strabismus is, in our experience, the most likely candidate to develop bothersome diplopia following surgery. This is especially true when the orientation of the strabismic deviation changes in various fields of gaze. This is most commonly seen in patients with restrictive strabismus and may be seen following scleral buckling surgery for retinal detachment, glaucoma drainage implant surgery, thyroid-related eye disease, and other conditions that produce restrictive strabismus. Patients often are under the erroneous assumption that strabismus surgery will cure their restrictive or paralytic deviation. Preoperative discussion with the patient about the risk of continued bothersome diplopia in some positions of gaze after surgery is advisable. Such patients should be aware that it may be impossible to achieve complete resolution of diplopia even with further surgery, prism, or ­other therapy. The patient should recognize that, even with successful alignment in primary position, their field of single vision may be insufficient for all visual tasks and that that diplopia may persist in important fields of gaze. In some patients, diplopia may occur even with small excursions of the eyes away from the primary position. Surgical plans to not only achieve alignment in primary position, but to treat the associated incomitancy may expand the field of single vision, but have limited practical effect in some patients. Patients with incomitant deviations due to paralytic strabismus may also be at risk for similar postoperative problems. This is most likely to be seen when significant duction deficits involving multiple muscles is present preoperatively. Patients with third nerve palsies are a classic example. We recommend delaying ptosis surgery in these patients until after they have had a chance to experience and understand the limitations of binocular vision obtained following strabismus surgery. Some patients will find the small area of single vision achieved inadequate and may elect to forgo ptosis surgery to avoid the diplopia. We often ask patients who we think at are at particularly high risk of developing bothersome diplopia following strabismus surgery if they would be willing to tolerate monocular blur in the form of a Bangerter foil or an over plussed lens to

 

achieve relief from double vision if unable to tolerate it postoperatively. In the event of a negative answer, we recommend against strabismus surgery.

31.9.4 History of Anti-Suppression Therapy In patients with a history of eye muscle exercises which may have included anti-suppression therapy and diplopia awareness therapy, the risk of postoperative diplopia should be considered higher than in patients who have not undergone this therapy. As outlined earlier, the ability to fuse with prism correction may help to eliminate this concern but the inability to fuse with prism preoperatively is not predictive of diplopia after surgery. Kushner [2] found that patients who did not experience diplopia during preoperative testing with prisms typically did not experience persistent diplopia after surgery. He also found that the presence of preoperative diplopia with prism testing was infrequently predictive of postoperative diplopia and had a positive predictive value for persistent diplopia of only 2%. Although patients who are capable of seeing double prior to surgery may rarely continue to see double following surgery, the risk is extremely low.

31.10 Procedures Which May Induce Permanent Diplopia One of the most troublesome causes of intractable diplopia after strabismus surgery is the result of the procedure itself. Typically this occurs when the surgery results in reversal of a deviation, produces marked incomitance or results in a large torsional deviation. Most patients who have incomitant strabismus following surgery also had it prior to surgery, so that the condition should not be a surprise to the patient or surgeon. Exceptions include complications that limit ocular rotations following surgery, such as a lost muscle or restrictive strabismus due to scar formation or fat adherence. Good surgical technique reduces, but does not eliminate, the risk of these complications. New-onset torsional strabismus most commonly occurs following superior oblique surgery, usually the result of a superior oblique weakening procedure. Superior oblique tenotomy is frequently performed for treatment of Brown syndrome and for A-pattern horizontal strabismus. Santiago and Rosenbaum [13] described a series of significant complications following superior oblique tenotomy or tenectomy for Brown syndrome [13]. They described four patients who developed bothersome diplopia due to superior oblique palsies with significant torsion and an anomalous head posture. None of the patients were able to achieve relief with further surgical intervention. They suggested scrupulous adherence to the indications for surgery for Brown syndrome which include the need to treat a compensatory head posture, a deviation in primary position and, possibly, a large downshoot of the eye in adduction, and suggested alternative surgical procedures that are potentially reversible rather than tenotomy or tenectomy, such as a supe-

31.11  Managing the Patient with Intractable Diplopia

rior oblique tendon expander or the use of a “chicken suture” (Chap. 12). Superior oblique tenotomy should also be used with caution for the treatment of A-pattern strabismus and overacting superior oblique muscles in patients who have high-grade binocular vision. Parks warned against the use of this procedure in patients with bifoveal fixation [14]. He stated that an ­asymmetric result following surgery may lead to intractable torsional diplopia which cannot be treated. From a practical standpoint, this generally refers to patients with intermittent exotropia and superior oblique overaction with A-pattern strabismus. These patients may demonstrate bifoveal fixation during periods of normal alignment, an important clue to their increased risk of postoperative diplopia. Rubin and coworkers [15] reported such a case. They presented a case of a 17-yearold girl with bifoveal fixation and an A-pattern exotropia who underwent bilateral superior oblique tenectomy. She developed intrac­table torsional diplopia following surgery. At the time of second surgery, the superior oblique tendons were found to be reunited with dense surrounding connective tissues. A bilateral Harada–Ito procedure was performed which eliminated her diplopia. Lee and Rosenbaum [16] reported on the results of superior oblique weakening procedures in patients with A-pattern horizontal strabismus [16]. Of 20 patients treated, 5 had intermittent exotropia. No patient developed persistent diplopia following surgery. However, the level of binocular vision that these patients had prior to surgery was not reported. Pollard [17] has also described superior oblique tenotomy for patients with A-pattern exotropia [17]. None of the patients in his series developed intractable diplopia following surgery either. However, the preoperative sensory status of these patients was not noted in the report. To reduce the risk of postoperative diplopia in such patients having bifoveal fixation, vertical offsets of the horizontal rectus muscles may be used to help address an A- or V-pattern strabismus.

