Faculty Bibliography

PURPOSE/OBJECTIVE:To analyze the spectrum of ischemia associated with paracentral acute middle maculopathy (PAMM) in eyes with acute retinal vascular occlusion and to describe an ischemic cascade. DESIGN/METHODS:A retrospective observational case series. METHODS:Patients presenting with PAMM secondary to acute retinal vascular occlusion were identified. Analysis of multimodal imaging was performed at baseline and at follow up visits to elucidate the patterns and progression of ischemia within the retinal layers. RESULTS:Multimodal retinal imaging from 16 eyes of 16 patients with acute retinal vascular occlusion associated with PAMM was studied. Analysis of en face OCT segmentation of the inner nuclear layer (INL) identified distinct patterns of PAMM correlating with the severity of ischemia and not the type of occlusion. A perivenular fern-like PAMM pattern was associated with better visual outcomes (average final visual acuity was 20/25). This pattern was noted to sequentially progress in 2 cases to a diffuse globular PAMM pattern in the INL, or to a pattern of ischemia involving both the middle and inner retinal layers with commensurate vision loss. Globular patterns of PAMM or ischemia involving both the middle and inner retina correlated with poorer visual outcomes (average final visual acuity was counting fingers at 5.5 ft). These various patterns of ischemia developed in eyes with retinal vascular occlusions in which blood flow through the retinal capillary plexuses was present but was significantly reduced and delayed. CONCLUSIONS:This study describes OCT findings suggestive of an ischemic cascade in eyes with retinal vascular occlusion. The middle retina at the level of the deep capillary plexus, especially at the venular pole, may be more vulnerable to ischemic injury.

The recent introduction of optical coherence tomography angiography (OCTA) has remarkably expanded our knowledge of the choroid through in vivo investigation of the anatomical and pathological features of this important vascular layer. New insights elucidating the morphological features of the choroid, in both physiological and pathological conditions, indicate that this vascular structure plays a crucial role in many chorioretinal disorders. In this article, a review of the salient histological and anatomical features of the choroid, essential for the proper interpretation of in vivo imaging, is followed by a discussion of the fundamental principles of OCTA and the application of this advanced imaging modality to study and understand the choroid. The current limitations of OCTA and potential advancements that may improve the widespread adoption of this tool are also discussed. A detailed review of the OCTA features of the choroid in the healthy eye is followed by relevant findings in major chorioretinal diseases, including age-related macular degeneration, central serous chorioretinopathy, uveitis, and inherited retinal disorders.

Purpose/UNASSIGNED:To determine if inner retinal layer reflectivity in eyes with acute central retinal vein occlusion (CRVO) correlates with visual acuity at 12 months. Methods/UNASSIGNED:Macular optical coherence tomography (OCT) scans were obtained from 22 eyes of 22 patients with acute CRVO. Optical intensity ratios (OIRs), defined as the mean OCT reflectivity of the inner retinal layers normalized to the mean reflectivity of the RPE, were measured from the presenting and 1-month OCT image by both manual measurements of grayscale B-scans and custom algorithmic measurement of raw OCT volume data. OIRs were assessed for association with final visual outcome. Cohort subgroup division for analysis was determined statistically. Results/UNASSIGNED:Eyes with poorer final visual acuity (≥20/70) at 1 year were more likely to have a higher ganglion cell layer OIR than eyes with better final visual acuity (<20/70) at 1 month (manually: 0.591 to 0.735, P = 0.006, algorithmically: 0.663 to 0.799, P = 0.014). At 1 month, eyes with a poorer final visual acuity demonstrated a higher variance of OIR measurements (algorithmically: 0.087 vs. 0.160, P = 0.002) per scan than eyes with better final visual acuity. Conclusions/UNASSIGNED:In acute CRVO, ganglion cell layer changes at 1 month, including increased reflectivity and increased heterogeneity of reflectivity signal as expressed as OIR and OIR variance, were associated with a poorer visual prognosis at 1 year. Technique calibration with larger sample sizes and automated integration into OCT platforms will be necessary to determine if OIR can be a clinically useful prognostic tool.

Nonneovascular (dry) AMD is a retinal disease with potential for significant central visual impairment. The hallmarks of this disease are macular drusen, RPE alterations, and geographic atrophy (GA). Classification schemes for nonneovascular AMD have evolved over the years as major advances in retinal imaging have enabled a greater understanding of disease pathophysiology. The original classifications of nonneovascular AMD were based on color fundus photography (CFP), while more modern schemes rely on a multimodal imaging approach. Effective diagnosis and management of nonneovascular AMD requires a thorough understanding of its multimodal imaging features as detailed in this review. Future imaging modalities and imaging biomarkers that may aid in diagnosis and management are also discussed.

