Comparison of retinal thicknesses measured using swept-source and spectral-domain optical coherence tomography devices

Comparison of retinal thickness measurements among four different optical coherence tomography devices

We sought to compare the retinal thickness measurements collected using different optical coherence tomography (OCT) devices. This prospective study included 21 healthy cases, and the retinal thickness was measured using the PLEX Elite (Carl Zeiss Meditec, Dublin, California, USA), DRI OCT-1 Atlantis (Topcon Corp, Tokyo, Japan), Cirrus 5000 HD-OCT (Carl Zeiss Meditec), and Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany), respectively. The mean central retinal thickness (CRT) and mean retinal thickness of the Early Treatment of Diabetic Retinopathy Study (ETDRS) area were compared. The CRT varied significantly among the different OCT devices (P < 0.001). Post-hoc analysis revealed that the CRT measured using PLEX Elite (278.95 ± 20.04 µm) and Spectralis (271.86 ± 17.92 µm) were similar, and both were greater than the CRT measurements of DRI OCT-1 (239.57 ± 21.06 µm) and Cirrus (256.76 ± 17.82 µm). Additionally, the mean retinal thickness in each ETDRS area showed significant differences among the four devices (all P < 0.001). The mean retinal thickness measured varied according to the device used, and this needs to be considered when comparing retinal thickness measurements taken with different devices.

Association of retinal neurodegeneration with the progression of cognitive decline in Parkinson's disease

Retinal thickness may serve as a biomarker in Parkinson's disease (PD). In this prospective longitudinal study, we aimed to determine if PD patients present accelerated thinning rate in the parafoveal ganglion cell-inner plexiform layer (pfGCIPL) and peripapillary retinal nerve fiber layer (pRNFL) compared to controls. Additionally, we evaluated the relationship between retinal neurodegeneration and clinical progression in PD. A cohort of 156 PD patients and 72 controls underwent retinal optical coherence tomography, visual, and cognitive assessments between February 2015 and December 2021 in two Spanish tertiary hospitals. The pfGCIPL thinning rate was twice as high in PD (β [SE] = -0.58 [0.06]) than in controls (β [SE] = -0.29 [0.06], p < 0.001). In PD, the progression pattern of pfGCIPL atrophy depended on baseline thickness, with slower thinning rates observed in PD patients with pfGCIPL below 89.8 µm. This result was validated with an external dataset from Moorfields Eye Hospital NHS Foundation Trust (AlzEye study). Slow pfGCIPL progressors, characterized by older at baseline, longer disease duration, and worse cognitive and disease stage scores, showed a threefold increase in the rate of cognitive decline (β [SE] = -0.45 [0.19] points/year, p = 0.021) compared to faster progressors. Furthermore, temporal sector pRNFL thinning was accelerated in PD (βtime x group [SE] = -0.67 [0.26] μm/year, p = 0.009), demonstrating a close association with cognitive score changes (β [SE] = 0.11 [0.05], p = 0.052). This study suggests that a slower pattern of pfGCIPL tissue loss in PD is linked to more rapid cognitive decline, whereas changes in temporal pRNFL could track cognitive deterioration.

Normative data and repeatability for macular ganglion cell layer thickness in healthy Swedish children using swept source optical coherence tomography

BACKGROUND

Optical coherent tomography (OCT) technology is evolving with improved resolution and accuracy in segmentation between different cell layers in the retina. The ganglion cell layer in the macula region is a window to see what is happening in the visual pathways and a macula OCT is an examination that most children tolerate. This makes updated normative data necessary since variables may differ between different OCT devices and normative data for children is often not presented. The aim of this study was to develop normative data for macular ganglion cell layer thickness in children, measured with swept source OCT, and investigate the repeatability between measurements.

METHODS

Healthy Swedish children between 4 and 16 years old, with normal refraction, spherical equivalent mean:1.13 (sd:0.66) dioptre and normal visual acuity Logmar, mean: 0,015 (sd:0,05), were examined with swept source OCT. Macula OCT was performed three times in both eyes and the different retinal layers were evaluated.

RESULTS

Fifty-eight children were screened for inclusion. Fifty-five children were included in the study, 24 boys and 31 girls. Mean age was 8.9 years. Results from right eyes was analysed. The mean average thickness of macular ganglion cell layer thickness, retinal nerve fibre layer/ganglion cell layer boundary to inner plexiform layer/inner nuclear layer boundary, was 68.0 μm (sd:4.0, range:58-77). There was no correlation with sex or age. Fifty-three children manage to complete two, and 41 children three acceptable measurement and the mean coefficient of variation was low.

CONCLUSION

The ganglion cell layer thickness differs according to which OCT device that is used, and the population examined. This makes normative data essential to accurately interpret results. Swept source OCT of the macula have excellent repeatability and the examination well tolerated in most children making it an investigation useful for diagnosing and following diseases in the optic pathways.

