Atlas of Optical Coherence Tomography for Glaucoma [1st ed.] 9783030467913, 9783030467920

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Atlas of Optical Coherence Tomography for Glaucoma

Donald L. Budenz Editor

123

Atlas of Optical Coherence Tomography for Glaucoma

Donald L. Budenz Editor

Atlas of Optical Coherence Tomography for Glaucoma

Editor Donald L. Budenz University of North Carolina at Chapel Hill Chapel Hill, NC USA

ISBN 978-3-030-46791-3    ISBN 978-3-030-46792-0 (eBook) https://doi.org/10.1007/978-3-030-46792-0 © Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, 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. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Writing books and book chapters as an academic physician is a labor of love. There is little to no compensation, books and chapters do not appear on PubMed or improve one’s H-index, and it takes a lot of time. So why do it? It is really to meet an unmet educational need. When I published my first book Atlas of Visual Fields in 1997, there were excellent textbooks teaching the fundamentals of performing and interpreting visual fields but clinicians were still struggling with interpreting visual fields. It was actually a retina sub-subspecialty colleague, Alexander J.  Brucker, MD, who pitched the idea to the publisher and recommended me for the project. He pointed out that visual field interpretation is a visual task and having an atlas of many figures and just enough words to teach the reader how to interpret them was a better way to teach. Of course, we do this at continuing educational meetings all the time but those meetings only reach the participants in the room whereas a book can have worldwide readership and improve patient care for many more people. The same concept motivated me to put together this Atlas of Optical Coherence Tomography for Glaucoma. Except, 23 years later, I am arguably a little wiser and realized I could get good friends to write the chapters so it would not be so much work for me. I have probably given over 100 lectures on OCT in glaucoma to trainees and eye care providers and taught several thousand eye care providers how to perform and interpret OCT scans, but there was no single high-quality atlas addressing this and the chapters in other atlases were, in my opinion, too superficial to be helpful. Therefore, my hope is that this atlas will teach the reader OCT interpretation for glaucoma in a visual fashion, with only enough words to help the reader understand how to interpret the images presented. I hope that we have achieved our goal using an enjoyable case-based approach that can be consumed in a relatively short amount of time. I am indebted to the authors of this atlas, all dear friends and colleagues who have taught me a lot as I had the pleasure of editing their chapters. I am also thankful to my wife of 40 years, Sue, who remains a true Proverbs 31 woman. Chapel Hill, NC, USA  Donald L. Budenz v

Contents

1 Fundamentals of OCT for Glaucoma����������������������������������������������������    1 Alangoya Tezel, Joel S. Schuman, and Gadi Wollstein 2 What Makes for a Good OCT for Glaucoma?��������������������������������������   11 Jean-Claude Mwanza and Donald L. Budenz 3 Retinal Nerve Fiber Layer Analysis in Glaucoma��������������������������������   31 Angelo P. Tanna 4 Optical Coherence Tomography Optic Disc Parameters for Glaucoma��������������������������������������������������������������������������������������������   61 Jean-Claude Mwanza and Donald L. Budenz 5 Macular Parameters for Glaucoma��������������������������������������������������������   77 Yong Woo Kim and Ki Ho Park 6 Anterior Segment OCT in Glaucoma����������������������������������������������������   97 Carlos J. Vives Alvarado, Kimberly A. Mankiewicz, and Nicholas P. Bell 7 OCT Progression Analysis����������������������������������������������������������������������  113 Christopher Kai-shun Leung 8 Red and Green Disease in Glaucoma ����������������������������������������������������  127 Elli A. Park, Donald L. Budenz, Richard K. Lee, and Teresa C. Chen 9 Challenging Case Studies Using OCT����������������������������������������������������  175 Hady Saheb and Andrew Crichton 10 Emerging OCT Technologies for Glaucoma������������������������������������������  187 Karine D. Bojikian, Joanne C. Wen, and Philip P. Chen Index�������������������������������������������������������������������������������������������������������������������� 201

