The Optical Coherence Tomography and Microperimetry Biomarker Evaluation in Patients with Geographic Atrophy (OMEGA) Study: Design and Baseline Characteristics - OMEGA Report 1.

INTRODUCTION: The aim of this study was to describe the design and the participants' baseline characteristics of a prospective natural history study of geographic atrophy (GA) secondary to age-related macular degeneration. METHODS: The optical coherence tomography (OCT) and microperimetry biomarker evaluation in patients with GA (OMEGA) study was conducted at a tertiary referral center (ClinicalTrials.gov identifier: NCT05963646). Participants were followed for 12 months during 4 visits (baseline and follow-up exams at weeks 12, 24, and 48) with best-corrected Early Treatment of Diabetic Retinopathy Study visual acuity, low-luminance visual acuity (LLVA), and quick contrast sensitivity function testing. Further, participants underwent spectral-domain OCT, OCT angiography, fundus autofluorescence imaging, and mesopic microperimetry testing. RESULTS: Thirty participants (median [IQR] age of 79 [77, 84] years) and 37 study eyes were included with a (median [IQR]) GA area of 1.40 mm2 (0.49, 5.24) at baseline. Out of 37 study eyes, six developed macular neovascularizations (16%). The study-eye best-corrected visual acuity was (median [IQR]) 0.18 logarithm of the minimum angle of resolution (logMAR) (0.06, 0.26), LLVA 0.66 logMAR (0.36, 0.88), and the microperimetry mean sensitivity 18.4 dB (9.21, 20.9). The highest correlation between square root GA area and a visual function test was evident for LLVA (R2 of 0.578), followed by area under the log contrast sensitivity function curve (0.519) and microperimetral retinal sensitivity (0.487). CONCLUSION: This report lays out the design and baseline characteristics of the OMEGA study, which aims to contribute to the understanding of the natural history of GA. The OMEGA study will provide estimates of the ability to detect change and retest reliability for a panel of structure and functional assessments.

Genotype-Phenotype Association in ABCA4-Associated Retinopathy.

Stargardt disease (STGD1) is the most common inherited retina degeneration. It is caused by biallelic ABCA4 variants, and no treatment is available to date. STGD1 shows marked phenotypic variability, especially regarding the age of onset. The underlying genotype can partially explain this variability. Notably, a subset of ABCA4 variants was previously associated with an earlier disease onset than truncating ABCA4 variants, pointing toward pathogenic mechanisms beyond the loss of gene function in these patients. On the other end of the spectrum, variants such as p.Gly1961Glu were associated with markedly slower extrafoveal disease progression. Given that these drastic differences in phenotype are based on genotype (resulting in important prognostic implications for patients), this chapter reviews previous approaches to genotype-phenotype correlation analyses in STGD1.

Choriocapillaris Flow Signal Impairment in Sorsby Fundus Dystrophy.

PURPOSE: The aim of the study was to quantify choriocapillaris (CC) flow alterations in early Sorsby fundus dystrophy (SFD) and to investigate the relationship of the CC flow deficits with the choroidal and outer retinal microstructure. METHODS: In this prospective case-control study, 18 eyes of 11 patients with early SFD and 31 eyes of 31 controls without ocular pathology underwent multimodal imaging, including spectral-domain optical coherence tomography (OCT), followed by deep-learning-based layer segmentation. OCT angiography (OCTA) was performed to quantify CC flow signal deficits (FDs). Differences in CC FD density between SFD patients and controls were determined, and the relationships with choroidal thickness, retinal pigment epithelium-drusen complex (RPEDC) thickness and outer retinal layer thicknesses were analyzed using mixed-model analysis. RESULTS: SFD patients exhibited a significantly greater CC FD density than controls (estimate [95% CI]: +20.0%FD [13.3; 26.7], p < 0.001 for SFD patients), even when adjusted for age. Square-root transformed choroidal thickness was a structural OCT surrogate of the CC FD density (-2.1%FD per √µm, p < 0.001), whereas RPEDC thickness was not informative regarding CC FD (p = 0.061). The CC FD density was associated with an altered microstructure of the overlying photoreceptors (outer segments, inner segments, and outer nuclear layer thinning of -0.19 µm, -0.08 µm and -0.30 µm per %FD, respectively, all p < 0.001). CONCLUSIONS: Patients with early SFD exhibit pronounced abnormalities of CC flow signal on OCTA, which are not limited to areas of sub-RPE deposits seen on OCT imaging. Thus, analysis of the CC flow may enable clinical trials at earlier disease stages in SFD.