Agreement Between Spectral-Domain and Swept-Source Optical Coherence Tomography Retinal Thickness Measurements in Macular and Retinal Disease

INTRODUCTION

To assess inter-device agreement in optical coherence tomography-derived retinal thickness measurements in patients with known macular conditions between spectral-domain and swept-source optical coherence tomography (OCT).

METHODS

Two hundred seventy-two subjects were included in the study. They consisted of 91 male (33.5%) and 181 female (66.5%) subjects, and 132 left (48.5%) and 140 right (51.5%) eyes. Each subject underwent spectral-domain OCT (SD-OCT, Spectralis, Heidelberg Engineering; RTVue XR Avanti XR HD, Optovue) and swept-source OCT (SS-OCT; DRI-OCT-1, Atlantis, Topcon) in a single imaging session performed by the same clinical trial-certified technician. The comparison of retinal thickness reproducibility between devices was performed using Bland-Altman analyses and across the entire data set using the intraclass correlation coefficient (ICC).

RESULTS

The ICC of the retinal thickness measurements (95% confidence interval) made using all three OCT instruments was 0.81 (0.77-0.84). The mean difference in mean retinal thickness between Spectralis SD-OCT and Topcon SS-OCT was 59.1 μm (95% limit of agreement [LoA] -21.7 to 139.8 μm). The mean difference in mean retinal thickness between Optovue SD-OCT and Topcon SS-OCT was 21.8 μm (95% LoA -34.7  to 78.3 μm).

CONCLUSIONS

Retinal layer thickness measurements vary between SS-OCT and SD-OCT devices. We describe inter-device agreement in retinal thickness between SS-OCT and SD-OCT in patients with macular conditions. Clinicians should be aware of the differences in retinal thickness values when imaging patients using different OCT devices and should consider using the same OCT device model in order to monitor clinical change.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier (NCT02828215).

Tortuosity Index Calculations in Retinal Images: Some Criticalities Arising from Commonly Used Approaches

A growing body of research in retinal imaging is recently considering vascular tortuosity measures or indexes, with definitions and methods mostly derived from cardiovascular research. However, retinal microvasculature has its own peculiarities that must be considered in order to produce reliable measurements. This study analyzed and compared various derived metrics (e.g., TI, TI_avg, TI*CV) across four existing computational workflows. Specifically, the implementation of the models on two critical OCT images highlighted main pitfalls of the methods, which may fail in reliably differentiating a highly tortuous image from a normal one. A tentative, encouraging approach to mitigate the issue on the same OCT exemplificative images is described in the paper, based on the suggested index TI*CV.

Retrospective Analysis of Treatment Patterns in Pseudophakic Diabetic Macular Oedema Eyes Treated with Anti-VEGF

Methods

We performed a retrospective review of outcomes in 81 pseudophakic eyes with DMO that received at least 6 anti-VEGF injections. We reviewed baseline and posttreatment optical coherence tomography images, visual acuity, prescribing patterns, time taken to deliver anti-VEGF injections, and structural and functional outcomes.

Results

It took an average of 913 ± 454.1 days to deliver a mean of 11.1 ± 4.7 anti-VEGF injections. Time from baseline to receiving the first 6 anti-VEGF injections was longer than 9 months in 74.7% (n = 59/79) of eyes. There was a mean gain of 1.6 letters (−0.03 logMAR) from baseline to the end point. After 5 anti-VEGF intravitreal injections, the mean CMT was 391.9 μm from 474.4 μm at baseline (p < 0.0001). In 52 of 79 eyes (65.8%), more than one type of anti-VEGF agent was used.

Conclusions

The anti-VEGF treatment used to treat these eyes with DMO was suboptimal, a finding consistent with recently published “real-world” data. There was a strong tendency for patients to be switched within the class to a second anti-VEGF agent.

Changes in retinal layers in type 1 diabetes mellitus without retinopathy measured by spectral domain and swept source OCTs

To evaluate changes in inner retinal layer (IRL) thicknesses in patients with type 1 diabetes mellitus (DM1) with no diabetic retinopathy (DR) using two different optical coherence tomography (OCT) devices. Ninety DM1 and 60 healthy eyes were evaluated using spectral domain (SD)-OCT and swept source (SS)-OCT to measure changes in the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and inner nuclear layer (INL) thicknesses in all Early Treatment of Diabetic Retinopathy Study (ETDRS) macular areas. Functional tests were performed in both groups, including ETDRS with 100, 2.5 and 1.25% contrast, and color vision. The mean ages were 42.93 ± 13.62 and 41.52 ± 13.05 years in the diabetic and control groups, respectively. Visual acuity (VA) with ETDRS 1.25% was lower in the DM1 patients. Both ETDRS 2.5% and color vision were lower in the DM1 group but did not reach statistical significance. Retinal thicknesses in the central area and in the vertical outer areas were higher in the DM1 group. Differences were found in the IRL with no changes in the outer ones. Long-term DM1 patients with no DR maintained visual function, with a decrease in VA with 1.25% ETDRS contrast. Macular thickness measurements were higher using Spectralis SD-OCT than DRI Triton SS-OCT, and DM1 patients had a decrease in IRL thickness, especially in the GCL at the parafoveal level, generating thinning of the RNFL in the peripheral areas. There were no differences in outer retinal layer (ORL) thickness.