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Contributors

Nicholas  P.  Bell, MD  Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA Karine  D.  Bojikian, MD, PhD  Department of Ophthalmology, University of Washington, Seattle, WA, USA Donald  L.  Budenz, MD, MPH  University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Philip  P.  Chen, MD  Department of Ophthalmology, University of Washington, Seattle, WA, USA Teresa  C.  Chen, MD  Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA Andrew  Crichton, MD  Department of Surgery, Division of Ophthalmology, Faculty of Medicine, University of Calgary, Calgary, AB, Canada Yong Woo Kim, MD  Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea Richard  K.  Lee, MD, PhD  Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA Christopher  Kai-shun  Leung, MD  Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Hong Kong, China Kimberly A. Mankiewicz, PhD  Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA Jean-Claude Mwanza, MD, MPH, PhD  University of North Carolina at Chapel Hill, Chapel Hill, NC, USA ix

x

Contributors

Elli A. Park, MD  Boston University School of Medicine, Boston, MA, USA Ki  Ho  Park, MD  Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea Hady  Saheb, MD  Department of Ophthalmology, McGill University, Montreal, QC, Canada Joel  S.  Schuman, MD  Department of Ophthalmology, NYU Langone Health, New York, NY, USA Angelo  P.  Tanna, MD  Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA Alangoya Tezel, MD  Department of Ophthalmology, NYU Langone Health, New York, NY, USA Carlos  J.  Vives  Alvarado, MD  Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA Joanne C. Wen, MD  Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA Gadi Wollstein, MD  Department of Ophthalmology, NYU Langone Health, New York, NY, USA

Chapter 1

Fundamentals of OCT for Glaucoma Alangoya Tezel, Joel S. Schuman, and Gadi Wollstein

Introduction Optical coherence tomography (OCT) is an imaging technique that uses interferometry to reconstruct three-dimensional cross-sectional images of tissue. Interferometry is a group of techniques that use interference patterns to measure displacement. More specifically, OCT operates through optical interference, or the phenomenon wherein two light waves come together to create a single waveform (Fig. 1.1). In an OCT system, light from a coherent, broadband light source is split in two by a beam splitter [1]. Part of the light travels along the reference arm and is back-­ reflected by a reference mirror. The rest of the light travels along the sample arm and enters some media, such as the eye. Returning light from both arms is recombined at the beam splitter to generate an interference pattern that is later recorded by a detector. In newer OCT models, this interference pattern is detected by a spectrometer and undergoes a Fourier transform in order to reconstruct images of tissue. Today, OCT systems all operate under this same principle of interferometry. Though invented only three decades ago, OCT has quickly become the standard of care for glaucoma. As demonstrated in Table 1.1, OCT systems employ different wavelengths, detectors, and scanning protocols [2–5] to fill distinct clinical niches. In this chapter, we present high-quality images from different OCT manufacturers to explore the impact of different scanning protocols on the visualization and measurement of anatomical features of the optic nerve head (ONH) and macula (Figs. 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.10, 1.11, and 1.12).

A. Tezel · J. S. Schuman · G. Wollstein (*) Department of Ophthalmology, NYU Langone Health, New York, NY, USA e-mail: [email protected] © Springer Nature Switzerland AG 2020 D. L. Budenz (ed.), Atlas of Optical Coherence Tomography for Glaucoma, https://doi.org/10.1007/978-3-030-46792-0_1

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Fig. 1.1  Basic OCT system. A laser light beam is emitted toward the eye and a reference arm. Back-reflected light from both arms is matched to generate an optical cross section of the imaged location

Reference

Light source

Beam splitter

Detector

Table 1.1  Comparison of four different commercially available OCTs Manufacturer Type of OCT Light source

Scan beam wavelength (nm) Scanning speed (A-lines/second) A-scan depth (in tissue) Axial resolution (optical) Transverse resolution (optical) Reproducibility of average RNFL thickness measurements in healthy eyes (CV%)