Modeling of atrophy size trajectories: variable transformation, prediction and age-of-onset estimation.

BACKGROUND: To model the progression of geographic atrophy (GA) in patients with age-related macular degeneration (AMD) by building a suitable statistical regression model for GA size measurements obtained from fundus autofluorescence imaging. METHODS: Based on theoretical considerations, we develop a linear mixed-effects model for GA size progression that incorporates covariable-dependent enlargement rates as well as correlations between longitudinally collected GA size measurements. To capture nonlinear progression in a flexible way, we systematically assess Box-Cox transformations with different transformation parameters λ. Model evaluation is performed on data collected for two longitudinal, prospective multi-center cohort studies on GA size progression. RESULTS: A transformation parameter of λ=0.45 yielded the best model fit regarding the Akaike information criterion (AIC). When hypertension and hypercholesterolemia were included as risk factors in the model, they showed an association with progression of GA size. The mean estimated age-of-onset in this model was 67.21±6.49 years. CONCLUSIONS: We provide a comprehensive framework for modeling the course of uni- or bilateral GA size progression in longitudinal observational studies. Specifically, the model allows for age-of-onset estimation, identification of risk factors and prediction of future GA size. A square-root transformation of atrophy size is recommended before model fitting.

NATURAL HISTORY OF QUANTITATIVE AUTOFLUORESCENCE IN INTERMEDIATE AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To investigate differences in quantitative autofluorescence (qAF) imaging measurements between eyes with and without large drusen, and whether qAF measurements change over time in the eyes with large drusen. METHODS: Eighty-five eyes from participants with bilateral large drusen and 51 eyes from healthy participants underwent qAF imaging at least once, and the age-related macular degeneration participants were reviewed 6-monthly. Normalized grey values at 9° to 11° eccentricity from the fovea were averaged to provide a summary measure of qAF values (termed qAF8). RESULTS: In a multivariable model, qAF8 measurements were not significantly different between age-related macular degeneration eyes with large drusen and healthy eyes (P = 0.130), and qAF8 measurements showed a decline over time in the age-related macular degeneration eyes (P = 0.013). CONCLUSION: These findings add to the body of evidence that qAF levels are not increased in eyes with large drusen compared with healthy eyes, and qAF levels show a significant decline over time in the age-related macular degeneration eyes. These findings highlight how the relationship between qAF levels and retinal pigment epithelium health does not seem to be straightforward. Further investigation is required to better understand this relationship, especially if qAF levels are to be used as an outcome measure in intervention trials.

Optical Coherence Tomography-Angiography in Geographic Atrophy.

Geographic atrophy (GA) represents the non-exudative late stage of age-related macular degeneration and constitutes a leading cause of legal blindness in the developed world. It is characterized by areas of loss of outer retinal layers including photoreceptors, degeneration of the retinal pigment epithelium, and rarefication of the choriocapillaris. As all three layers are functionally connected, the precise temporal sequence and relative contribution of these layers towards the development and progression of GA is unclear. The advent of optical coherence tomography angiography (OCT-A) has allowed for three-dimensional visualization of retinal blood flow. Using OCT-A, recent studies have demonstrated that choriocapillaris flow alterations are particularly associated with the development of GA, exceed atrophy boundaries spatially, and are a prognostic factor for future GA progression. Furthermore, OCT-A may be helpful to differentiate GA from mimicking diseases. Evidence for a potential protective effect of specific forms of choroidal neovascularization in the context of GA has been reported. This article aims to give a comprehensive review of the current literature concerning the application of OCT-A in GA, and summarizes the opportunities and limitations with regard to pathophysiologic considerations, differential diagnosis, study design, and patient assessment.

The Willingness of Patients to Participate in an Eye Donation Registry for Research.