31.11 Managing the Patient with Intractable Diplopia It is inevitable that the surgeon who performs strabismus surgery on a large number of patients with complicated strabismus will eventually be confronted with a patient who has significant, intractable diplopia following surgery. With careful preoperative evaluation, the strabismus surgeon can often anticipate the possibility of this outcome and prepare the patient prior to surgery. Patients with a socially significant strabismus may be happy with the improvement achieved in their appearance and often learn to tolerate their diplopia without further surgical or optical intervention. Patients who did not recognize or were not bothered by diplopia preoperatively because of a large angle of deviation may become frustrated with their new alignment status and its associated diplopia. Fortunately, there are several options available to assist the patient with intractable diplopia that is considered refractory to additional strabismus surgery (>Table 31.3). One option is to offer diplopic patients further surgery to place their eyes back near their preoperative location. While we have occasionally made this of-

305

306

Persistent Diplopia Following Surgery Table 31.3. Treatment options for intractable postoperative diplopia Strabismus surgery to restore preoperative alignment Occlusion

Patch Bangerter foil

Contact Lens

Opaque contact lens High plus or minus power

fer to diplopic patients under these circumstances, we have yet to have a single patient exchange straight eyes for strabismus in order to eliminate their diplopia. Apparently, the desire for restoration of more normal-appearing alignment of the eyes is stronger than the desire for single vision. Occlusion of one eye is a reasonable option to treat intractable diplopia in selected patients. The option is most likely to be accepted by elderly patients who are not actively employed. Wearing a patch over one eye is generally unacceptable to patients from a cosmetic standpoint. Fortunately, a patch can be avoided in most cases. The use of a contact lens with an opaque center has been used by some ophthalmologists. We prefer the use of a high-powered contact lens to blur the image in the nondominant eye, allowing the patient to ignore the second and unwanted image. This has the advantage over an opaque contact lens in that it does not completely obstruct the patient’s peripheral vision in the treated eye. In patients who are contact lens intolerant or who cannot handle a contact lens, glasses with a frosted lens for the nondominant eye can be prescribed. Likewise, satin tape or a Bangerter foil may be placed on the glasses. Bangerter foils are available in a variety of densities. The patient should be allowed to choose the lowest density foil that renders the diplopia tolerable, while maintaining maximum possible useful vision in the nondominant eye. Each of these spectacle devices are less cosmetically noticeable than a patch. Sandy and coworkers [18] described the use of an opaque intraocular lens for the treatment of intractable diplopia in a patient with a paralytic strabismus. Although this approach may permanently treat the symptoms of diplopia, it obviously requires an intraocular procedure and precludes direct visualization of the retina. While we think that this approach is interesting, we believe that other forms of treatment are usually satisfactory and have not resorted to this approach. It has been our experience that most patients will adapt to their intractable diplopia and that it will become less bothersome with time, provided reasonable attempts to assist them have been exhausted and they recognize that further attempts are not likely to be of value. Thus an honest appraisal of the symptoms and reassurance that further treatment will not be likely to be helpful will usually suffice.

Chapter 31

References 1.

2. 3.

4.

5.

6.

7.

8.

9. 10. 11.

12.

13.

14. 15.

16. 17. 18.

Coats DK, Stager DR Sr., Beauchamp GR et al (2005) Reasons for delay of surgical intervention in adult strabismus. Arch Ophthalmol 123:497–499 Kushner BJ (2002) Intractable diplopia after strabismus surgery in adults. Arch Ophthalmol 120:1498–1504 Pratt-Johnson JA, Tillson G (1988) The loss of fusion in adults with intractable diplopia (central fusion disruption). Aust N Z J Ophthalmol 16:81–85 De Pool ME, Campbell JP, Broome SO, Guyton DL (2005) The dragged-fovea diplopia syndrome: clinical characteristics, diagnosis, and treatment. Ophthalmology 112:1455–1462 Benegas NM, Egbert J, Engel WK, Kushner BJ (1999) Diplopia secondary to aniseikonia associated with macular disease. Arch Ophthalmol 117:896–899 Cooper LL, Harrison S, Rosenbaum AL (1998) Ocular torsion as a complication of scleral buckle procedures for retinal detachments. J AAPOS 2:279–284 Wu TE, Rosenbaum AL, Demer JL (2005) Severe strabismus after scleral buckling: multiple mechanisms revealed by high-resolution magnetic resonance imaging. Ophthalmology 112:327–336 Wu HJ, Tsai RK (2004) Thyroid-associated orbitopathy with superior oblique muscle involvement: a case report. Kaohsiung J Med Sci 20:86–89 Kushner BJ (1992) Unexpected cyclotropia simulating disruption of fusion. Arch Ophthalmol 110:1415–1418 Gruzensky WD, Palmer EA (1988) Intractable diplopia: a clinical perspective. Graefes Arch Clin Exp Ophthalmol 226:187–192 Pratt-Johnson JA, Tillson G (1989) Intractable diplopia after vision restoration in unilateral cataract. Am J Ophthalmol 107:23–26 Sharkey JA, Sellar PW (1994) Acquired central fusion disruption following cataract extraction. J Pediatr Ophthalmol Strabismus 31:391–393 Santiago AP, Rosenbaum AL (1997) Grave complications after superior oblique tenotomy or tenectomy for Brown syndrome. J AAPOS 1:8–15 Parks M, Mitchell PR (1996) A and V patterns. Lippincott-Raven, Philadelphia Rubin SE, Nelson LB, Harley RD (1984) A complication in weakening the superior oblique muscle in A-pattern exotropia. Ophthalmic Surg 15:134–135 Lee SY, Rosenbaum AL (2003) Surgical results of patients with A-pattern horizontal strabismus. J AAPOS 7:251–255 Pollard ZF (1978) Superior oblique tenectomy in a pattern strabismus. Ann Ophthalmol 10:211–215 Sandy CJ, Wilson S, Brian Page A, Frazer DG, McGinnity FG, Lee JP (2000) Phacoemulsification and opaque intraocular lens implantation for the treatment of intractable diplopia. Ophthalmic Surg Lasers 31:429–431

Chapter

Medicolegal Aspects of Strabismus Surgery

32

32 This chapter will discuss the general medicolegal aspects involved in the care of the strabismus surgery patient. The goal of this discussion is to provide the strabismus surgeon a basic understanding of the medicolegal duties and implications involved in the surgical care of the strabismus patient. While some aspects of this discussion are pertinent to the general care of any medical patient, it is not the goal of this chapter to provide a detailed overview of this subject. Furthermore, this chapter should not be thought of as a legal reference with regard to this subject matter. More detailed information regarding this subject may be found in legal textbooks [1].