Comparison of Macular Thickness Measurements Using Swept-Source and Spectral-Domain Optical Coherence Tomography in Healthy and Diabetic Subjects

Purpose: To establish normative data for macular thickness in Chinese aged 30 to 80 years using the swept-source optical coherence tomography (SS-OCT) device.Methods: The study included 290 normal eyes, 430 NDR eyes and 150 DR eyes of community residents aged 30 to 80 years in Guangzhou, China. Mean macular thicknesses in Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, central point thicknesses (CPT), and macular volume was measured by SS-OCT (Triton DRI OCT, Topcon, Tokyo, Japan) and Spectral-Domain OCT (SD-OCT; Heidelberg Engineering, Heidelberg, Germany). We assessed agreement between SS-OCT and SD-OCT measurements by intraclass correlation coefficients (ICC) and Bland-Altman plots. We established a conversion equation relating central subfield (CSF), CPT and macular volume between the two OCT devices.Results: Macular thickness measurements in SS-OCT were significantly thinner than in SD-OCT. The mean CSF thickness in normal eyes measured by SS-OCT and SD-OCT were 227.8 ± 19.4 μm and 260.0 ± 19.7 μm (p < .0001). CSF thickness was a significantly difference between genders (SS-OCT: male 237.2 ± 18.8 μm vs female 222.0 ± 17.5 μm, p < .0001). In all three groups, the agreement between SS-OCT and SD-OCT was excellent (all ICC > 0.9). The conversion equations for CSF, CPT and macular volume from SS-OCT to SD-OCT were derived, with over 95% of the predicted values fell within 10% of the actual measurements in DR and NDR eyes.Conclusion: We propose SS-OCT CSF thicknesses of 275 μm for males and 260 μm for females as the minimum criteria for macular edema in Chinese aged 30 to 80 years based on 2 SDs above the mean CSF. SS-OCT measurements were significantly thinner than SD-OCT. We derived equations from converting SS-OCT measurements to SD-OCT equivalents.

En face image-based classification of diabetic macular edema using swept source optical coherence tomography

This retrospective study was performed to classify diabetic macular edema (DME) based on the localization and area of the fluid and to investigate the relationship of the classification with visual acuity (VA). The fluid was visualized using en face optical coherence tomography (OCT) images constructed using swept-source OCT. A total of 128 eyes with DME were included. The retina was segmented into: Segment 1, mainly comprising the inner nuclear layer and outer plexiform layer, including Henle’s fiber layer; and Segment 2, mainly comprising the outer nuclear layer. DME was classified as: foveal cystoid space at Segment 1 and no fluid at Segment 2 (n = 24), parafoveal cystoid space at Segment 1 and no fluid at Segment 2 (n = 25), parafoveal cystoid space at Segment 1 and diffuse fluid at Segment 2 (n = 16), diffuse fluid at both segments (n = 37), and diffuse fluid at both segments with subretinal fluid (n = 26). Eyes with diffuse fluid at Segment 2 showed significantly poorer VA, higher ellipsoid zone disruption rates, and greater central subfield thickness than did those without fluid at Segment 2 (P < 0.001 for all). These results indicate the importance of the localization and area of the fluid for VA in DME.

Reliability of Retinal Pathology Quantification in Age-Related Macular Degeneration: Implications for Clinical Trials and Machine Learning Applications

Purpose

To investigate the interreader agreement for grading of retinal alterations in age-related macular degeneration (AMD) using a reading center setting.

Methods

In this cross-sectional case series, spectral-domain optical coherence tomography (OCT; Topcon 3D OCT, Tokyo, Japan) scans of 112 eyes of 112 patients with neovascular AMD (56 treatment naive, 56 after three anti-vascular endothelial growth factor injections) were analyzed by four independent readers. Imaging features specific for AMD were annotated using a novel custom-built annotation platform. Dice score, Bland-Altman plots, coefficients of repeatability, coefficients of variation, and intraclass correlation coefficients were assessed.

Results

Loss of ellipsoid zone, pigment epithelium detachment, subretinal fluid, and drusen were the most abundant features in our cohort. Subretinal fluid, intraretinal fluid, hypertransmission, descent of the outer plexiform layer, and pigment epithelium detachment showed highest interreader agreement, while detection and measures of loss of ellipsoid zone and retinal pigment epithelium were more variable. The agreement on the size and location of the respective annotation was more consistent throughout all features.

Conclusions

The interreader agreement depended on the respective OCT-based feature. A selection of reliable features might provide suitable surrogate markers for disease progression and possible treatment effects focusing on different disease stages.

Translational Relevance

This might give opportunities for a more time- and cost-effective patient assessment and improved decision making as well as have implications for clinical trials and training machine learning algorithms.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Assessment of Diabetic Retinopathy Vascular Density Maps

Purpose

Optical coherence tomography (OCT) and OCTA were used for qualitative and quantitative assessment of retinal vascular density in superficial capillary plexus, deep capillary plexus, foveal avascular zone, and choroidal vascular density map.