INTRODUCTION: For ophthalmologic research, the systematic correlation of clinical data with data obtained from postmortem tissue donation is of great benefit. In this respect, the establishment of an eye donation registry represents a prerequisite for the acquisition of such data. METHODS: A total of 300 patients were interviewed at a tertiary referral center in Germany by means of a standardized questionnaire. Binary questions were evaluated by percentage; Likert-scaled questions (1 = does apply; 5 = does not apply) were analyzed by the median and 25th (Q25) and 75th (Q75) percentiles. RESULTS: The majority of patients (77.0%) would agree to donate their eyes for research purposes. When asked about reasons against an eye donation, 60.9% of all patients only stated reasons in the category "addressable" (e.g., not enough awareness of the topic). The vast majority of patients considered it appropriate for an ophthalmologist to approach them on the issue of postmortem eye donation (median 1, Q25 1, Q75 1). CONCLUSION: Overall, patients had a positive attitude towards postmortem eye donation for research purposes. Importantly, reasons given against postmortem eye donation were often related to misconceptions and were potentially addressable. These results underline the fundamental willingness of ophthalmological patients in Germany to donate their eyes postmortem for research purposes.

PROGRESSION OF ABCA4-RELATED RETINOPATHY: Prognostic value of demographic, functional, genetic, and imaging parameters.

PURPOSE: To investigate the prognostic value of demographic, functional, genetic, and imaging parameters on retinal pigment epithelium atrophy progression secondary to ABCA4-related retinopathy. METHODS: Patients with retinal pigment epithelium atrophy secondary to ABCA4-related retinopathy were examined longitudinally with fundus autofluorescence imaging. Lesion area, perimeter, circularity, caliper diameters, and focality of areas with definitely decreased autofluorescence were determined. A model was used to predict the lesion enlargement rate based on baseline variables. Sample size calculations were performed to model the power in a simulated interventional study. RESULTS: Sixty-eight eyes of 37 patients (age range, 14-78 years) with a follow-up time of 10 to 100 months were included. The mean annual progression of retinal pigment epithelium atrophy was 0.89 mm. The number of atrophic areas, the retina-wide functional impairment, and the age-of-onset category constituted significant predictors for future retinal pigment epithelium atrophy growth, explaining 25.7% of the variability. By extension of a simulated study length and/or specific patient preselection based on these baseline characteristics, the required sample size could significantly be reduced. CONCLUSION: Trial design based on specific shape-descriptive factors and patients' baseline characteristics and the adaption of the trial duration may provide potential benefits in required cohort size and absolute number of visits.

MESOPIC AND DARK-ADAPTED TWO-COLOR FUNDUS-CONTROLLED PERIMETRY IN GEOGRAPHIC ATROPHY SECONDARY TO AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To investigate retinal sensitivity in the junctional zone of geographic atrophy (GA) secondary to age-related macular degeneration using patient-tailored perimetry grids for mesopic and dark-adapted two-color fundus-controlled perimetry. METHODS: Twenty-five eyes with GA of 25 patients (prospective, natural-history Directional Spread in Geographic Atrophy study [DSGA; NCT02051998]) and 40 eyes of 40 normal subjects were included. Patient-tailored perimetry grids were generated using annotated fundus autofluorescence data. Customized software positioned test-points along iso-hulls surrounding the GA boundary at distances of 0.43°, 0.86°, 1.29°, 2.15°, and 3.01°. The grids were used for duplicate mesopic and dark-adapted two-color (cyan and red) fundus-controlled perimetry. Age-adjusted reference-data were obtained through regression analysis of normative data followed by spatial interpolation. RESULTS: The mean sensitivity loss for mesopic testing decreased with the distance to GA (-10.3 dB [0.43°], -8.2 dB [0.86°], -7.1 dB [1.29°], -6.8 dB [2.15°], and -6.6 dB [3.01°]; P < 0.01). Dark-adapted cyan sensitivity loss exceeded dark-adapted red sensitivity loss for all iso-hulls (-14.8 vs. -11.7 dB, -13.5 vs. -10.1 dB, -12.8 vs. -9.1 dB, -11.6 vs. -8.2 dB, -10.7 vs. -8.0 dB; P < 0.01). CONCLUSION: Patient-tailored fundus-controlled perimetry grids allowed for testing of retinal function in the junctional zone of GA with high spatial resolution. A distinct decrease in mesopic sensitivity loss between 0.43° (125 µm) and 1.29° (375 µm) was observed that leveled off at more distant test-points. In proximity to the GA boundary, the results indicate that rod exceeded cone dysfunction.

