Geographic atrophy: a histopathological assessment

Microperimetry Characteristics of Regions With a Truly Nonresponding Location: Implications for Atrophic Age-Related Macular Degeneration

Purpose

To understand the microperimetry response characteristics of regions with a truly nonresponding location, which will be useful when considering criteria for end-stage atrophic age-related macular degeneration (AMD).

Methods

A simulation model was developed using data from 128 participants with bilateral large drusen at baseline seen over 36 months at 6-month intervals. One hundred thousand pairs of real-world microperimetry testing results were simulated separately with and without one truly nonresponding location, where the sensitivity of one randomly selected location for the former group was derived from the distribution of responses from a truly nonresponding location at the optic nerve head from 60 healthy participants.

Results

Only 60% of the simulated test pairs with a truly nonresponding location had ≥1 location that was <0 decibel (dB) on both tests. In contrast, 91% of the simulated test pairs had ≥1 location that was ≤10 dB on both tests, and 87% had ≥1 location that was ≤10 dB on both tests and <0 dB for one of the tests. Of the simulated test pairs without a truly nonresponding location, there were 0.04%, 1.4%, and 0.4% that met these three above criteria, respectively.

Conclusions

Regions with a truly nonresponding test location do not almost always show a repeatable absolute scotoma (<0 dB), but instead, much more often a deep visual sensitivity defect (≤10 dB), with or without having an absolute scotoma on one of the tests. These findings are crucial if functional criteria are to be considered as part of a definition of end-stage atrophic AMD.

DIRECTIONAL OPTICAL COHERENCE TOMOGRAPHY IMAGING OF MACULAR PATHOLOGY

PURPOSE

To survey the impact of directional reflectivity on structures within optical coherence tomography images in retinal pathology.

METHODS

Sets of commercial optical coherence tomography images taken from multiple pupil positions were analyzed. These directional optical coherence tomography sets revealed directionally reflective structures within the retina. After ensuring sufficient image quality, resulting hybrid and composite images were characterized by assessing the Henle fiber layer, outer nuclear layer, ellipsoid zone, and interdigitation zone. Additionally, hybrid images were reviewed for novel directionally reflective pathological features.

RESULTS

Cross-sectional directional optical coherence tomography image sets were obtained in 75 eyes of 58 patients having a broad range of retinal pathologies. All cases showed improved visualization of the outer nuclear layer/Henle fiber layer interface, and outer nuclear layer thinning was, therefore, more apparent in several cases. The ellipsoid zone and interdigitation zone also demonstrated attenuation where a geometric impact of underlying pathology affected their orientation. Misdirected photoreceptors were also noted as a consistent direction-dependent change in ellipsoid zone reflectivity between regions of normal and absent ellipsoid zone.

CONCLUSION

Directional optical coherence tomography enhances the understanding of retinal anatomy and pathology. This optical contrast yields more accurate identification of retinal structures and possible imaging biomarkers for photoreceptor-related pathology.

Long-term Follow-up of a Phase 1/2a Clinical Trial of a Stem Cell-Derived Bioengineered Retinal Pigment Epithelium Implant for Geographic Atrophy

PURPOSE

To report long-term results from a phase 1/2a clinical trial assessment of a scaffold-based human embryonic stem cell-derived retinal pigmented epithelium (RPE) implant in patients with advanced geographic atrophy (GA).

DESIGN

A single-arm, open-label phase 1/2a clinical trial approved by the United States Food and Drug Administration.

PARTICIPANTS

Patients were 69-85 years of age at the time of enrollment and were legally blind in the treated eye (best-corrected visual acuity [BCVA], ≤ 20/200) as a result of GA involving the fovea.

METHODS

The clinical trial enrolled 16 patients, 15 of whom underwent implantation successfully. The implant was administered to the worse-seeing eye with the use of a custom subretinal insertion device. The companion nonimplanted eye served as the control. The primary endpoint was at 1 year; thereafter, patients were followed up at least yearly.