Spectralis Heidelberg Engineering Spectral-domain

Cirrus 5000 Zeiss

Avanti Optovue

Triton Topcon

Spectral-domain

Spectral-domain

40,000

27,000–68,000

70,000

100,000

1.8 mm 7 μm

2 mm 5 μm

~3 mm 5 μm

2.6 mm 8 μm

14 μm

15 μm

15 μm

20 μm

1.45

2.38

1.54

2.40

Swept-­ source Superluminescent Superluminescent Superluminescent Tunable diode diode diode swept laser 870 840 840 1050

CV = coefficient of variance

Raster Cube Scan: ONH Raster cube scans are a commonly used OCT scan pattern (Fig. 1.2). By sweeping in a zigzag fashion, raster cube scans are able to generate three-dimensional images of areas of interest. In the example above, the different iteration of the OCT devices offers different visualizations of the retinal layers. Cirrus 5000 (Fig. 1.3a), being a spectral-domain OCT, uses a superluminescent diode with a central wavelength of approximately 840 nm. Triton (Fig. 1.3b), being a swept-source OCT, uses a tunable swept laser with a central wavelength of approximately 1050  nm. This longer

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Fig. 1.2  Schematic of raster cube scan (ONH)

a

b

Fig. 1.3  Raster cube scan of the optic nerve head. (a) Cirrus 5000. Scanning protocol: 200 A-scans × 200 B-scans (40,000 points) over 6 mm × 6 mm area. (b) Triton. Scanning protocol: 512 A-scans × 256 B-scans (131,072 points) over 6 mm × 6 mm area

central wavelength allows for swept-source devices to penetrate more deeply through the retinal pigment epithelium (RPE).

Multiline Raster Scan: Macula Multiline raster scans are obtained by acquiring repeated scans along each B-scan in only a few locations (Fig. 1.4). Averaging the repeated scans in each B-scan reduces the background noise level and improves the visualization of the tissue. This combination provides highly detailed visualization but in limited locations. Both Spectralis (Fig. 1.5a) and Cirrus 5000 (Fig. 1.5b) employ this scan pattern for macular scans.

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Fig. 1.4  Schematic of multiline raster scan (macula)

Fig. 1.5  Multiline raster scan of the macula. (a) Spectralis. Scanning protocol: averaging of up to 100 B-scans with 1024 A-lines per B-scan. (b) Cirrus 5000. Scanning protocol: 5 parallel B-scans (6 mm each) with 1024 A-lines per B-scan, scanned and averaged 4 times

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Circular Scan: ONH The circular scan is often used in the context of glaucoma (Fig. 1.6). By circling a roughly 3.45 mm diameter around the optic disc, circular scans offer reliable sampling of retinal ganglion cell axons as they travel through the retinal nerve fiber layer on their way from the entire retina toward the optic nerve head. Note that for this scanning pattern, only the Spectralis circular scan (Fig. 1.7a) employs averaging of the repeated B-scans, while the Cirrus 5000 circular scan (Fig. 1.7b) does not employ this averaging.

Radial and Radial-Concentric Scan: ONH The radial scan (Fig. 1.8) provides high scanning density at the center (center of the optic nerve head in OHD scan or fovea in macula scan) and sparse sampling in the periphery. For this reason, radial scans, like those of Avanti, are often coupled with a circular scan at the radial lines’ periphery in order to increase scanning density. This is referred to as the radial-concentric scan (Fig. 1.9). However, due to the relatively long time gap between the time of acquisition of the radial and the concentric scans, this scan pattern is prone to eye movement that reduces the repeatability of measurements acquired by this scan pattern. The “smooth” image quality of Spectralis (Fig. 1.10a) and the “grainy” image quality of Avanti (Fig. 1.10b) are also Fig. 1.6  Schematic of circular scan (ONH)

6 Fig. 1.7  Circular scan of the peripapillary region of the optic nerve head. (a) Spectralis. Scanning protocol: average of three circumpapillary scans spanning a 12-degree arc (roughly 3.45 mm diameter depending on axial length). (b) Cirrus 5000. Scanning protocol: extracted from raster cube scan, 200 A-scans × 200 B-scans (40,000 points) over 6 mm × 6 mm area