Assessment of Exudative Activity of Choroidal Neovascularization in Age-Related Macular Degeneration by OCT Angiography.

PURPOSE: Based on exudative activity, choroidal neovascularization (CNV) in age-related macular degeneration (AMD) can be classified as "active" aCNV, pretherapied "silent" sCNV (i.e., a treatment-free interval >12 weeks), or treatment-naïve "quiescent" qCNV. We evaluated the qualitative and quantitative optical coherence tomography angiography (OCTA) features of these CNV subgroups. METHODS: The presence of small-caliber vessels, peripheral arcades, and a -perilesional OCTA signal attenuation as well as values for vessel length, density, and branching index were evaluated for each CNV network in a 6 × 6 mm OCTA scan pattern. RESULTS: Fifty-one eyes of 51 patients with AMD (age 75.9 ± 7.5 years; 20 males [39.2%]) were included. The qCNV subgroup (n = 8) showed the highest prevalence of qualitative and quantitative values for OCTA activity criteria, reaching significance with regard to small-caliber vessels (p = 0.003), peripheral arcades (p = 0.039), vessel length (p = 0.020), and branching index (p < 0.001) when compared to the aCNV (n = 32) and sCNV (n = 11) subgroups. Qualitative criteria were inversely associated with the number of previous anti-VEGF injections (each p < 0.03), while quantitative metrics also suggested lower values. CONCLUSIONS: These findings suggest that OCTA may be supportive in the phenotypical differentiation of CNV lesions secondary to AMD, while the assessed structural changes appeared to be more indicative of previously administered anti-VEGF therapy than current exudative activity.

PROGNOSTIC VALUE OF SHAPE-DESCRIPTIVE FACTORS FOR THE PROGRESSION OF GEOGRAPHIC ATROPHY SECONDARY TO AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To systematically compare the prognostic value of multiple shape-descriptive factors in the natural course of the disease. METHODS: A total of 296 eyes of 201 patients (female patients 130; mean age: 72.2 ± 13.08 years) with a median follow-up of 2.38 years from 2 prospective, noninterventional natural history studies (Fundus-Autofluorescence-in-Age-related-Macular-Degeneration [clinicaltrials.gov identifier NCT00393692], Directional-Spread-in-Geographic-Atrophy [NCT02051998]) were included in the analysis. Serial fundus autofluorescence images were annotated using semiautomated image analysis software to determine the lesion area, circularity, perimeter, and caliper diameters. These variables and the fundus autofluorescence phenotype were evaluated for prediction of the future square root progression rates using linear mixed-effects models. RESULTS: For the combined model, leave-one-out cross validation on patient level (Scenario 1: previously unknown patient) resulted in a goodness-to-fit (R value) of 0.244 and leave-one-out cross validation on visit level (Scenario 2: previous observation of the patient) in a R value of 0.391. This indicated that shape-descriptive factors could explain 24.4% of the variance in geographic atrophy progression in previously unknown patients and 39.1% in patients with previous observation. CONCLUSION: These findings confirm the relevance of shape-descriptive factors and previous progression as prognostic variables for geographic atrophy progression. However, a substantial part of the remaining variation in geographic atrophy progression seems to depend on other variables, some of which are visible in optical coherence tomography.

[Dry Age-Related Macular Degeneration - Epidemiology and Classification]. / Trockene altersabhängige Makuladegeneration ­ Epidemiologie und Klassifikation.