MAIN OUTCOME MEASURES

Safety was the primary endpoint of the study. The occurrence and frequency of adverse events (AEs) were determined by scheduled eye examinations, including measurement of BCVA and intraocular pressure and multimodal imaging. Serum antibody titers were collected to monitor systemic humoral immune responses to the implanted cells.

RESULTS

At a median follow-up of 3 years, fundus photography revealed no migration of the implant. No unanticipated, severe, implant-related AEs occurred, and the most common anticipated severe AE (severe retinal hemorrhage) was eliminated in the second cohort (9 patients) through improved intraoperative hemostasis. Nonsevere, transient retinal hemorrhages were noted either during or after surgery in all patients as anticipated for a subretinal surgical procedure. Throughout the median 3-year follow-up, results show that implanted eyes were more likely to improve by > 5 letters of BCVA and were less likely to worsen by > 5 letters compared with nonimplanted eyes.

CONCLUSIONS

This report details the long-term follow-up of patients with GA to receive a scaffold-based stem cell-derived bioengineered RPE implant. Results show that the implant, at a median 3-year follow-up, is safe and well tolerated in patients with advanced dry age-related macular degeneration. The safety profile, along with the early indication of efficacy, warrants further clinical evaluation of this novel approach for the treatment of GA.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Pegcetacoplan Treatment and Consensus Features of Geographic Atrophy Over 24 Months

Importance

Despite widespread availability and consensus on its advantages for detailed imaging of geographic atrophy (GA), spectral-domain optical coherence tomography (SD-OCT) might benefit from automated quantitative OCT analyses in GA diagnosis, monitoring, and reporting of its landmark clinical trials.

Objective

To analyze the association between pegcetacoplan and consensus GA SD-OCT end points.

Design, Setting, and Participants

This was a post hoc analysis of 11 614 SD-OCT volumes from 936 of the 1258 participants in 2 parallel phase 3 studies, the Study to Compare the Efficacy and Safety of Intravitreal APL-2 Therapy With Sham Injections in Patients With Geographic Atrophy (GA) Secondary to Age-Related Macular Degeneration (OAKS) and Study to Compare the Efficacy and Safety of Intravitreal APL-2 Therapy With Sham Injections in Patients With Geographic Atrophy (GA) Secondary to Age-Related Macular Degeneration (DERBY). OAKS and DERBY were 24-month, multicenter, randomized, double-masked, sham-controlled studies conducted from August 2018 to July 2020 among adults with GA with total area 2.5 to 17.5 mm2 on fundus autofluorescence imaging (if multifocal, at least 1 lesion ≥1.25 mm2). This analysis was conducted from September to December 2023.

Interventions

Study participants received pegcetacoplan, 15 mg per 0.1-mL intravitreal injection, monthly or every other month, or sham injection monthly or every other month.

Main Outcomes and Measures

The primary end point was the least squares mean change from baseline in area of retinal pigment epithelium and outer retinal atrophy in each of the 3 treatment arms (pegcetacoplan monthly, pegcetacoplan every other month, and pooled sham [sham monthly and sham every other month]) at 24 months. Feature-specific area analysis was conducted by Early Treatment Diabetic Retinopathy Study (ETDRS) regions of interest (ie, foveal, parafoveal, and perifoveal).

Results

Among 936 participants, the mean (SD) age was 78.5 (7.22) years, and 570 participants (60.9%) were female. Pegcetacoplan, but not sham treatment, was associated with reduced growth rates of SD-OCT biomarkers for GA for up to 24 months. Reductions vs sham in least squares mean (SE) change from baseline of retinal pigment epithelium and outer retinal atrophy area were detectable at every time point from 3 through 24 months (least squares mean difference vs pooled sham at month 24, pegcetacoplan monthly: -0.86 mm2; 95% CI, -1.15 to -0.57; P < .001; pegcetacoplan every other month: -0.69 mm2; 95% CI, -0.98 to -0.39; P < .001). This association was more pronounced with more frequent dosing (pegcetacoplan monthly vs pegcetacoplan every other month at month 24: -0.17 mm2; 95% CI, -0.43 to 0.08; P = .17). Stronger associations were observed in the parafoveal and perifoveal regions for both pegcetacoplan monthly and pegcetacoplan every other month.