Patients and Methods

This study included 64 eyes. Diabetics and control groups were recruited from an internal medicine clinic at Misr University for Science and Technology Hospital and asked to participate in this study. This study was designed as an observational and cross-sectional study in the period from 8/2018 to 8/2019.

Results

There was a decrease in choroidal vascular density in diabetic patients. There was a decrease in retinal thickness in diabetic patients and there were no significant differences in the retinal thickness between control subjects and patients with non-diabetic retinopathy (NDR).

Conclusion

Our study suggests that OCTA can identify preclinical DR before the manifestation of clinically apparent retinopathy. Our findings also highlight the potential role of OCTA in monitoring and quantifying retinal vascular alterations in diabetics.

Enhanced depth imaging in swept-source optical coherence tomography: Improving visibility of choroid and sclera, a masked study

Purpose

To compare enhanced depth imaging in swept-source optical coherence tomography and non–enhanced depth imaging optical coherence tomography in their ability to capture choroidal and scleral details.

Methods

Averaged foveal B-Scans were obtained from 40 eyes of 20 healthy volunteers by swept-source optical coherence tomography with and without enhanced depth imaging. Visibility and contrast of vascular details within the choroid, choroidoscleral junction, and sclera were evaluated by masked readers using an ordinal scoring scale. Outcomes were analyzed using the Wilcoxon signed rank-sum test.

Results

Visibility of the choroidal vascular details ( Z = 5.94, p < .001), the choroidoscleral junction ( Z = 5.85, p < .001), and the sclera ( Z = 6.80, p < .001) was significantly higher with enhanced depth imaging than with non–enhanced depth imaging swept-source optical coherence tomography. Similarly, image contrast was significantly higher with enhanced depth imaging than with non–enhanced depth imaging swept-source optical coherence tomography for the choroidal vascular details ( Z = 9.47, p < .001), for the choroidoscleral junction ( Z = 9.28, p < .001), and for the sclera ( Z = 9.42, p < .001).

Conclusion

Enhanced depth imaging applied to swept-source optical coherence tomography–averaged foveal B-scans enhances visualization of the choroidal details, of the choroidoscleral junction, and of the sclera. This novel modality can easily be implemented in clinics and could improve our understanding of conditions involving the choroid or the sclera.

Optical Coherence Tomography: Critical Tool to Manage Expectations after Cataract Extraction

Purpose of Review

To review evidence on the utility of spectral domain optical coherence tomography (SD-OCT) in evaluating retinal structure prior cataract surgery and highlight new technologies that can assess retinal function perioperatively.

Findings

SD-OCT detected clinically unsuspected macular pathology in 4.6-25% of individuals in the pre-operative cataract evaluation. The most common findings were epiretinal membrane and macular degeneration with frequencies that varied by population studied. These conditions have been associated with complication after surgery (e.g. macular edema, visual dissatisfaction). As such, findings on SD-OCT may impact the informed consent process, alter IOL selection, and provide realistic postoperative vision expectations. Other technologies that assess retinal function, such as microperimetry and multifocal ERG are beginning to be studied but their utility in the pre-operative cataract evaluation is not yet known.

Summary

SD-OCT should be incorporated as a routine test prior to surgery to manage patient expectations and assist with optimal IOL selection, as even individuals with a seemingly normal clinical exam may have macular pathology. SD-OCT is the most established method for evaluating retinal anatomy and offers the benefits of a reduction in cases with missed macular pathology and fewer postoperative visual surprises.

Accuracy of a deep convolutional neural network in the detection of myopic macular diseases using swept-source optical coherence tomography

This study examined and compared outcomes of deep learning (DL) in identifying swept-source optical coherence tomography (OCT) images without myopic macular lesions [i.e., no high myopia (nHM) vs. high myopia (HM)], and OCT images with myopic macular lesions [e.g., myopic choroidal neovascularization (mCNV) and retinoschisis (RS)]. A total of 910 SS-OCT images were included in the study as follows and analyzed by k-fold cross-validation (k = 5) using DL's renowned model, Visual Geometry Group-16: nHM, 146 images; HM, 531 images; mCNV, 122 images; and RS, 111 images (n = 910). The binary classification of OCT images with or without myopic macular lesions; the binary classification of HM images and images with myopic macular lesions (i.e., mCNV and RS images); and the ternary classification of HM, mCNV, and RS images were examined. Additionally, sensitivity, specificity, and the area under the curve (AUC) for the binary classifications as well as the correct answer rate for ternary classification were examined. The classification results of OCT images with or without myopic macular lesions were as follows: AUC, 0.970; sensitivity, 90.6%; specificity, 94.2%. The classification results of HM images and images with myopic macular lesions were as follows: AUC, 1.000; sensitivity, 100.0%; specificity, 100.0%. The correct answer rate in the ternary classification of HM images, mCNV images, and RS images were as follows: HM images, 96.5%; mCNV images, 77.9%; and RS, 67.6% with mean, 88.9%.Using noninvasive, easy-to-obtain swept-source OCT images, the DL model was able to classify OCT images without myopic macular lesions and OCT images with myopic macular lesions such as mCNV and RS with high accuracy. The study results suggest the possibility of conducting highly accurate screening of ocular diseases using artificial intelligence, which may improve the prevention of blindness and reduce workloads for ophthalmologists.