32.1 Informed Consent Initiation of a surgical procedure usually involves providing and obtaining informed consent from the patient or legal guardian. Informed consent is a legal concept. It provides that a patient has the right to know and understand the potential risks, benefits, and alternatives to a proposed surgical procedure. A patient’s consent is based on information that a reasonable healthcare provider would give to a reasonable patient under the same or similar circumstances in a similar practice of medicine. The basis of informed consent is that the physician has an obligation to disclose to his/her patient sufficient information that will allow the patient to evaluate a proposed surgical procedure before agreeing to submit to it. Based upon this, informed consent requires that a patient has an understanding of that procedure for which he or she has consented. A patient who authorizes a procedure but does not understand what he or she has consented to has not been given effective informed consent. It should be noted, however, that while a patient may understand at the time consent is given, it is not uncommon for patients to later forget what they have learned during the consent process. It is of paramount importance in the informed consent process that the patient adequately understands the risks, benefits, and alternatives to the procedure being proposed. The surgeon should disclose any and all risks that a reasonable person would consider important in order to decide whether or not to undergo the treatment suggested. The surgeon does not need to disclose every conceivable risk, but must discuss those risks

that a reasonable patient would expect to be informed about in order to make an adequately informed decision. In some states, law has codified specific risks of a given procedure that must be disclosed. When attempting to decide if a patient has been given adequate preoperative information, the courts generally utilize “objective” or “subjective” tests to determine if the patient would have refused treatment had the physician provided adequate information. Using an “objective test,” the plaintiff would need to prove that a reasonable person would not have undergone the procedure if he or she had been properly informed. The “subjective test” examines whether the specific “individual patient” would have chosen to proceed with the proposed procedure if given full information. In most cases the objective standard is used and it generally protects the physician from the testimony of a patient who may claim that he/she would not have consented to the procedure if fully informed of the risks by the surgeon solely to win an award. The scope of the surgeon’s duty to disclose the known risks of a procedure are measured against a reasonable medical practitioner in the same field of medicine and what he/she would have disclosed under the same or similar circumstances. Because the reasonable medical practitioner only exists in theory, the plaintiff must generally establish this standard through the use of an expert medical witness at the time of a trial.

32.2 Written Consent A written consent provides proof of a patient’s desire to proceed with a planned surgical procedure. Because the written consent is meant to provide evidence of proper informed consent, it should be incorporated into the medical record. Properly documented informed consent should include all of the elements shown in the Table 32.1. Often the surgical consent is worded in fairly general terms and should include language that a layperson can understand. It may not specifically outline in writing each of the abovementioned details. If these specific elements are not documented in the written surgical consent itself, we recommend documenting them and/or the fact that they were discussed in the office and/or hospital medical record. The general surgical consent form will document the patient’s desire to proceed

308

Medicolegal Aspects of Strabismus Surgery Table 32.1. Components of the written request for surgery (Surgical consent form) Identification of the disorder being treated Disclosure of the surgical procedure to which the patient is consenting Relevant risks and possible adverse consequences of the surgical procedure An indication that the patient understands the nature of the proposed treatment and the alternatives

with a planned surgical procedure based upon an informed consent. The medical record will allow specific documentation regarding each of the elements of the informed consent that was given and obtained. The risks of a specific surgical procedure may be applicable only to the individual strabismus surgery being performed. However, some general risks inherent to many strabismus surgical procedures may be appropriate for documentation in the medical record. In general, we discuss the risk of under- and overcorrection, the possible need for additional treatments and/or strabismus surgery, uncorrectable diplopia, infection, loss of vision, loss of the eye, and possible anesthetic complications which may include death. Likewise, general alternatives should also be discussed. Most commonly these alternatives include observation alone in appropriate cases, prism glasses if the deviation is small, and occlusion of one eye to avoid diplopia. In selected cases, consideration of botulinum toxin injection, orthoptic exercises, patching and glasses may be included as alternatives. Each of these alternatives may have its own specific advantages and risks of potential undesirable outcomes as well. We like to think of this process as documenting a request for surgery rather than consent for a surgical procedure. In other words, it should be clear from the medical documentation that the patient or parent is requesting a surgical procedure after discussing the risks, alternatives and benefits of that specific procedure and not simply consenting to the procedure as a suggestion given to them by the surgeon. Under most circumstances, and almost universally true regarding strabismus surgery, consent of the patient is required before treatment. When the patient is legally incompetent to provide consent, the consent must be obtained from a person who is empowered to consent on the patient’s behalf. The majority of strabismus procedures are performed on children. In general, children (minors) are not considered legally competent to provide consent. Consent must be obtained from the child’s parent or legal guardian. In some circumstances a ­minor may provide for their own consent. These situations may include cases where the minor is married or otherwise emancipated. Specific rules in this regard vary from state to state. When a question arises regarding the competency of a patient who needs surgery, or if there is uncertainty regarding the person who may legally provide consent, it may be best to discuss the situation with an attorney.

Chapter 32

32.3 Medical Malpractice A tort is a civil or personal wrongdoing. A wrongdoing can be both intentional and due to negligence. For wrongdoing to be considered intentional, it must not only be committed intentionally but the person performing the act must realize to some degree that harm could result. An intentional wrongdoing also willfully violates another person’s interest. A negligent wrongdoing does not require that an act is committed. A wrongdoing may include failure to act when the person, in the case of medical malpractice a physician, had a duty to act.

32.4 Intentional Torts 32.4.1 Battery Battery is the intentional touching of another person in an impermissible manner, without the person’s consent. Battery is an intentional act that violates the physical security of another person. It may occur even if the receiver of the battery is not aware that the offense has been committed. Battery may occur when a wrong-site surgery takes place or when a surgical procedure is performed in the absence of a properly obtained surgical consent. Other egregious examples of battery might include imprinting the initials of the surgeon in the retina with a laser or otherwise engaging in improper conduct during surgery.

32.5 Unintentional Torts Negligence is an unintentional wrongdoing. It consists of an unintentional commission or omission of an act that a reasonable person would have done or not done under the same or similar circumstance. Surgical negligence consisting of a commission of an act might include performing a surgical procedure without a patient’s consent, or performing a procedure on the wrong patient or on the wrong body part. These acts would also be considered battery. Negligence is conduct caused by carelessness, which departs from a standard of care. Surgical malpractice may occur when a professional performing surgery commits an act of negligence. The forms of negligence include:  Malfeasance: execution of an unlawful or improper act  Misfeasance: improper performance of an act  Nonfeasance: failure to act when there is a duty to act. There are two degrees of negligence:  Ordinary negligence: failure to do what a reasonable person would or would not do  Gross negligence: intentional omission of care that would have been proper to provide.