Conclusions and Relevance

These findings offer additional insight into the potential effects of pegcetacoplan on the development of GA, including potential effects on the retinal pigment epithelium and photoreceptors.

Trial Registration

ClinicalTrials.gov Identifiers: NCT03525600 and NCT03525613.

Imaging geographic atrophy: integrating structure and function to better understand the effects of new treatments

Geographic atrophy (GA) is an advanced and irreversible form of age-related macular degeneration (AMD). Chronic low grade inflammation is thought to act as an initiator of this degenerative process, resulting in loss of photoreceptors (PRs), retinal pigment epithelium (RPE) and the underlying choriocapillaris. This review examined the challenges of clinical trials to date which have sought to treat GA, with particular reference to the successful outcome of C3 complement inhibition. Currently, optical coherence tomography (OCT) seems to be the most suitable method to detect GA and monitor the effect of treatment. In addition, the merits of using novel anatomical endpoints in detecting GA expansion are discussed. Although best-corrected visual acuity is commonly used to monitor disease in GA, other tests to determine visual function are explored. Although not widely available, microperimetry enables quantification of retinal sensitivity (RS) and macular fixation behaviour related to fundus characteristics. There is a spatial correlation between OCT/fundus autofluorescence evaluation of PR damage outside the area of RPE loss and RS on microperimetry, showing important associations with visual function. Standardisation of testing by microperimetry is necessary to enable this modality to detect AMD progression. Artificial intelligence (AI) analysis has shown PR layers integrity precedes and exceeds GA loss. Loss of the ellipsoid zone has been recognised as a primary outcome parameter in therapeutic trials for GA. The integrity of the PR layers imaged by OCT at baseline has been shown to be an important prognostic indicator. AI has the potential to be invaluable in personalising care and justifying treatment intervention.

Retinal neurodegeneration in age-related macular degeneration

Age-related macular degeneration (AMD) is a complex and multifactorial disease characterized by the damage of the unit comprised of the photoreceptors, retinal pigment epithelium (RPE), Bruch's membrane, and choriocapillaris. Although the outer retina appears to be mainly affected in this disorder, several evidences exhibit that also the inner retina may be impaired. In this review we will provide a description of the prominent histologic and imaging findings suggesting an inner retinal loss in these eyes. In details, structural optical coherence tomography (OCT) technology proved either the inner and outer retina is impacted by AMD and that these two impairments are associated. Therefore, the purpose of this review is to provide a description of the role of neurodegeneration in AMD in order to better understand the relationship between neuronal loss and the outer retinal damage in this disease.

Deep-learning automated quantification of longitudinal OCT scans demonstrates reduced RPE loss rate, preservation of intact macular area and predictive value of isolated photoreceptor degeneration in geographic atrophy patients receiving C3 inhibition treatment

OBJECTIVE

To evaluate the role of automated optical coherence tomography (OCT) segmentation, using a validated deep-learning model, for assessing the effect of C3 inhibition on the area of geographic atrophy (GA); the constituent features of GA on OCT (photoreceptor degeneration (PRD), retinal pigment epithelium (RPE) loss and hypertransmission); and the area of unaffected healthy macula.To identify OCT predictive biomarkers for GA growth.

METHODS

Post hoc analysis of the FILLY trial using a deep-learning model for spectral domain OCT (SD-OCT) autosegmentation. 246 patients were randomised 1:1:1 into pegcetacoplan monthly (PM), pegcetacoplan every other month (PEOM) and sham treatment (pooled) for 12 months of treatment and 6 months of therapy-free monitoring. Only participants with Heidelberg SD-OCT were included (n=197, single eye per participant).The primary efficacy endpoint was the square root transformed change in area of GA as complete RPE and outer retinal atrophy (cRORA) in each treatment arm at 12 months, with secondary endpoints including RPE loss, hypertransmission, PRD and intact macular area.