PURPOSE/OBJECTIVE:In an eye with macular atrophy due to age-related macular degeneration (AMD; complete retinal pigment epithelium (RPE) and outer retinal atrophy (cRORA)), we correlated in vivo imaging to histology to characterize the atrophy border and evaluate the utility of optical coherence tomography (OCT) metrics suggested by previous histology. DESIGN/METHODS:Case study with clinicopathologic correlation. METHOD/METHODS:In vivo eye-tracked cross-sectional OCT scans at 13 and 8 months before death were compared to post-mortem histopathology. On OCT, the atrophy border was identified as either the descent of the external limiting membrane (ELM) towards Bruch's membrane (BrM) (representing gliosis), or the presence of choroidal hypertransmission (representing lack of shadowing by RPE). Thicknesses of RPE, basal laminar deposit (BLamD), and BrM was measured at 500 and 100 μm on the non-atrophic and atrophic sides of these borders, on in vivo eye-tracked OCT and histology matched to the same location. RESULTS:In all OCT scans, the ELM descent was visible. The RPE-BLamD band significantly thickened towards it (p<0.005), over time (p=0.015 and 0.043, at 500 and 100 μm, respectively). On OCT, the ELM descent delineated a smaller atrophic area than did hypertransmission. RPE-BLamD thicknesses manually measured on OCT overestimated histological thicknesses. BrM visibility varied with RPE status. CONCLUSION/CONCLUSIONS:Visible on OCT, the ELM descent is a histopathologic atrophy border supporting new terminology of cRORA, whereas hypertransmission reveals RPE degeneration. RPE-BLamD thickening across the macula, towards the atrophy and over time is confirmed. The presence of gliosis and thick RPE-BLamD suggests that macular atrophy is a late stage in disease progression, encouraging anatomical endpoints at earlier AMD stages, rather than atrophy enlargement.

PURPOSE:To evaluate the size and location of macular atrophy in eyes with Type-1 neovascularization (NV) and age-related macular degeneration receiving chronic intravitreal anti-vascular endothelial growth factor therapy. METHODS:A retrospective review of a case series of 27 eyes with Type-1 NV and retinal pigment epithelial detachment (PED) having a minimum of 12 months follow-up was performed. Demographic information and visual acuity at baseline and the final follow-up were collected. Spectral-domain optical coherence tomography (OCT) and near-infrared reflectance were analyzed at 6-month intervals to detect and measure macular atrophy. Location and area (in square millimeter) of macular atrophy were measured using Heidelberg software tools. Also, OCT angiography was used to colocalize the area of Type-1 NV flow versus the location of atrophy. RESULTS:Twenty-seven eyes of 27 patients were included in this analysis. The median visual acuity was 20/50, mean age was 82.7 years, and mean number of injections was 29.5. A larger percentage of eyes (59.3%) developed atrophy predominantly eccentric to the PED versus predominantly overlying the PED (11.1%) when measured with spectral-domain OCT and near-infrared imaging. At the final follow-up, there was a larger area of atrophy surrounding the fibrovascular PED (mean, 3.326 mm) than overlying it (mean, 0.542 mm), and this was statistically significant (P = 0.0118). En-face OCT images were overlaid with OCT angiography in 11 eyes, and a predominantly eccentric pattern of atrophy was identified in 9 of 11 eyes. Using this method, the mean area of atrophy predominantly overlying the Type-1 NV was 1.652 mm (range of 0-10.464 mm), whereas the area of atrophy predominantly eccentric to the neovascular complex was 4.345 mm (range of 0.705-13.758 mm), and this was statistically significant (P = 0.0465). The average rate of atrophy progression was 1.04 mm/year (SD 0.938). CONCLUSION:With long-term anti-vascular endothelial growth factor therapy for eyes with Type-1 NV secondary to age-related macular degeneration, macular atrophy tends to develop predominantly eccentric to the PED and the neovascular flow imaged on OCT angiography. With chronic vascular endothelial growth factor suppression, Type-1 NV may evolve into a multilayered PED that may confer a protective effect to the overlying retinal pigment epithelium and outer retina.