 

32.5.1 Elements of Negligence In order for negligence to exist, the following four elements must be present: (1) duty to care, (2) breach of duty, (3) injury, (4) causation. All four elements must be present in order for a patient to recover damages suffered as a consequence of a negligent act. Duty to care requires the existence of a relationship between the surgeon and patient. A duty exists based in part on the request for surgery form (consent form) reviewed and signed between the patient and operating surgeon prior to surgery. The duty to care exists not only as a responsibility to provide care but also to provide care in an acceptable manner. This is often defined as the standard of care. In recent rulings, the courts have been less likely to rely on a community standard and more likely to apply a national standard when making a determination about the standard of care. For a breach of duty to exist, there must be a deviation from the standard of care. An expert witness generally provides interpretation of the standard of care at the time of trial. An injury must take place for a defendant surgeon to be considered liable. A surgeon may be negligent but may not be held responsible for damages if an injury does not occur. However, the definition of injury is not limited to a physical harm. It may also include loss of income or reputation as well as compensation for emotional distress, pain, and suffering. Likewise, the occurrence of an injury does not itself establish the presence of negligence. Harm or injury may occur secondary to an unavoidable complication, which did not represent a deviation from the standard of care. Finally, the fourth element necessary to establish a case of negligence requires that there is a causal connection between the surgeon’s negligent action and the resulting damages suffered by the patient.

32.6 The Medical Record The medical record provides an archive of information if a question arises regarding the medical care provided to a patient. For this reason, it is important to document the basic content of both the examinations and the discussions that take place between the physician and patient. It should be recognized, however, that the medical record only represents a thumbnail sketch of examination findings, discussions, and recommendations. Its primary purpose is to support ongoing care of the patient and to act as a mechanism of communication to other physicians and medical personnel. While tampering with a medical record may send a wrong signal to a jury,

32.7  The Unhappy Patient

it is permissible to alter a medical record when new information is obtained or if a mistake made in an earlier patient encounter is recognized. If a circumstance occurs where a change or addendum is needed in the medical record, the existing note should not be destroyed or erased. A single line should be drawn through the statement(s) needing to be changed so that the prior information is still legible. A new statement should then be entered. Optimally, the change should be dated and signed/initialed by the person making the change. In an electronic medical record environment, these elements are generally automated and while a record can be amended, it is generally not possible to remove information from the record once the record has been electronically signed. It should be remembered that it is often easier to explain why a detail may have been left out of the medical record erroneously than to add or alter information once its absence is considered potentially damaging.

32.7 The Unhappy Patient Even the most experienced and most thoughtful strabismus surgeon will eventually encounter a patient who is unhappy with his/her services. An occasional patient may even threaten legal action. Often the source of unhappiness is an unexpected or undesirable surgical outcome. Preoperative planning and discussions with the patient can help to reduce the risk of an unwanted outcome and can help to reduce the patient’s distress when an unwanted outcome occurs. Surprise over a bad outcome may be more likely to be associated with a decision to pursue medicolegal action than is the bad outcome itself [2]. It has been our experience that most patients who experience an undesirable outcome or adverse event appreciate a surgeon who is both sympathetic and honest with them. They also recognize when someone has tried their best to correct the problem, even if this means referring the patient to another doctor who may have more experience in dealing with the problem. In contrast, if the patient perceives their surgeon to be uninterested, uncaring, defensive and/or dishonest, they are much less likely to be tolerant of an unwanted outcome.

References 1. 2.

Pozgar G (2004) Legal aspects of health care administration, 9th edn. Jones and Bartlett, Boston, Mass. Bettman J (1990) Seven hundred medicolegal cases in ophthalmology.. Ophthalmology 97:1379–1384

309

Subject Index

A A-pattern, offsetting horizontal rectus muscles for  96 A-pattern; procedures for  96, 124 A-pattern and down slanting fissures  4 Abducens nerve, functions  15 Abducens nerve paralysis, surgery for  131–138 Aberrant regeneration of oculomotor nerve, surgical considerations  261–262 Abscess; subconjunctival  197, 230 – treatment of  230 AC/A ratio, high, treatment of with posterior fixation sutures  156–157 Access,surgical and palpebral fissures  1 Accessory Muscle  273–274 Accommodative esotropia – bifocals and  166 – optical treatment of  165 – surgical indications  165 Accommodative esotropia, bifocals and  166 Accommodative paralysis; after inferior oblique surgery  200 Actions of the extraocular muscles  24–26 Adhesions, conjunctival  197–198 Adjustable sutures – bow-type technique  145 – bucket handle suture and  142 – cinch knot technique  145 – general principles  141–142 – in children  141, 145 – indications  141 – lower eyelid retractors  260–261 – ripcord technique  145–149 – surgical modifications to facilitate  141 – timing of adjustment  141 – traction knot technique  145 Advancement of the eyelids after vertical rectus resection  259 Agyrosis  200 Amyloidosis  198, 282 Anesthesia – general anesthesia  48 – general anesthesia; induction of  48 – Intraoperative awareness  287 – preoperative medications  48 – retrobulbar and peribulbar  49

– retrobulbar and peribulbar, complications of  247, 287–288 – sub-Tenon’s, complications of  248, 288 – sub-Tenon’s infusion  49 – topical  49 – topical, complications of  288 – topical; modification of surgical technique  50 Anesthesia awareness, unintentional  287 Aniseikonia, as cause of diplopia  293, 301 Anomalous head posture. see compensatory head posture Anomalous retinal correspondence  302 Anterior ciliary arteries  15 – normal anatomy  208 – surgical techniques to spare  207–208 Anterior oblique anterior transposition procedure – indications  113–114 – techniques  114–115 Anterior segment; blood supply  203–204 Anterior segment ischemia  204 – alternative procedures  206, 208 – blood supply of the anterior segment  203–204 – botulinum, role of  206–207 – classification of  205 – clinical presentation  205 – development of collateral blood flow  204 – incidence  204 – prevention of  206–209 – risk factors  204–205 – staging of surgery  209 – techniques to spare anterior ciliary vessels  207–208 – treatment of  205–206 Antibiotics, postoperative  225–227 Aplasia of eye muscles  267–271 – craniofacial syndromes; strabismus and  267–268 – of the horizontal rectus muscle  271 – of the inferior oblique muscle  269 – of the inferior rectus muscle  270–272 – of the superior oblique tendon/muscle  268, 272 – of the superior rectus muscle  271 Astigmatism, as surgical complication  296 Augmented full tendon transposition  133 Awareness during anesthesia, unintentional  287 Axes of rotation  21–22 Axial length, impact on surgery  88