RESULTS

Eyes treated PM showed significantly slower mean change of cRORA progression at 12 and 18 months (0.151 and 0.277 mm, p=0.0039; 0.251 and 0.396 mm, p=0.039, respectively) and RPE loss (0.147 and 0.287 mm, p=0.0008; 0.242 and 0.410 mm, p=0.00809). PEOM showed significantly slower mean change of RPE loss compared with sham at 12 months (p=0.0313). Intact macular areas were preserved in PM compared with sham at 12 and 18 months (p=0.0095 and p=0.044). PRD in isolation and intact macula areas was predictive of reduced cRORA growth at 12 months (coefficient 0.0195, p=0.01 and 0.00752, p=0.02, respectively) CONCLUSION: The OCT evidence suggests that pegcetacoplan slows progression of cRORA overall and RPE loss specifically while protecting the remaining photoreceptors and slowing the progression of healthy retina to iRORA.

Functional Evaluation of Retinal Pigment Epithelium and Outer Retinal Atrophy by High-Density Targeted Microperimetry Testing

Purpose

Complete retinal pigment epithelium (RPE) and outer retinal atrophy (cRORA) on OCT imaging has recently been proposed to describe end-stage atrophy in age-related macular degeneration (AMD) by international consensus and expected to be associated with a dense scotoma, but such functional evidence is lacking. This study sought to examine the visual sensitivity defects associated with cRORA and to determine OCT features associated with deep defects.

Design

Observational study.

Participants

Sixty eyes from 53 participants, including 342 microperimetry tests over 171 study visits.

Methods

Participants underwent targeted high-density threshold-based microperimetry testing of atrophic lesions (with at least incomplete RPE and outer retinal atrophy [iRORA]) with a 3.5° diameter grid. The maximum extent of signs of atrophy for all lesions was graded on OCT imaging.

Main Outcome Measures

Number of deep visual sensitivity defects (threshold ≤ 10 decibels [dB]).

Results

Presence of choroidal signal hypertransmission ≥ 500 μm, complete RPE loss ≥250 μm, and inner nuclear layer and outer plexiform layer subsidence, and hyporeflective wedge-shaped band (defined as nascent geographic atrophy [nGA]) ≥ 500 μm (P ≤ 0.020), but not RPE attenuation or disruption (P ≥ 0.192), were all independently associated with a significant increase in the number of deep visual sensitivity defects ≤ 10 dB. Only cRORA lesions with hypertransmission ≥ 500 μm or complete RPE loss ≥ 250 μm, or with both of these features (P < 0.001), but not lesions with only hypertransmission 250-499 μm (P = 0.303), had significantly more deep visual sensitivity defects ≤ 10 dB compared with iRORA lesions. Lesions with nGA ≥ 500 μm, irrespective of the presence of hypertransmission ≥ 500 μm and/or complete RPE loss ≥ 250 μm, also showed a higher number of deep visual sensitivity defects ≤ 10 dB compared with lesions without nGA ≥ 500 μm (P ≤ 0.011).

Conclusions

Not all cRORA lesions show a difference in the number of deep visual sensitivity defects compared with iRORA. Instead, hypertransmission ≥ 500 μm, complete RPE loss ≥ 250 μm, and nGA ≥ 500 μm are all OCT features independently associated with deep visual sensitivity detects that could help inform the definition of end-stage atrophy on OCT imaging.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Histologic and Immunohistochemical Characterization of GA-Like Pathology in the Rat Subretinal Sodium Iodate Model

Purpose

Geographic atrophy (GA) is an advanced form of dry age-related macular degeneration with multifactorial etiology and no well-established treatment. A model recapitulating the hallmarks would serve as a key to understanding the underlying pathologic mechanisms better. In this report, we further characterized our previously reported subretinal sodium iodate model of GA.

Methods

Retinal degeneration was induced in rats (6-8 weeks old) by subretinal injections of NaIO3 as described previously. Animals were sacrificed at 3, 8 and 12 weeks after injection and eyes were fixed or cryopreserved. Some choroids were processed as flatmounts while other eyes were cryopreserved, sectioned, and immunolabeled with a panel of antibodies. Finally, some eyes were prepared for transmission electron microscopic (TEM) analysis.