Age-related macular degeneration (AMD) is clinically divided into early and late stages. The term "dry" AMD is widely used when there are no "exudative" changes in the ocular fundus. There are numerous studies on the epidemiology of AMD. Most studies differentiate between early and late forms of AMD, but without further differentiation of the "dry" late form. In addition, different studies may employ different classifications of AMD, which inevitably leads to deviations in epidemiological data on AMD. New classification systems take into account microstructural changes that can be detected by high resolution in vivo imaging of the retina. A new consensus classification of AMD-associated atrophy will allow future studies to be conducted according to uniform definitions.

QUANTIFICATION OF INTRARETINAL HARD EXUDATES IN EYES WITH DIABETIC RETINOPATHY BY OPTICAL COHERENCE TOMOGRAPHY.

PURPOSE: To evaluate the reproducibility of intraretinal hard exudate (HE) quantification from spectral domain optical coherence tomography (SD-OCT) images of eyes with diabetic retinopathy (DR). METHODS: Cases with diabetic macular edema were enrolled. The area of HE obtained by B-scan segmentation was compared with the area obtained by en face segmentation. RESULTS: The mean ± SD for the HE area was 1.78 ± 1.37 mm with B-scan segmentation and 0.72 ± 0.82 mm with the automated en face analysis tool; the absolute difference was 1.01 ± 0.64 mm. There was excellent correlation in total HE area between the two methods (r = 0.95, P < 0.0001). The HE volume was 0.06 ± 0.07 mm. The correlation between HE volume and en face HE area was high (r = 0.95, P < 0.001). Intergrader reproducibility yielded excellent agreement with an intraclass correlation coefficient value of 0.99 (95% CI 0.994-0.999) for the en face approach and 0.99 (95% CI 0.977-0.997) for manual segmentation. CONCLUSION: Quantification of HE in eyes with diabetic retinopathy can be performed reliably using en face segmentation and, though the en face results are consistently lower, correlates well with HE measurements obtained by exhaustive segmentation of all B-scans in dense volume optical coherence tomography (OCT).

Longitudinal Analysis of Drusen Volume in Intermediate Age-Related Macular Degeneration Using Two Spectral-Domain Optical Coherence Tomography Scan Patterns.

PURPOSE: To evaluate two different spectral-domain optical coherence tomography (SD-OCT) scan patterns in eyes with intermediate age-related macular degeneration (AMD) for the longitudinal assessment of drusen volume. METHODS: The data of 38 eyes of 38 AMD patients (age 69.97 ± 6.08 years) were included. The longitudinal drusen volume over 4 years was analyzed by annual SD-OCT raster scanning (field size 20 × 15°). Two raster scan patterns (A/B) differed in the distance between neighboring B-scans (240 vs. 30 µm) and in the number of averaged frames (4 vs. 15). RESULTS: The mean drusen volume at baseline was 0.213 ± 0.100 mm3 (pattern A) and 0.219 ± 0.103 mm3 (pattern B) (p = 0.937). Linear mixed-effect models showed no significant difference for the change within 4 years for both pattern A (p = 0.8) and pattern B (p = 0.8). CONCLUSIONS: The results indicate that the performance of interpolation algorithms may be sufficient to balance for less dense raster scanning with regard to quantification of longitudinal drusen volume, which can be used as a surrogate marker for AMD progression in future clinical trials.

Angio-OCT de la zona avascular foveal en ojos con oclusión venosa de la retina.