312

Subject Index

B Bacterial endocarditis, prophylaxis for  231 Battery  308 Bilateral surgical dose  37, 38 Blood supply to the anterior segment  203–204 Blood supply to the extraocular muscles  15 Blowout fracture, occult  279 Botulinum neurotoxin – complications of  163, 218 – for over and under correction after surgery  162 – history of  159–160 – injection techniques  160–161 – in sensory strabismus  162 – mechanism of action  159 – overview of strabismus treatment success  161–162 – treatment of nystagmus  162–163 Brown syndrome – acquired  280 – complications of superior oblique tendon expander  128, 255 – due to superior oblique tucking procedures  119–120 – surgery for  124–128 Bucket handle suture, for adjustable sutures  142 Buckley augmented full tendon transposition  134 Burns to eyelids  265–266 C Capsulopalpebral head, and adjustable sutures  260–261 Cardinal positions of gaze  23 Cataract, as complication of strabismus surgery  200 Cellulitis – orbital  227–229 – orbital, signs and symptoms  227–228 – preseptal  227–229, 265 Central disruption of fusion  293 Cerebral palsy, and strabismus  292 Chemosis, treatment of  191–192 Chiari malformation and strabismus  292 Classification of slipped and lost muscles  233 Compensatory head posture – and concurrent strabismus, surgery for  29–30, 174 – and nystagmus, surgery for  31, 174 – isolated ocular torticollis, surgery for  156–157 Concurrent strabismus and non-strabismus surgery  231 Concurrent systemic illness at time of strabismus surgery  230–231 Congenital fibrosis syndrome – surgery for  281 – with ptosis and pseudoptosis  7, 263 Conjunctial recession, technique  82 Conjunctiva – adhesions, after strabismus and eyelid surgery  197 – anatomy of  7 – button holes  198 – histology  7 – incision options  72–74 – landmarks, surgical  16, 67

– plica semilunaris conjunctiva  7 – structure  7 Consent, informed  307 Consent, written consent components  307–308 Conversion from fornix to limbal incision  83 Corneal abrasion  186 Corneal endotherial cell count; reduced after strabismus surgery  188 Corneal topography; changes after strabismus surgery  296 Corneal ulcer  186–188, 230 – and reduced corneal sensation  187 – prevention of after surgery for oculomotor nerve palsy  187 Coronal synostosis, strabismus and  4–5, 268–269 Craniofacial syndromes and strabismus  4–5, 267–268 Cryotherapy, after eye wall perforation  218 Cyst, epithelial inclusion – and muscle complications  194 – etiology  194 – prevention  194–195 – treatment of  197 Cyst; sudoriferous  196 D Dellen, corneal  185–186 Dellen, scleral  200–201 Denervation and extirpation of inferior oblique  113 Diagnostic positions of gaze  24 Diplopia, at risk patients  304 – closed head injury  304 – incomitant strabismus  304–305 – previous anti-suppression therapy  305 – prolonged monocular visual deprivation  304 Diplopia, intractable, management of  305–306 Diplopia, post operative  299 – due to aniseikonia  293, 301 – due to anomalous retinal correspondence  302–303 – due to central disruption of fusion  293, 300 – due to dragged-fovea diplopia syndrome  300–301 – due to horror fusionis  300 – due to incomitant strabismus  300 – due to torsion  293, 301 – spectacle-induced  301 Diplopia seeking patient  299–300 Dissociated strabismus and inferior oblique overaction, surgery for  113 Donder’s law  23 Dragged-fovea diplopia syndrome  300–301 Draping; surgical  57–58 Duane syndrome – eyelid changes following surgery  262 – transposition surgery for  131 Duction limitation, in infantile esotropia  176 Duction limitation, postoperative  291–292 Duction movements  22

 

E Education, of the patient postoperatively  43–45, 227 Endophthalmitis  224 – clinical presentation  225, 228 – etiology  224–225, 226 – incidence  224 – preoperative systemic infections  225, 230 – prognosis  225 – prophalatic antibiotics, role of  225–227 – scleral perforation and  224, 228 – treatment of  225, 226 Epithelial inclusion cyst. see cyst; epithelial inclusion Esodeviations – bilateral surgical dose  38 Examination, ocular motor system  36–37 Excylotorsion, treatment with Harada-Ito procedure  122–124 Exodeviations – bilateral surgical dose  38 – unilateral surgical dose  38 Expander, superior oblique tendon, complications of  255 Extraocular muscles, actions of  24–26, 25 Eyelid advancement. see advancement, eye lids Eyelid changes – adhesions, after lid and strabismus surgery  264–265 – following Foster procedure  262 – following horizontal rectus surgery  262 – following inferior oblique anterior transposition  264 – following vertical rectus muscle surgery  259–261 – in duane syndrome  262 – ptosis, following routine strabismus surgery  263 – strabismus induced  6–7 – thermal injury  265–266 Eyelid retraction. see retraction, eyelids F Facial asymmetry, superior oblique palsy and  4 Fadenoperation  156 Fasting recommendations, preoperative  47 Fat adherence syndrome – etiology  253 – prevention  254–255 – treatment  255 Fick’s axes of rotation  21–22 Field of single vision; surgical considerations  173 Filamentary keratitis  188 Footplates, rectus muscles  12 Foreign body; subconjunctival; post operative  198 Fornix incision  73–80 – advantages/disadvantages  73–74 – closure of  79–80 – converting to a limbal incision  83 – dissection of fascia  76–77 – exposure of muscle  76–77 – location of  74 – pole test  76 Fourth cranial nerve. see trochlear nerve