Results

NaIO3 subretinal injection resulted in a well-defined focal area of retinal pigment epithelium (RPE) degeneration surrounded by viable RPE. These atrophic lesions expanded over time. RPE morphologic changes at the border consisted of hypertrophy, multilayering, and the possible development of a migrating phenotype. Immunostaining of retinal sections demonstrated external limiting membrane descent, outer retinal tubulation (ORT), and extension of Müller cells toward RPE forming a glial membrane in the subretinal space of the atrophic area. TEM findings demonstrated RPE autophagy, cellular constituents of ORT, glial membranes, basal laminar deposits, and defects in Bruch's membrane.

Conclusions

In this study, we showed pathologic features of a rodent model resembling human GA in a temporal order through histology, immunofluorescence, and TEM analysis and gained insights into the cellular and subcellular levels of the GA-like phenotypes.

Translational Relevance

Despite its acute nature, the expansion of atrophy and the GA-like border in this rat model makes it ideal for studying disease progression and provides a treatment window to test potential therapeutics for GA.

Visual Sensitivity Loss in Geographic Atrophy: Structure-Function Evaluation Using Defect-Mapping Microperimetry

Purpose

To examine the structure-function relationship in eyes with geographic atrophy (GA) using defect-mapping microperimetry, a testing strategy optimized to quantify the spatial extent of deep visual sensitivity losses.

Methods

Fifty participants with GA underwent defect-mapping microperimetry testing of the central 8°-radius region (208 locations tested once with a 10-decibel stimuli) and fundus autofluorescence imaging in one eye. The GA extent in the corresponding central 8°-radius was derived by manual annotations and image co-registration to examine the global structure-function relationship. The distance of each test location from the GA margin was also derived, and regions defined, to examine the local structure-function relationship.

Results

GA extent in the central 8° explained a substantial proportion of variance in the percentage of locations missed (nonresponse) on microperimetry at the global level (R2 = 0.90). At a local level, the probability of missing stimuli at the outer junctional zone (0-500 µm outside the GA margin) and GA margin (probability = 7% and 34%, respectively) was higher than at the outer nonlesional zone (>500 µm outside the GA margin; probability = 2%; P < 0.001 for both). The probability of missing stimuli at the inner junctional zone (0-250 µm inside the GA margin) was also lower than at the inner lesional zone (>250 µm inside the GA margin; probability = 64% and 88%; P < 0.001).

Conclusions

This study confirms the expected functional relevance of the region with GA on fundus autofluorescence imaging and underscores the potential effectiveness of defect-mapping microperimetry testing for capturing visual function changes when evaluating new GA treatments.

Assessment of Choriocapillaris Flow Prior to Nascent Geographic Atrophy Development Using Optical Coherence Tomography Angiography

Purpose

To assess the relationship between choriocapillaris (CC) loss and the development of nascent geographic atrophy (nGA) using optical coherence tomography angiography (OCTA) imaging.

Methods

In total, 105 from 62 participants with bilateral large drusen, without late age-related macular degeneration (AMD) or nGA at baseline, were included in this prospective, longitudinal, observational study. Participants underwent swept-source OCTA imaging at 6-month intervals. CC flow deficit percentage (FD%) and drusen volume measurements were determined for the visit prior to nGA development or the second-to-last visit if nGA did not develop. Global and local analyses, the latter based on analyses within superpixels (120 × 120-µm regions), were performed to examine the association between CC FD% and future nGA development.

Results

A total of 15 (14%) eyes from 12 (19%) participants developed nGA. There was no significant difference in global CC FD% at the visit prior to nGA development between eyes that developed nGA and those that did not (P = 0.399). In contrast, CC FD% was significantly higher in superpixels that subsequently developed nGA compared to those that did not (P < 0.001), and a model utilizing CC FD% was significantly better at predicting foci of future nGA development at the superpixel level than a model using drusen volume alone (P ≤ 0.040).

Conclusions

This study showed that significant impairments in CC blood flow could be detected locally prior to the development of nGA. These findings add to our understanding of the pathophysiologic changes that occur with atrophy development in AMD.