Myopia and Regional Variations in Retinal Thickness in Healthy Eyes

Purpose

To investigate the effects of refraction on retinal thickness measurements at different locations and layers in healthy eyes of Saudi participants.

Methods

Thirty-six randomly selected adults aged 27.0 ± 5.7 years who attended a Riyadh hospital from 2016 to 2017 were categorized into three groups: non-myopic (spherical equivalent refraction [SER], +1.00 to –0.50 diopters [D]), low myopic (SER, –0.75 to –3.00D), and moderate to high myopic (SER ≤ –3.25D). Full, inner, and outer retinal thicknesses were measured at nine locations by spectral-domain stratus optical coherence tomography (Optovue Inc., Fremont, CA, USA) and were compared according to refractive group and sex.

Results

The mean SERs for the non-myopia, low myopia, and moderate to high myopia groups were 0.2 ± 0.6, –1.5 ± 0.5, and –7.5 ± 1.9 D, respectively. Refractive error, but not sex, had significant effects on the retinal layer thickness measurements at different locations (P < 0.05). The parafoveal and outer retinal layers were significantly thicker than the perifoveal and inner retina layers in all groups (P < 0.05). The full foveal thickness was higher and the full parafoveal and perifoveal regions were thinner in moderate to high myopic eyes than in the non-myopic eyes (P < 0.05), but were similar to those in the low myopic eyes (P > 0.05). The foveal thicknesses measured in the inner and outer layers of the retina were higher but the thicknesses measured at the inner and outer layers of the parafoveal and perifoveal regions were lower in moderate to high myopic eyes.

Conclusion

There were regional differences in the retinal layer thicknesses of healthy Saudi eyes, which was dependent on the central refractions. This is important when interpreting retinal nerve fiber layer thicknesses in myopia and disease management in Saudi participants.

Comparison of retinal layer thickness measurements obtained using two different swept-source optical coherence tomography imaging modes

PURPOSE

To compare the retinal layer thickness values obtained using two swept-source optical coherence tomography (OCT) wide modes.

METHODS

This study included fifty-four healthy eyes. Three-dimensional (3D) wide and 12 radial wide OCT scans were performed in each eye on the same day. Full retinal, retinal nerve fiber layer (RNFL), and ganglion cell-inner plexiform layer (GC-IPL) thicknesses with fully automated segmentation obtained in 3D wide mode, and with semi-automated correction and fully automated segmentation obtained in 12 radial wide scan.

RESULTS

The intraclass correlation coefficients for full retinal thickness measurements obtained by the two protocols with fully automated segmentation were from 0.958 to 0.996, 0.754-0.918 for GC-IPL thickness measurements, and 0.013-0.727 for RNFL thickness measurements, in the nine ETDRS subfields.

CONCLUSIONS

The full retinal thickness measurements determined using both fully automated segmentation algorithms were reliable and clinically acceptable. However, segmentation errors are shown when using the 12 radial wide scanning protocol with fully automated segmentation for measurement of RNFL and GC-IPL thickness.

[Swept source optical coherence tomography: a technology review]

The article reviews the concept of swept source optical coherence tomography (SS-OCT) and presents a brief history of the technology, its implementation in modern commercial tomography, the advantages and disadvantages of the method.

Intravitreal Ziv-Aflibercept : Safety Analysis in Eyes Receiving More Than Ten Intravitreal Injections

Purpose: To report the ocular and systemic adverse events in eyes receiving ≥10 intravitreal ziv-aflibercept (IVZ) injections.Methods: Medical records of patients who received ≥10 IVZ for various chorioretinal conditions with minimum follow up period of 12 months were retrospectively analysed. These eyes received standard dose of IVZ (1.25 mg/0.05 ml) on pro-re-nata (PRN) or treat and extend (T&E) protocol. The primary study outcome was ocular and systemic adverse events related to IVZ injections whereas secondary outcomes were change in best corrected visual acuity (BCVA) and central macular thickness (CMT) on optical coherence tomography (OCT) at last visit compared to baseline. Comparison of BCVA and CMT at baseline and final visit was done using paired t-test.Results: A total of 94 eyes which received a mean ± standard deviation (mean±SD = 14.4 ± 4.6) IVZ injections were studied. A total of 41 eyes were treatment naïve whereas 53 eyes received intravitreal injections in the past with last injection at least 3 months prior. Mean (±SD) follow up period was 26.7 ± 8.7 months. Ocular adverse events were limited with a case each of acute iridocyclitis, endophthalmitis, cataract progression and early epiretinal membrane formation. No systemic events were recorded within a month of IVZ injection. There was a significant improvement in BCVA (p = 0.001) and change in CMT (p = 0.001) at last visit.Conclusion: Ocular use of ziv-aflibercept is safe with limited ocular and systemic side effects. Multiple injections of IVZ can be used in various chorioretinal diseases over the long term.