Subject Index

Fracture, orbital. see orbital fracture Free tenotomy of a rectus muscle  96 Full tendon transposition, for rectus muscle paralysis  133–134 – foster modification  133 – vessel sparing  134–135 G Gass hook  61, 106 Glaucoma setons, strabismus following  279–280 Gloves, surgical  64, 223 – perforation of  223 Grey spot, post operative  198 H Hang-back recession rectus muscles – general principles and technique  92–94 – measurement of  94–95 Harada-Ito procedure – classic approach  124 – Fells modification  122–123 – with adjustable sutures  123–124 Heal or toe maneuver, after hooking rectus muscle  76 Heavy eye syndrome.  154–156, 280–281 Hemi-hang back recession; rectus muscles  95–96 Hemorrhage – eyelid  247 – from vortex veins  250 – garlic and ginko bulbo (check spelling)  250 – herbal medicines  250 – intraocular  250 – muscle  249–250 – retrobulbar, decompression for  248 – retrobulbar, following injection  248 – retrobulbar, lateral canthotomy for treatment of  248 – risk factors  247 – subconjunctival  250 Herring’s law of equal innervatoin  23 Hibiclens corneal toxicity  188 High myopia associated strabismus; etiology & treatment of  154–156, 280–281 History taking; preoperative  35 Hummelsheim transposition procedure  135 Hummelsheim transposition procedure, Augmented  135–136 Hydrogel explants and strabismus  279 Hyperthermia, malignant  285–286 Hypertropia, surgical dose  38 Hyphema, as complication of surgery  200, 219, 250 I Incisions; conjunctival  72 – choice of, for rectus muscle surgery  72–73 – fornix incision  73–78 – for oblique muscle surgery  86

313

314

Subject Index

– swan incision  84–85 Indications for strabismus treatment  32 – asthenopia  28 – asymptomatic patients  29 – compensatory head posture  29–30 – diplopia  28 – expansion of field of vision  30 – facial asymmetry; in superior oblique palsy  5, 30 – incomitant deviation  28 – miscellaneous  30 – nystagmus  30 – psychosocial considerations  31–32 – restoration of binocular vision  27 – vocational considerations  31–32 Infection; post operative; risk factors  223 Inferior oblique anterior transposition – eyelid changes following  264 – Technique  113–115 Inferior oblique inclusion syndrome  255 Inferior oblique muscle – actions of  25–26 – double – bellied  272 – surgical anatomy  18–19 – traction testing  71 Inferior oblique muscle, surgery on – advancement of  116 – anterior and nasal transposition  115 – anterior transposition  113–115 – denervation and extirpation  113 – disinsertion  111 – dissection of fascia  107 – general principles   105 – graded recession  109 – inclusion syndrome  255–256 – isolating muscle  106–107 – mydriasys and paralysis of accommodation, post operative  200 – myectomy  112 – nasal myotomy  115 – recession  109 – spontaneous reattachment after myectomy  109 – traction testing  71 – traction testing, failure to detect residual inf oblique  272 – tucking procedures  116 – weakening procedures, choice of  109 Inferior oblique muscle overaction, surgery for  108–115 Inferior oblique myotomy  112 Inferior rectus muscle – actions of  24–25 – surgical anatomy  17 Informed consent  307 Infratarsal lower eyelid retractor lysis  261 Instruments; surgical – Gass muscle  61, 105 – locking 0,5 mm forceps  61 – Scobee muscle hook  62 – typical set up  58–60 Iris angiography  204

J J-Deformity of rectus muscle  256 Jensen procedure  136–137 – Partial tendon transposition, of rectus muscles  136–138 Jensen procedure, vessel-sparing technique  137 K Keratitis, filamentary  188 Knapp transportation procedure  136 L Laboratory testing; pre anesthesia  47 Laser photocoagulation, after eye wall perforation  218 Lashes; isolation of  57 Lateral canthotomy technique  248 Lateral rectus muscle – actions of  24–25 – surgical anatomy  16 Lid splitting procedure for surgical access to superior rectus  276 Lights on/off test for dragged-fovea diplopia syndrome  300–301 Limbal incisions – advantages/disadvantages  79 – closure of  81, 190–191 – conjunctiva, recession of  82 – dissection of fascia  80 – locations of  80 – modified  82 – technique  80 Listing’s plane  21–22 Locking suture bites  238 Loss of vision. see Vision loss, as complication of surgery Lost rectus muscles – classification of  233 – clinical presentation and diagnosis  238–239 – following non-strabismus surgery  238 – intraoperative loss  239–240 – Lost rectus muscles  241–242 – neuroimaging and  241–242 – pulled in two syndrome (PITS)  240–241 – repair of  242–243 – transposition procedures for treatment of  243 – traumatic disinsertion of  242 Lower eyelid retractors; adjustable sutures  260–261 M Magnification; for surgery  64–65 Malignant hyperthermia  285–286 Malposition of muscle after resection, correction of  101 Malpractice, medical  308 Marginal myotomy of inferior oblique muscle  112 Marginal tenotomy/myotomy, of rectus muscle  153–154 Marking surgical site  182 Measurement artifacts, during recession surgery

 

– due to caliper  88 – due to muscle insertion artifacts  88 Measurement errors; strabismus – due to duction limitation  180 – due to poor cooperation  181 – due to poor fixation  181–182 – due to spectacles  178, 180 – Krimsky and Hirshberg tests  177 – primary position errors  177 – prism addition errors  178, 179 – prism position  177–178 Medial rectus muscle – actions of  24, 25 – surgical anatomy  16 Medical record, the  309 Monocular diplopia, etiology  173 Monocular elevator deficiency, surgery for  136 Monocular patients; strabismus surgery on  231 Monofixation syndrome  27 Muscle-tendon rupture, during surgery  240–241 Muscle insertion artifacts, rectus muscles  88 Muscle malposition after resection, correction of  101 Muscles, extraocular, actions of  24–26 Myasthenia gravis, unsuspected  291 Mydriasis, after inferior oblque surgery  200 Myectomy; inferior oblique  111–112 Myectomy of inferior oblique, Spontaneous reattachment after  109 Myopexy, retroequatorial  156 Myopia associated strabismus; etiology & treatment of  154–156, 280–281 Myotomy; inferior oblique  112 N Nausea and vomiting; post operative  51, 286–287 – in children  52 – prevention and treatment of  51 Needles; surgical – choice of  62–63 – design features  62–63 – ideal characteristics  62–63 Neglect, elements of  309 Neo-synephrine. see phenylephrine Neuroimaging, and strabismus  11, 12, 241–242, 270 Neurologic disease; concurrent with strabismus  292 Non-surgical treatment of strabismus  166–169 – bifocal lenses, for accommodative esotropia  166 – occlusion therapy for exotropia  166–167 – occulsion, diplopia relief  167 – orthoptic therapy  167–168 – over minus lens therapy  166 – prism therapy  168–169 – refractive correction  165–166 Nystagmus – Anderson procedure  30 – four-muscle recession  30 – Kestenbaum procedure  30