Decreased Central Macular Choriocapillaris Perfusion Correlates With Increased Low Luminance Visual Acuity Deficits

PURPOSE

Correlations between low luminance visual acuity deficits (LLVADs) and central choriocapillaris perfusion deficits were investigated to help explain how increases in LLVAD scores at baseline predict annual growth rates of geographic atrophy (GA).

DESIGN

Prospective cross-sectional study.

METHODS

Photopic luminance best-corrected visual acuity (PL-BCVA) and low luminance BCVA (LL-BCVA) were measured using the Early Treatment Diabetic Retinopathy Study chart. LL-BCVA was measured using a 2.0-log unit neutral density filter. LLVADs were calculated as the difference between PL-BCVA and LL-BCVA. Within a fovea-centered 1-mm circle, the percentage of choriocapillaris flow deficits (CC FD%), drusen volume, optical attenuation coefficient (OAC) elevation volume, and outer retinal layer (ORL) thickness were assessed.

RESULTS

In all 90 eyes (30 normal eyes; 31 drusen-only eyes; 29 non-foveal GA eyes), significant correlations were found between the central CC FD% and PL-BCVA (r = -0.393, P < .001), LL-BCVA (r = -0.534, P < .001), and the LLVAD (r = 0.439, P < .001). Central cube root (cubrt) drusen volume, cubrt OAC elevation volume, and ORL thickness were correlated with PL-BCVA, LL-BCVA, and LLVADs (all P < .05). Stepwise regression models showed that central cubrt OAC elevation volume and ORL thickness were associated with PL-BCVA (R2 = 0.24, P < .05); central CC FD%, cubrt OAC elevation volume, and ORL thickness were associated with LL-BCVA (R2 = 0.44, P < .01); and central CC FD% and ORL thickness were associated with LLVAD (R2 = 0.24, P < .01).

CONCLUSIONS

The significant correlations between central CC FD% and LLVAD support the hypothesis that the ability of LLVAD to predict the growth of GA is mediated through a decrease in macular choriocapillaris perfusion.

A laser-induced mouse model of progressive retinal degeneration with central sparing displays features of parafoveal geographic atrophy

There are no disease-modifying treatments available for geographic atrophy (GA), the advanced form of dry age-related macular degeneration. Current murine models fail to fully recapitulate the features of GA and thus hinder drug discovery. Here we describe a novel mouse model of retinal degeneration with hallmark features of GA. We used an 810 nm laser to create a retinal lesion with central sparing (RLCS), simulating parafoveal atrophy observed in patients with progressive GA. Laser-induced RLCS resulted in progressive GA-like pathology with the development of a confluent atrophic lesion. We demonstrate significant changes to the retinal structure and thickness in the central unaffected retina over a 24-week post-laser period, confirmed by longitudinal optical coherence tomography scans. We further show characteristic features of progressive GA, including a gradual reduction in the thickness of the central, unaffected retina and of total retinal thickness. Histological changes observed in the RLCS correspond to GA pathology, which includes the collapse of the outer nuclear layer, increased numbers of GFAP + , CD11b + and FcγRI + cells, and damage to cone and rod photoreceptors. We demonstrate a laser-induced mouse model of parafoveal GA progression, starting at 2 weeks post-laser and reaching confluence at 24 weeks post-laser. This 24-week time-frame in which GA pathology develops, provides an extended window of opportunity for proof-of-concept evaluation of drugs targeting GA. This time period is an added advantage compared to several existing models of geographic atrophy.

A Protocol to Evaluate and Quantify Retinal Pigmented Epithelium Pathologies in Mouse Models of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a debilitating retinal disorder in aging populations. It is widely believed that dysfunction of the retinal pigmented epithelium (RPE) is a key pathobiological event in AMD. To understand the mechanisms that lead to RPE dysfunction, mouse models can be utilized by researchers. It has been established by previous studies that mice can develop RPE pathologies, some of which are observed in the eyes of individuals diagnosed with AMD. Here, we describe a phenotyping protocol to assess RPE pathologies in mice. This protocol includes the preparation and evaluation of retinal cross-sections using light microscopy and transmission electron microscopy, as well as that of RPE flat mounts by confocal microscopy. We detail the common types of murine RPE pathologies observed by these techniques and ways to quantify them through unbiased methods for statistical testing. As proof of concept, we use this RPE phenotyping protocol to quantify the RPE pathologies observed in mice overexpressing transmembrane protein 135 (Tmem135) and aged wild-type C57BL/6J mice. The main goal of this protocol is to present standard RPE phenotyping methods with unbiased quantitative assessments for scientists using mouse models of AMD.