A. Tezel et al.

a

b

Fig. 1.8  Schematic of radial scan (ONH)

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Fig. 1.9  Schematic of radial-concentric scan (ONH)

a

b

Fig. 1.10  Radial scans of the optic nerve head. (a) Spectralis. Scanning protocol: 24 radial lines with 3.4-mm scan length (768 A-scans each) and 7.5-degree interval. (b) Avanti. Scanning protocol: 6 concentric rings and 12 radial lines with 3.4-mm scan length (452 A-scans each) and 15-degree interval

the result of different image-processing techniques. Spectralis averages up to 100 B-scans to create one image. By contrast, Avanti does not employ this averaging, and the scan is completed in a shorter scanning time.

Wide-Field Scan: ONH and Macula Using wide raster scans, the wide-field scan captures both the macula and optic disc in a single scan, making it a versatile tool for clinicians (Fig.  1.11). The scans above both have the same field of view (12 mm × 9 mm). Differences in

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Fig. 1.11  Schematic of wide-filed scans (ONH and macula)

a

b

Fig. 1.12  Wide-field scans of the optic nerve and macula. (a) Avanti. Scanning protocol: 320 A-scans × 320 B-scans (102,400 points) over a 12 mm × 9 mm area. (b) Triton. Scanning protocol: 512 A-scans × 256 B-scans (131,072 points) over a 12 mm × 9 mm area

the visualization of structures, particularly the choroid, are a result of the different imaging techniques used by the devices, such as the longer central wavelength employed by Triton. Avanti (Fig. 1.12a) is a spectral-domain OCT, and Triton (Fig.  1.12b) is a swept-source OCT with improved signal from deeper layers.

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References 1. Fujimoto JG, Pitris C, Boppart SA, Brezinski ME. Optical coherence tomography: an emerging technology for biomedical imaging and optical biopsy. Neoplasia (New York, NY). 2000;2(1–2):9–25. 2. Wu H, de Boer JF, Chen TC. Reproducibility of retinal nerve fiber layer thickness measurements using spectral domain optical coherence tomography. J Glaucoma. 2011;20(8):470–6. 3. Hong S, Kim CY, Lee WS, Seong GJ. Reproducibility of peripapillary retinal nerve fiber layer thickness with spectral domain cirrus high-definition optical coherence tomography in normal eyes. Jpn J Ophthalmol. 2010;54(1):43–7. 4. González-García AO, Vizzeri G, Bowd C, Medeiros FA, Zangwill LM, Weinreb RN. Reproducibility of RTVue retinal nerve fiber layer thickness and optic disc measurements and agreement with stratus optical coherence tomography measurements. Am J Ophthalmol. 2009;147(6):1067–74. 5. Hong EH, Ryu SJ, Kang MH, Seong M, Cho H, Yeom JH, Shin YU. Comparison of repeatability of swept-source and spectral-domain optical coherence tomography for measuring inner retinal thickness in retinal disease. PLoS One. 2019;14(1):e0210729.

Chapter 2

What Makes for a Good OCT for Glaucoma? Jean-Claude Mwanza and Donald L. Budenz

Optical coherence tomography (OCT) has rapidly been adopted as an important tool for diagnosing glaucoma and monitoring of glaucoma progression. OCT may be especially helpful in distinguishing glaucoma suspects from early glaucoma since it may detect earlier glaucoma-related damage than visual field testing. In addition to findings of clinical examination, accurate diagnosis of glaucoma and timely detection of its progression require good interpretation of OCT scans, which should fulfill a number of requirements. Since its introduction, spectral domain OCT (SDOCT) has been undergoing hardware and software improvements that continue to improve its performance. As a result, segmentation of different structures and measurements have become more and more precise. However, these improvements have not eliminated the possibility of artifacts that affect the quality of OCT scans [1–4]. Low-­ quality scans, if not recognized by the technician or the clinician, can affect the interpretation and lead to misdiagnosis of glaucoma, misclassification of its stage, or misdiagnosis of its progression. It is therefore critical for clinicians to remain alert for possible artifacts when interpreting OCT outputs, particularly because a single scan can have more than one type of artifact [5]. A good quality scan for glaucoma should be free of any type of artifact.