Subject Index

– null zone  30 – treatment with botulinum neurotoxin  162–163 Nystagmus with strabismus; treament of  174 O Oblique muscle overaction, surgery for. see specific muscle Ocular respiratory reflex  53 Oculocardiac reflex – adjustable sutures and  53 – neural pathway  52 – prevention  52 – risk factors  52 Oculomotor nerve, aberrant regeneration, surgical considerations  261 Oculomotor nerve, functions  15 Oculomotor nerve, neurovascular bundle  113, 115 Oculomotor nerve paralysis, surgery for – periosteal flap procedure  151–152 – recession and periosteal fixation of lateral rectus to orbital wall  151–153 – rectus muscle transposition for paresis  133–137 – superior oblique tendon transposition  138–139 Operating room lay out  58 Orbital decompression; as treatment for retrobulbar hemorrhage  248 Orbital fat, relationship to posterior Tenon’s capsule  253 Orbital fractures, occult  279 Orthoptic therapy  167–168 Over correction, after surgery  161–162, 291–292 Overmunus lens therapy for exodeviations  166 P Pain; post operative – management of  53–54 – severity of  54 Palpebral fissures – and surgical access  3 – down-slanting  4 – upslanting  4 Partial tendon transposition, of rectus muscles – four-fifths transposition, vessel sparing  135 – Hummelsheim procedure  135 – Hummelsheim procedure, augmented  135–136 Perforation; scleral – clinical evidence of  217–218 – cryotherapy, complications of  218 – definitions  211 – effect of needle design  212–214 – endophthalmitis and (see also endophthalmitis)  219, 228 – following posterior fixation sutures  216 – hemorrhage and  218–219 – incidence  211–212 – prevention  219–220 – prevention; special surgical techniques  214 – retinal detachement and  218 – risk factors  212, 214–216

315

316

Subject Index

– treatment  220 Periosteal fixation of rectus muscle  151 Periosteal flap fixation procedure  151, 208 Phenylephrine (neosynephrine), use prior to surgery  217 Physiology, of eye movements  21–26 plagiocephaly  4–5 Plica advancement; inadvertent  188–189 – prevention of  189–190 – treatment of  190–191 Pole test, after hooking rectus muscle  76 Posterior fixation suture – indications for  156 – mechanism of action  156 – scleral perforation and  216 – techniques  156–157 Posterior fixation sutures, using pulley fixation  216 Postoperative care considerations – antibotic administration  43 – patient instructions; adult  45 – patient intructions; child  43 – timing of follow-up  43 Povidone-iodine preparation  57 Pre operative management errors – paralytic strabismus; unrecognized  174 – prism use errors: see prisms, for measureing strabismus  177 – restriction; unrecognized  174 – torsion, unrecognize  175 – undetected prism  292–293 Preoperative patient preparation  57 Preparation for surgery  41–42 Preseptal cellulites  227–229, 265 Prism, spectacle induced in anisometropia, calculation of  293 Prism, spectacle induced measurement of  178–180 Prism; spectacle-induced  178–180 Prism; unrecognized in spectacles  180–182 Prisms, for measuring strabismus – addition of bilateral prism  177, 179 – addition of stacked prism  178, 179 – prism orientation errors  176 Prisms and anisometropia  293 Prism therapy – calculating oblique prism  168–169 – prescription tips  169 Pseudo-strabismus – pseudo-esotropia  5 – pseudo-exotropia  6 – pseudo-hypertropia  6 Pseudoduction deficits  176–177 Pseudoptosis, with congenital fibrosis  7, 263 Psuedo-oblique overaction in exotropia  176 Ptosis, postoperative, as complication of surgery  259–261, 263 Ptosis, post operative, related to corticosteroids use  263 Ptosis, with congenital fibrosis  263 Pulled in two syndrome (PITS)  240–241 Pulley system; rectus muscles

– function of  11 – heterotopic and strabismus  272–273 – rectus muscle paths  10 – structure of  10–11 Pyogenic granuloma  193 R Recession, inferior oblique  109 Recession, rectus muscle without scleral sutures  214 Recession; inferior oblique, graded recessions  109 Recession of superior oblique tendon  128 Recession of the conjunctiva  82 Recession surgery, rectus muscles – general principles  87 – hang-back technique  92–95 – hemi-hang back technique  95–96 – inferior rectus; special considerations  88–89 – in patients with thin sclera, techniques  214, 282 – insertion artifacts  88 – lateral rectus; special considerations  89 – medial rectus; special considerations  88 – superior rectus; special considerations  89 – techniques, standard  89–92 – without scleral sutures  214 Record keeping  309 Rectus muscle procedures – free tenotomy  96 – marginal tenotomy/myotomy  153–154 – recession surgery  87–97 – resection surgery  99–102 – transposition procedures  131–138 – tucking procedures  102–103 Recuts muscles – abnormal insertions  273–274 – actions  24 – anatomy of  12 – anterior ciliary arteries  15 – blood supply  15 – distance of insertion from limbus  12, 13 – head or toe maneuver, to confirm surgical isolation of muscle  75 – identification of insertion; tactile  15, 67 – identification of insertion; visual  15, 67 – inferior rectus; surgical anatomy  17 – isolation of, during surgery  75 – lateral rectus; surgical anatomy  16 – medial rectus; surgical anatomy  16 – recession procedures  87–97 – resection procedures  99–103 – superior rectus; surgical anatomy  17–18 – tenotomy of  96 Refractive correction, and strabismus  166–167, 292–293 Resection; rectus muscles – dual suture technique  101 – general principles  99 – resection clamp technique  102 – tucking procedures  102–103

 