Objetivo: El objetivo del estudio comprendía visualizar y cuantificar las alteraciones patológicas de la zona avascular foveal (ZAF) mediante angio-OCT en ojos con oclusión venosa de la retina (OVR) en comparación con el ojo contralateral sano. Procedimientos: La angio-OCT se llevó a cabo mediante el sistema Avanti® RTVue 100 XR (Optovue Inc., Fremont, Calif., EE. UU.). Los bordes de la capa vascular superficial (CVS) se definieron como 3 µm por debajo de la membrana limitante interna y 15 µm por debajo de la capa plexiforme interna y, para la capa vascular profunda (CVP), como 15 y 70 µm por debajo de la membrana limitante interna y de la capa plexiforme interna, respectivamente. La longitud de la ZAF horizontal, vertical y máxima de la CVS y la CVP en cada ojo se midió de forma manual. Además, se midió el ángulo entre el diámetro máximo de la ZAF y el plano papilomacular. Resultados: La angio-OCT representó los defectos dentro de la vasculatura en el área perifoveal en ojos con oclusión de rama venosa de la retina (ORVR; n = 11) y con oclusión de la vena central de la retina (OVCR; n = 8). Esto resultó en un crecimiento del diámetro máximo de la ZAF en ojos con OVR (n = 19) en comparación con el ojo contralateral (n = 19; 921 ± 213 frente a 724 ± 145 µm; p = 0,008). Además, se observó una correlación significativa entre la mejor agudeza visual corregida (MAVC) y el diámetro máximo de la ZAF en la CVP (ρ de Spearman = -0,423, p < 0,01). Por último, en los ojos con OVR, el ángulo entre el plano papilomacular y el diámetro máximo de la ZAF se dio tan solo en el 21,05% (CVS) y en el 15,79% (CVP) de los casos a 0 ± 15 ó 90 ± 15°, respectivamente. En ojos sanos, estos ángulos (que supuestamente representan una configuración de la ZAF regular) fueron más prevalentes (CVS 68,42 frente a 21,05%, p = 0,003; CVP 73,68 frente a 15,79%, p < 0,001). Conclusiones: La angio-OCT muestra alteraciones morfológicas de la ZAF en ojos con OVCR y ORVR. La correlación del diámetro máximo de la ZAF con la MAVC indica que estas alteraciones resultan funcionalmente relevantes.

Test-Retest Reliability of Scotopic and Mesopic Fundus-Controlled Perimetry Using a Modified MAIA (Macular Integrity Assessment) in Normal Eyes.

PURPOSE: To assess the intrasession test-retest reliability of scotopic cyan and scotopic red fundus-controlled perimetry (FCP) in normal subjects using a modified MAIA "microperimeter" (macular integrity assessment) device. METHODS: Forty-seven normal eyes of 30 subjects (aged 33.8 years) underwent duplicate mesopic (achromatic stimuli, 400-800 nm), scotopic cyan (505 nm), and scotopic red (627 nm) FCP, using a grid of 49 stimuli over 14° of the central retina. Test-retest reliability for pointwise sensitivity (PWS), stability of fixation, reaction time and test duration were analyzed using mixed-effects models. RESULTS: PWS test-retest reliability was good among all 3 types of retinal sensitivity assessments (coefficient of repeatability of 4.75 dB for mesopic, 5.26 dB for scotopic cyan, and 4.06 dB for scotopic red testing). While the mean sensitivity decreased with eccentricity for both mesopic and scotopic red testing, it was highest at 7° eccentricity for the scotopic cyan assessment (p < 0.001). CONCLUSIONS: The modified MAIA device allows for reliable scotopic FCP in normal subjects. Our findings suggest that testing of scotopic cyan sensitivity largely reflects rod function.

Optical coherence tomography angiography of the foveal avascular zone in diabetic retinopathy.

PURPOSE: To analyze foveal avascular zone (FAZ) dimensions and symmetry in patients with diabetic retinopathy (DR) compared to healthy controls using optical coherence tomography angiography (OCT angiography). METHODS: OCT angiography was performed via an Avanti® RTVue 100 XR OCT system (Optovue, Inc., Fremont, CA, USA) in patients with diabetes mellitus (DM) and healthy adults. A frame centered on the fovea was used for FAZ measurements. The borders of the superficial vascular layer were defined as 3 µm below the internal limiting membrane (ILM) and 15 µm below the inner plexiform layer (IPL), and for the deep vascular layer as15 µm and 70 µm below the IPL, respectively. Angles of maximum FAZ diameter were measured in all eyes by two graders. RESULTS: In healthy eyes (N = 25), the FAZ surrounding vascular arcades were intact, showing a vertical or horizontal oval symmetrical formation with a maximum diameter usually on the horizontal or vertical axis. Diabetic eyes (N = 29) presented with disintegrity of the vascular arcades, resulting in an enlarged FAZ. In the superficial layer, the mean horizontal FAZ diameter was significantly larger in the DR group (753 µm ±272 µm) than in the control group (573 µm ±177 µm, p = 0.029). The difference was even more pronounced in the deep layer, with a mean value of 659 µm ±194 µm in the control group and 1009 µm ±342 µm in the DR group (p = 0.001). Furthermore, in the superficial layer, the angle of the maximum FAZ diameter was 0° (±15°) or 90° (±15°) in 72.0 % of healthy eyes. In eyes with DR, the angle was 0° (±15°) or 90° (±15°) in only 6.9 % of cases, due to the irregular configuration of the FAZ. CONCLUSIONS: OCT angiography is capable of imaging retinal vasculature without dye injection. Our data suggest that it can detect disintegrity of the vascular arcades surrounding the FAZ, thus differentiating DM from healthy eyes. Vascular abnormalities were more pronounced in the deep vascular layer.