Retinal Layer Thicknesses in Early Age-Related Macular Degeneration: Results From the German AugUR Study

Purpose

To systematically analyze thicknesses of retinal layers in an older population and their link to early age-related macular degeneration (AMD).

Methods

In the AugUR baseline survey from a population aged ≥70 years, we conducted multimodal retinal imaging, including spectral-domain optical coherence tomography. Autosegmentation of eight distinct retinal layers was followed by manual correction of segmentation errors. AMD status was graded on color fundus images according to the Three Continent AMD Consortium Severity Scale. We tested the association of early AMD on retinal layer thicknesses by using linear mixed models and replicated significant results in independent data also from the AugUR platform.

Results

When comparing layer thicknesses between early AMD and no AMD (822 eyes, 449 participants), the retinal pigment epithelium/Bruch's membrane complex demonstrated a statistically significant thickening (e.g., P = 6.41 × 10⁻⁹² for severe early versus no AMD) and photoreceptor layers showed a significant thinning. Autosegmented retinal layer thicknesses revealed similar associations as manually corrected values but underestimated some effects. Independent replication analysis in 1026 eyes (546 participants) confirmed associations (e.g., P = 9.38 × 10⁻³⁶ for retinal pigment epithelium/Bruch's membrane complex, severe early versus no AMD).

Conclusions

This first population-based study on spectral-domain optical coherence tomography-derived retinal layer thicknesses in a total of ∼1000 individuals provides insights into the reliability of autosegmentation and layer-specific reference values for an older population. Our findings show a difference in thicknesses between early AMD and no AMD for some retinal layers, suggesting these as potential imaging biomarkers. The thinning of photoreceptor layers substantiates a photoreceptor cell loss/damage already occurring in early AMD.

Quantum mechanism of light energy propagation through an avian retina

Taking into account the ultrastructure of the Pied Flycatcher foveal retina reported earlier and the earlier reported properties of Müller cell (MC) intermediate filaments (IFs) isolated from vertebrate retina, we proposed a quantum mechanism (QM) of light energy transfer from the inner limiting membrane level to visual pigments in the photoreceptor cells. This mechanism involves electronic excitation energy transfer in a donor-acceptor system, with the IFs excited by photons acting as energy donors, and visual pigments in the photoreceptor cells acting as energy acceptors. It was shown earlier that IFs with diameter 10 nm and length 117 μm isolated from vertebrate eye retina demonstrate properties of light energy guide, where exciton propagates along such IFs from MC endfeet area to photoreceptor cell area. The energy is mostly transferred via the contact exchange quantum mechanism. Our estimates demonstrate that energy transfer efficiencies in such systems may exceed 80-90%. Thus, the presently developed quantum mechanism of light energy transfer in the inverted retina complements the generally accepted classic optical mechanism and the mechanism whereby Müller cells transmit light like optical fibers. The proposed QM of light energy transfer in the inverted retina explains the high image contrast achieved in photopic conditions by an avian eye, being probably also active in other vertebrates.

Comparison of repeatability of swept-source and spectral-domain optical coherence tomography for measuring inner retinal thickness in retinal disease

Purpose

To compare repeatability between SS-OCT and SD-OCT for measurement of macular, macular retinal nerve fiber (mRNFL), and ganglion cell-inner plexiform layer (GC-IPL) thickness in various retinal diseases.

Methods

One hundred and fourteen eyes of 114 subjects were investigated. Seventy-eight eyes with retinal disease and 36 normal eyes underwent two consecutive measurements of macular, mRNFL, and GC-IPL thickness using SS-OCT and SD-OCT. The data were obtained using the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. The eyes with retinal diseases were divided into three subgroups according to central macular thickness (CMT) for analysis. The intraclass correlation coefficient (ICC) was calculated to determine the repeatability of OCT device.

Results

In normal eyes, both OCT devices showed excellent repeatability of macula, mRNFL, and GC-IPL thickness measurements with high ICCs in all ETDRS subfields. In eyes with retinal disease, although SS-OCT showed better repeatability for inner retinal thickness measurements than SD-OCT, the overall ICCs were lower than those in normal eyes. In subgroup analysis, the ICCs in the low CMT group were lower than those in the normal and high CMT groups, particularly when using SD-OCT.

Conclusions

Both OCT devices had comparable repeatability for retinal thickness measurement in normal eyes and eyes with retinal disease. However, the possibility of measurement error should be considered in eyes with a thin and atrophic retina.

Factors affecting foveal avascular zone in healthy eyes: An examination using swept-source optical coherence tomography angiography

OBJECTIVE

To examine factors affecting foveal avascular zone (FAZ) area in healthy eyes using swept-source optical coherence tomography angiography (OCTA).