Restrictive strabismus, undiagnosed preoperative  39 Retinal detachement; after strabismus surgery  218 Retinal detachment; after botulinum injection  218 Retraction of lower eyelids after surgery – after inferior rectus recession  259 – incidence of  259 – prevention  259–261 Retraction of the conjunctiva, after surgery  191 Retraction of upper eyelids after superior rectus recession  259 Retrobulbar anesthesia, complications of  287–288 Retrobulbar hemorrhage  248 Retrobulbar hemorrhage, treatment of  248 Retroequatorial myopexy  156 S Scarring between Tenon’s capsule and conjunctiva  256 Sclera, thin, suggested surgical modifications  282 Scleral buckle, strabismus following – etiology  277–278 – hydrogel explants and  279 – muscle erosion by buckle  277 – surgery for  277 Scleral needle pass, minimum requirements  92 Scleral perforation. see perforation, scleral Scleral plaques  282 Scleral ridge  199 Scleral thickness  7, 8 Scleral thinning, visible post operative  198 Scleritis  200, 229–230 Sedation, preoperative  48 Sherrington’s law of reciprocal innervation  23 Silcone expander, for superior oblique tendon  127–128 Sixth cranial nerve. see abducens nerve Skin preparation; pre operative  57 Slipped rectus muscles – clinical presentation  233–235 – etiology  233 – neuroimaging appearance  234 – prevention of  237–238 – repair of  237 – signs of  235 – step test  235 Spiral of Tillaux  12 Split rectus muscle, inadvertent  76 Spring back test for lost and slipped muscles  71, 234–235 Staging of surgery, in patients at risk for anterior segment ischemia  209 Step test for slipped muscles  235 Strabismus with nystagmus; treatment of  174 Stretched scar syndrome  243 – as a cause of overcorrection after surgery  243–246 – clinical presentation  243–244 – differentiating from slipped muscle  244 – treatment of  244–246 Sub-Tenon’s infusion of anesthetic  49 Sub-Tenon’s infusion of anesthetic, complications of  248

Subject Index

Sudoriferous cysts, postoperative  196 Superior oblique, surgery on – adjustable sutures and  123–124 – Harada-Ito procedure, classic approach  124 – Harada-Ito procedure, Fells modification  122–123 – identification and isolation of tendon  120–121 – posterior tenotomy/tenectomy  128–129 – recession  128 – silicone expander of superior oblique tendon  127–128 – tenectomy  126 – tenotomy  126 – tenotomy, guarded  126 – transposition of the tendon  138–139 – tuck  121–122 Superior oblique muscle/tendon – actions  25 – aplasia of tendon, treatment of  268 – congenital anomalies of tendon  272–273 – surgical anatomy  18 – tendon laxity  71 – traction testing of  69–72 Superior oblique muscle overaction, surgery for  124–129 Superior oblique tendon transposition  138–139 Superior rectus muscle; – actions  24–25 – surgical anatomy  17–18 Surgical dose, bilateral, for horizontal strabismus  37, 38 Surgical dose, unilateral, for horizontal strabismus  38 Surgical dose, vertical strabismus  38 Surgical planning – adjustable sutures  39 – incomitant strabismus  39 – number of muscles to operate  36–37 – surgical dose  37, 38 – torsional diplopia  39 – which eye to operate  36 Sutures – absorable  63–64 – collagen  63–64 – ideal characteristics  63 – mono and multi-filament  63 – nonabsorbable  64 – synthetic  64 Swan incision  84–86 Systemic illness at time of strabismus surgery  230–231 T Tenon’s capsule – episcleral (sub-Tenon’s) space  9 – function  9–10 – relationship to extraocular muscle  9–10 – structure  9 Tenon’s capsule, prolapse of, postoperative  193 Tenotomy, free, of rectus muscles  96 Tenotomy/tenectomy of superior oblique tendon  126 Tenotomy/tenectomy of superior oblique tendon, guarded  126

317

318

Subject Index

Tenotomy/tenectomy posterior; superior oblique tendon  128 Third cranial nerve. see oculomotor nerve Thyroid ophthalmopathy – exotropia in  276 – lid splitting procedure for surgical access of superior rectus muscle  276 – oblique muscle involvement  274 – superior rectus involvement  275–277 – surgery for  275–276 – surgical modifications for  278 Tillaux, Spiral of  12 Torsion, isolated; surgery for  122–124, 156 Torsion, unrecognized preoperatively  175 Torts  308 Traction sutures; postoperative  153 Traction testing  67 – failure to detect residual inferior oblique muscle  272 – on the inferior oblique muscle  71 – on the rectus muscles  67–69 – on the superior oblique, technique  69–72 Transposition surgery  131 – anterior segment ischemia risk  131 – augmented full tendon  133–134 – conjunctival incisions for  132–133 – four-fiths transposition  135 – full tendon  133 – general principles  131 – goals of surgery  131 – Hummelsheim procedure  135 – Hummelsheim procedure, augmented  135–136 – indications  131 – Jensen procedure  136–137 – Jensen procedure, vessel sparing  137 – Knapp procedure  136 – mechanism of action  131 – of the superor oblique tendon  138 Trochlear nerve, functions  15 Trochlear nerve paralysis, surgery for

– inferior oblique weakening procedures  105–115 – superior oblique strengthening procedures  119–124 Tucking procedures, for rectus muscles  102–103 Tucking procedures, for superior oblique tendon  121–122 U Under correction, after surgery  161–162, 293–294 Unhappy patient, the  309 Unilateral surgical dose  37, 38 V V-pattern; offsetting horizontal rectus muscles for  96, 106 V-pattern and up slanting fissures  4 Vergence movements  22 Version movements  22 Vertical deviations, surgical dose  38 Vertical rectus muscles, actions  24–25 Vision loss, as complication of surgery  218, 225, 295–297 Visual alterations after strabismus surgery – due to anterior segment ischemia  295 – due to changes in refractive error  296 – due to cystoid macular edema  295 – due to unrecognized diplopia  296 Visual alterations after strabismus surgery due to altered corneal topography  296–297 Vitreous hemorrhage  218–219 Vomiting, postoperative. see nausea and vomiting, postoperative Vortex veins  17, 19, 89, 107 – hemorrhage from  250 Y Y-splitting of lateral rectus muscle  97 Yoke muscles  22

Erratum Strabismus Surgery and its Complications edited by David K. Coats and Scott E. Olitsky ISBN 978-3-540-32703-5

The drawings in this book have been created by Susan Gilbert, Certified Medical Illustrator, St. Petersburg, FL, USA.