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PURPOSE/OBJECTIVE:To study choriocapillaris (CC) flow in eyes with Type 3 neovascularization (NV) and age-related macular degeneration, using optical coherence tomography angiography analysis. METHODS:In this multicenter, retrospective, observational study, we collected data from 21 patients with unilateral Type 3 NV and age-related macular degeneration, based on clinical examination, structural optical coherence tomography, and fluorescein angiography when available. An additional group of 20 nonneovascular age-related macular degeneration eyes with unilateral Type 1 or Type 2 NV due to age-related macular degeneration was included for comparison. En face optical coherence tomography angiography imaging (3 × 3 mm scans) with quantitative microvascular analysis of the CC was performed. Main outcome measures were: 1) the percent nonperfused choriocapillaris area; and 2) the average CC signal void size. RESULTS:We included 21 patients with unilateral Type 3 NV (15 female, 71.5%) and 20 patients with unilateral Type 1 or 2 NV (9 female, 45.0% P = 0.118). Mean ± SD age was 82.1 ± 7.4 years in the unilateral Type 3 patients and 78.3 ± 8.1 in unilateral Type 1/2 NV subjects (P = 0.392). The percent nonperfused choriocapillaris area was 56.3 ± 8.1% in eyes with Type 3 NV and 51.9 ± 4.3% in the fellow eyes (P = 0.016). The average signal void size was also increased in those eyes with Type 3 NV (939.9 ± 680.9 μm), compared with the fellow eyes (616.3 ± 304.2 μm, P = 0.039). The number of signal voids was reduced in the Type 3 NV eyes (604.5 ± 282.9 vs. 747.3 ± 195.8, P = 0.046). The subfoveal choroidal thickness was 135.9 ± 54.2 μm in eyes with Type 3 NV and 167.2 ± 65.4 μm in the fellow eyes (P = 0.003). In addition, the fellow eyes of patients with unilateral Type 3 NV displayed more significant CC flow abnormalities versus the fellow eyes with unilateral Type 1/2 NV (percent nonperfused choriocapillaris area = 51.9 ± 4.3% vs. 46.0 ± 2.1%, respectively, P < 0.0001; and average signal void size 616.3 ± 304.2 μm versus 351.4 ± 65.5 μm, respectively, P < 0.0001; and number of signal voids 747.3 ± 195.8 vs. 998.5 ± 147.3, respectively, P < 0.0001). CONCLUSION/CONCLUSIONS:Eyes with unilateral Type 3 NV illustrated increased CC nonperfusion versus fellow nonneovascular eyes. These results suggest that choroidal ischemia may play an important role in the development of Type 3 NV.

Conventionally rendered optical coherence tomography (OCT) images of the posterior segment contain shadows which influence the visualization of deep structures such as the choroid. The purpose of this study was to determine whether OCT shadow compensation (SC) alters the appearance of the choroid and the apparent choroidal vascularity index (CVI), an OCT-derived estimated ratio of luminal to total choroidal volume. All scans were shadow compensated using a previously published algorithm, binarized using a novel validated algorithm and extracted binarized choroid to estimate CVI. On 27 raw swept-source OCT volume-scans of healthy subjects, the effect of SC on CVI was established both qualitatively and quantitatively. In shadow compensated scans, the choroid was visualized with greater brightness than the neurosensory retina and the masking of deep tissues by retinal blood vessels was greatly reduced. Among study subjects, significant mean difference in CVI of -0.13 was observed between raw and shadow compensated scans. Conventionally acquired OCT underestimates both choroidal reflectivity and calculated CVI. Quantitative analysis based on subjective grading demonstrated that SC increased the contrast between stromal and luminal regions and are in agreement with true tissue regions. This study is warranted to determine the effects of SC on CVI in diseased eyes.

PURPOSE/OBJECTIVE:To systematically characterize histologic features of multiple chorioretinal layers in eyes with geographic atrophy, or complete retinal pigment epithelium (RPE) and outer retinal atrophy, secondary to age-related macular degeneration, including Henle fiber layer and outer nuclear layer; and to compare these changes to those in the underlying RPE-Bruch membrane-choriocapillaris complex and associated extracellular deposits. METHODS:Geographic atrophy was delimited by the external limiting membrane (ELM) descent towards Bruch membrane. In 13 eyes, histologic phenotypes and/or thicknesses of Henle fiber layer, outer nuclear layer, underlying supporting tissues, and extracellular deposits at four defined locations on the non-atrophic and atrophic sides of the ELM descent were assessed and compared across other tissue layers, with generalized estimating equations and logit models. RESULTS:On the non-atrophic side of the ELM descent, distinct Henle fiber layer and outer nuclear layer became dyslaminated, cone photoreceptor inner segment myoids shortened, photoreceptor nuclei and mitochondria translocated inward, and RPE was dysmorphic. On the atrophic side of the ELM descent, all measures of photoreceptor health declined to zero. Henle fiber layer/outer nuclear layer thickness halved, and only Müller cells remained, in the absence of photoreceptors. Sub-RPE deposits remained, Bruch membrane thinned, and choriocapillaris density decreased. CONCLUSION/CONCLUSIONS:The ELM descent sharply delimits an area of marked gliosis and near-total photoreceptor depletion clinically defined as Geographic atrophy (or outer retinal atrophy), indicating severe and potentially irreversible tissue damage. Degeneration of supporting tissues across this boundary is gradual, consistent with steady age-related change and suggesting that RPE and Müller cells subsequently respond to a threshold of stress. Novel clinical trial endpoints should be sought at age-related macular degeneration stages before intense gliosis and thick deposits impede therapeutic intervention.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.