J.-C. Mwanza (*) · D. L. Budenz University of North Carolina at Chapel Hill, Chapel Hill, NC, USA e-mail: [email protected] © Springer Nature Switzerland AG 2020 D. L. Budenz (ed.), Atlas of Optical Coherence Tomography for Glaucoma, https://doi.org/10.1007/978-3-030-46792-0_2

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Table 2.1  Signal strength range and normal cutoff for 6 SDOCT devices Device Spectralis (Heidelberg Engineering) Cirrus HD-OCT (Carl Zeiss Meditec) RTVue (Optovue) 3D-OCT (Topcon) RS-300 (Nidek) Copernicus HR (Optopol Technologies)

Range 0–40 0–10 0–100 0–100 1–10 0–10

Normal ≥15 ≥6 ≥30 ≥45 ≥7 ≥6

Types of OCT Artifacts There are several types of OCT artifacts that, if not recognized, may lead to misinterpretation and misdiagnosis [6].

Low Signal Strength This refers to any value of signal strength below the device manufacturer’s recommended minimum threshold as shown in Table 2.1. Signal strength is a key output to assess when examining and interpreting OCT scans because a less than optimal level can negatively affect the rendering of the anatomic structure being examined and the related measurements. Low signal strength most commonly results from cataract [7–9] (Fig. 2.1) and dry eye [6, 10], but all media opacities such as corneal scar (Fig. 2.2) may reduce the signal strength. When signal strength degrades, the retinal nerve fiber layer (RNFL), ganglion cell-inner plexiform layer (GCIPL), and ganglion cell complex (GCC) are measured thinner than they actually are. Correct measurements may be obtained after cataract removal or corneal lubrication using artificial tear drops. Blocked signal can also be caused by the edge of the pupil (Fig. 2.3), dirty OCT lens, and vitreous floaters.

Out-of-Range Scan Also called “out of register artifact,” it refers to an OCT scan that has moved outside the scanning range during image acquisition so that part (upper or lower) of the OCT image is cut out (Fig. 2.4). This artifact is often observed in highly myopic eyes. It may also be seen in non-myopic eyes as a result of poor image acquisition by the operator (i.e., misalignment of the scan). Because a part of the scan is outside the frame, the built-in software will be unable to detect and identify the boundaries

e

d

Deviation from Normal map

[µm] [µm]

T

c

T

f

N

106

I

59

N

88

I

S

Mean (TSNIT): TSNIT std dev : 85

0

50

100

150

200

250

300

71

S

Mean (TSNIT): TSNIT std dev : 98

0

50

100

150

200

250

300

S

T

79 µm 21 µm

T

89 µm 29 µm

S

N

N

68

58

60

88 - 153

72

53

73

88 - 153

97

71

1%

110

87

1%

RNFL TSNIT

103

87

I

4%

136

108

I

4%

62

97

90%

73

80

65

T

5%

55

T

5%

52

100

90%

Fig. 2.1  Copernicus OCT scans of the left eye with cataract in a 71-year-old man otherwise healthy. The images were taken 5 years apart. The baseline OCT images showed ONH measurement within normal range, apparently normal RNFL thickness on the thickness map (a), thinner RNFL on the deviation map (b), and abnormal TSNIT profile despite the overall average being normal (c). The follow-up images shown in d, e, and f display thinner RNFL than at baseline due to cataract progression (Courtesy of Dr. Nilgun Solmaz, Ophthalmology Clinic, Haseki Training and Research Hospital, Istanbul, Turkey)

b

a

RNFL thickness map

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a

b

c *** Low Test Relability *** GHT Outside normal limits

30

VFI

66%

MD

-13 04 dB P 5% Within Normal

SN

p