METHODS

This prospective, cross-sectional study included 144 eyes of 144 individuals (77 women, 67 men) with a best corrected visual acuity of at least 20/20 and no history of ocular disorders. The area of the superficial FAZ was assessed using OCTA. Age, gender, central retinal thickness (CRT), retinal vascular density, refractive error, and axial length were examined to determine associations with FAZ area.

RESULTS

The mean age of the subjects was 42.1 ± 20.2 years (range: 10-79 years). The mean FAZ area was 0.32 ± 0.11 mm2, while the mean retinal vascular density was 35.53 ± 0.92%. Multivariate regression analysis was performed using FAZ area as the dependent variable and age, gender, CRT, retinal vascular density, refractive error, and axial length as independent variables. The results of this analysis demonstrate that CRT and retinal vascular density were significantly associated with FAZ area in our sample (P < 0.001, R2 = 0.425). Age, gender, refractive error, and axial length were not significantly correlated with FAZ area, while CRT and retinal vascular density were negatively correlated with FAZ area (CRT: P < 0.001, R2 = 0.356; retinal vascular density: P < 0.001, R2 = 0.189).

CONCLUSIONS

OCTA results suggest that CRT and retinal vascular density negatively affect FAZ area in healthy eyes.

Assessment of Vascular Change Using Swept-Source Optical Coherence Tomography Angiography: A New Theory Explains Central Visual Loss in Behcet's Disease

OBJECTIVE

To evaluate retinal vascular structural change in ocular Behcet's using optical coherence tomography angiography (OCTA) and fluorescein angiography (FA).

METHODS

An analytic cross-sectional study of 37 eyes of 21 Behcet's uveitic patients was performed. Foveal retinal thickness (FRT), perifoveal hypoperfusion areas in superficial capillary plexus (SCP), and deep capillary plexus (DCP) were measured with swept-source optical coherence tomography and OCTA. FA images were used for assessing the vascular features and correlation.

RESULTS

Twenty-one patients were enrolled (52.4% males). The average age at onset was 36.7 ± 12.93 years. The median of disease duration was 5 years (1-25). FRT was 118.1 ± 52.35 μm, which correlated with visual acuity (95% CI -60.47, -13.92). Using OCTA, the area of hypoperfusion in SCP (0.47 ± 0.17 mm²) was smaller than that in DCP (1.94 ± 3.87 mm²) (p < 0.001). Superficial to deep capillary plexus nonperfusion (SCP : DCP) ratio was 0.57 ± 0.27 which had the positive coefficient correlation with visual acuity (95% CI -0.644, -0.015).

CONCLUSIONS

OCTA is an alternative noninvasive method to monitor macular ischemia in Behcet. Behcet's uveitis affects DCP more than SCP. Decreasing SCP : DCP ratio and decrease FRT correlates with poor visual acuity. Macular ischemia and DCP loss can be found early and can explain vision loss in Behcet.

Influence of Retinal Pathology on the Reliability of Macular Thickness Measurement: A Comparison Between Optical Coherence Tomography Devices

BACKGROUND AND OBJECTIVE

To evaluate the repeatability, reliability, and comparability of macular thickness measurements between three optical coherence tomography (OCT) machines in healthy eyes, eyes with diabetic macular edema (DME), and eyes with neovascular age-related macular degeneration (nAMD).

PATIENTS AND METHODS

Twenty-three eyes with DME, 26 eyes with nAMD, and 24 healthy eyes as controls were evaluated. Scans were performed using the swept-source Triton (Topcon, Tokyo, Japan), the spectral-domain Cirrus (Carl Zeiss Meditec, Dublin, CA), and the Spectralis (Heidelberg Engineering, Heidelberg, Germany) machines. Scans were evaluated for central macular thickness (CMT), presence of segmentation and fixation imaging artifacts (IA), re-scan reliability, and agreement between machines and groups.

RESULTS

Mean CMT was significantly different between all OCT machines in all groups (P < .01 for all comparisons). Manually correcting IA did not alter these results. There was good scan repeatability among healthy and DME eyes for each machine, but poor repeatability among the nAMD group with the Spectralis (P = .038). IA were significantly increased in the presence of pathology.

CONCLUSIONS

There is poor agreement of CMT measurement between OCT machines in healthy eyes and those with DME and nAMD. DME and nAMD have a significant effect on the rate of IA in scans. Care is required when interpreting measurements from different OCT devices in clinical practice and research settings. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:319-325.].

Macular thickness in healthy eyes of adults (N = 4508) and relation to sex, age and refraction: the Tromsø Eye Study (2007-2008)

Purpose

To provide sex‐stratified normative data on retinal thickness and study the relationship with sex, age and refractive status.

Methods

Population‐based study including 2617 women and 1891 men, aged 38–87 (mean 61 ± 8) years, without diabetes, glaucoma and retinal diseases, and spherical equivalent refraction (SER) within ±6 dioptres. Retinal thickness was measured with optical coherence tomography (spectral domain Cirrus HD‐OCT).