Optical Coherence Tomography Angiography of the Foveal Avascular Zone in Retinal Vein Occlusion.

PURPOSE: The aim of the study was to visualize and to quantify pathological foveal avascular zone (FAZ) alterations through optical coherence tomography angiography (OCT-A) in eyes with retinal vein occlusion (RVO) in comparison to the unaffected fellow eyes. PROCEDURES: OCT-A was conducted with the Avanti® RTVue 100 XR system (Optovue Inc., Fremont, Calif., USA). The borders of the superficial vascular layer (SVL) were defined as 3 µm below the internal limiting membrane and 15 µm below the inner plexiform layer, and for the deep vascular layer (DVL) as 15 and 70 µm below the inner plexiform layer, respectively. The length of the horizontal, vertical and maximum FAZ was manually measured for the SVL and DVL in each eye. Additionally, the angle between the maximum FAZ diameter and the papillomacular plane was measured. RESULTS: OCT-A depicted defects within the perifoveal vasculature in eyes with branch retinal vein occlusion (BRVO; n = 11) and central retinal vein occlusion (CRVO; n = 8). These resulted in an enlargement of the maximum FAZ diameter in eyes with RVO (n = 19) in comparison to the healthy fellow eyes (n = 19; 921 ± 213 vs. 724 ± 145 µm; p = 0.008). Furthermore, a significant correlation was found between best-corrected visual acuity (BCVA) and the maximum FAZ diameter in the DVL (Spearman's x03C1; = -0.423, p < 0.01). Lastly, in the eyes with RVO, the angle between the papillomacular plane and the maximum FAZ diameter was only in 21.05% (SVL) and 15.79% (DVL) of the cases at 0 ± 15 or 90 ± 15°, respectively. In healthy eyes, these angles (which putatively represent a regular FAZ configuration) were more prevalent (SVL 68.42 vs. 21.05%, p = 0.003; DVL 73.68 vs. 15.79%, p < 0.001). CONCLUSION: OCT-A shows morphological alterations of the FAZ in eyes with CRVO and BRVO. The correlation of the maximum FAZ diameter with BCVA suggests that these alterations are functionally relevant.

An extended helical conformation in domain 3a of Munc18-1 provides a template for SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex assembly.

Munc18-1, a SEC1/Munc18 protein and key regulatory protein in synaptic transmission, can either promote or inhibit SNARE complex assembly. Although the binary inhibitory interaction between Munc18-1 and closed syntaxin 1 is well described, the mechanism of how Munc18-1 stimulates membrane fusion remains elusive. Using a reconstituted assay that resolves vesicle docking, priming, clamping, and fusion during synaptic exocytosis, we show that helix 12 in domain 3a of Munc18-1 stimulates SNAREpin assembly and membrane fusion. A single point mutation (L348R) within helix 12 selectively abolishes VAMP2 binding and the stimulatory function of Munc18-1 in membrane fusion. In contrast, targeting a natural switch site (P335A) at the start of helix 12, which can result in an extended α-helical conformation, further accelerates lipid-mixing. Together with structural modeling, the data suggest that helix 12 provides a folding template for VAMP2, accelerating SNAREpin assembly and membrane fusion. Analogous SEC1/Munc18-SNARE interactions at other transport steps may provide a general mechanism to drive lipid bilayer merger. At the neuronal synapse, Munc18-1 may convert docked synaptic vesicles into a readily releasable pool.