Results

Women had thinner retina than men. Retinal thickness was significantly associated with refraction, where mean change in retinal thickness per 1 D increase in SER was −1.3 (0.2) μm in the fovea, 0.7 (0.1) μm in the pericentral ring and 1.4 (0.1) μm in the peripheral ring. In the fovea, there was a non‐monotonic curved relationship between retinal thickness and age in both sexes with a maximum at about 60 years (p < 0.001). In the pericentral ring, the mean reduction in retinal thickness per 10‐year increase was 2.7 (0.3) μm in women and 4.0 (0.4) μm in men and corresponding results in the peripheral ring were 2.3 (0.3) μm in women and 2.6 (0.4) μm in men. In both regions, there was evidence for a nonlinear pattern with an increased rate of change with higher age. There was a significant interaction between sex and age for retinal thickness of the pericentral ring (p = 0.041).

Conclusion

Women had thinner retina than men, and thickness varied with refractive status. Retinal thickness was associated with age in all macular regions, and the rate of change in retinal thickness varied at different ages.

Relationship between Myopia Severity and Macular Retinal Thickness on Visual Performance under Different Lighting Conditions

OBJECTIVE

To evaluate the relationship between both spherical equivalent (SE) and retinal thickness (RT) on best-corrected visual acuity (BCVA) among young Asian adult men under photopic, mesopic, and simulated night-vision goggle (NVG) lighting conditions.

DESIGN

Community-based cross-sectional study.

PARTICIPANTS

Total of 698 myopic and 148 emmetropic subjects.

METHODS

All participants underwent a complete ophthalmic examination and color fundus photography. BCVA and subjective refraction were assessed under standardized photopic, mesopic, and simulated NVG lighting conditions. Retinal thickness in various Early Treatment Diabetic Retinopathy Study (ETDRS) subfields was measured using spectral-domain OCT using a standardized protocol. Univariate and multiple linear regression analyses were performed to assess the relationship between BCVA and both SE and RT.

MAIN OUTCOME MEASURES

Relationship between BCVA and both SE and RT.

RESULTS

The mean age of all subjects was 21.1 years, with mean SE of -8.44 diopter (D) among the myopic subjects (range, -3.75 D to -23.0 D) and +0.10 among the emmetropic subjects (range, -0.49 D to +1.00 D). BCVA worsened progressively with increasing myopia under all lighting conditions (standardized coefficient -0.581 under photopic conditions, P < 0.001). RT was thickest among participants with LogMAR VA ≤0.00, and became thinner in the groups including those with VA >0.00 to ≤0.10 and >0.10 (mean inner subfield RT: 342.7 μm vs. 338.1 μm vs. 331.0 μm, respectively, P < 0.001) under all lighting conditions. When multiple linear regression was performed, higher degrees of myopia and decreasing RT were associated with reduced BCVA (all P < 0.05). For each diopter increase in myopia, mean BCVA decreased by 0.01 LogMAR in photopic conditions and 0.02 LogMAR in mesopic conditions (both P < 0.001). The mean BCVA reduced by 0.05 LogMAR (P = 0.003) and 0.04 LogMAR (P = 0.037), under photopic and scotopic lighting conditions respectively, for each 100-μm decrease in RT.

CONCLUSIONS

Both the severity of myopia and macular RT independently affect visual performance under photopic, mesopic, and simulated NVG conditions.

Comparison of macular choroidal thicknesses from swept source and spectral domain optical coherence tomography

BACKGROUND

Choroidal thickness (CT) measurements differ between swept source optical coherence tomography (SS-OCT) and spectral domain OCT (SD-OCT) devices for point thickness measurements. We aimed to assess the comparability of mean macular CT measurements between SS-OCT and SD-OCT devices.

METHODS

In a prospective cohort study of 25 healthy volunteers, OCT scans were performed sequentially with the deep range imaging (DRI) OCT-1 and Spectralis OCT using standardised imaging protocols. These OCT scans were independently graded by reading centre-certified graders to obtain mean CT in the various Early Treatment Diabetic Retinopathy Study (ETDRS) subfields. Paired t tests and intraclass correlation coefficients (ICCs) were used to compare the measurements.

RESULTS

The difference in mean central subfield CT between DRI OCT-1 and Spectralis was 49.3 µm (p<0.001), while differences in CT in various ETDRS subfields varied from 42.1 to 67.2 µm. After manual adjustment of the segmentation boundaries for the central subfield in the DRI OCT-1, the mean central subfield CT for DRI OCT-1 increased from 263.1 to 293.3 µm (p<0.001), and the resultant difference between DRI OCT-1 and Spectralis decreased from 49.3 to 19.1 µm (a decrease of 61.3%; p<0.001). CT between the three-dimensional and radial scanning protocols of the DRI OCT-1 were highly comparable, with differences generally under 10 µm and ICC of 0.888 for the central subfield.

CONCLUSIONS

CT measurements between automated segmentations from the DRI OCT-1 and manual segmentations on the Spectralis OCT may differ by more than 50 µm. This difference can be reduced, but not eliminated, by manual adjustment of segmentation boundaries by trained graders, and should be accounted for when comparing results between the two devices.