CORRELATION BETWEEN INFLAMMATORY FOCI REACTIVATION AND ATROPHY GROWTH IN EYES WITH IDIOPATHIC MULTIFOCAL CHOROIDITIS

PURPOSE

To correlate the number of inflammatory reactivations in atrophic foci of multifocal choroiditis (MFC) with their growth rate over a 4-year span.

METHODS

Comparative case series. Optical coherence tomography scans of patients affected by MFC were reviewed to identify reactivations within or at the margin of atrophic MFC foci. The area of selected lesions was semiautomatically delineated on fundus autofluorescence images and recorded at yearly intervals for a total follow-up of 4 years. The main outcome was the difference in annual square-root transformed area growth rate between lesions that reactivated and lesions that did not.

RESULTS

Sixty-six foci of 30 eyes of 24 patients were included. All MFC foci enlarged over time, but the annual growth rate was more than double in lesions that reactivated compared with those that did not (mean [SD], 0.051 [0.035] vs. 0.021 [0.015] mm/year, P < 0.001), despite starting from comparable baseline areas. For each additional inflammatory reactivation, the annual growth rate increased by more than 20% (+0.009 mm/year, 95% CI [0.006, 0.012], P < 0.001).

CONCLUSION

Increasing number of reactivations of atrophic foci led to proportional increments in their growth rate, highlighting the need for a tight control of inflammatory relapses in patients affected by MFC.

Modeling inducible neuropathologies of the retina with differential phenotypes in organoids

Neurodegenerative diseases remain incompletely understood and therapies are needed. Stem cell-derived organoid models facilitate fundamental and translational medicine research. However, to which extent differential neuronal and glial pathologic processes can be reproduced in current systems is still unclear. Here, we tested 16 different chemical, physical, and cell functional manipulations in mouse retina organoids to further explore this. Some of the treatments induce differential phenotypes, indicating that organoids are competent to reproduce distinct pathologic processes. Notably, mouse retina organoids even reproduce a complex pathology phenotype with combined photoreceptor neurodegeneration and glial pathologies upon combined (not single) application of HBEGF and TNF, two factors previously associated with neurodegenerative diseases. Pharmacological inhibitors for MAPK signaling completely prevent photoreceptor and glial pathologies, while inhibitors for Rho/ROCK, NFkB, and CDK4 differentially affect them. In conclusion, mouse retina organoids facilitate reproduction of distinct and complex pathologies, mechanistic access, insights for further organoid optimization, and modeling of differential phenotypes for future applications in fundamental and translational medicine research.

Extracting spacing-derived estimates of rod density in healthy retinae

Quantification of the rod photoreceptor mosaic using adaptive optics scanning light ophthalmoscopy (AOSLO) remains challenging. Here we demonstrate a method for deriving estimates of rod density and rod:cone ratio based on measures of rod spacing, cone numerosity, and cone inner segment area. Twenty-two AOSLO images with complete rod visualization were used to validate this spacing-derived method for estimating density. The method was then used to estimate rod metrics in an additional 105 images without complete rod visualization. The spacing-derived rod mosaic metrics were comparable to published data from histology. This method could be leveraged to develop large normative databases of rod mosaic metrics, though limitations persist with intergrader variability in assessing cone area and numerosity.

Does the Outer Retinal Thickness Around Geographic Atrophy Represent Another Clinical Biomarker for Predicting Growth?

PURPOSE

To determine whether the outer retinal layer (ORL) thickness around geographic atrophy (GA) could serve as a clinical biomarker to predict the annual enlargement rate (ER) of GA.

DESIGN

Retrospective analysis of a prospective, observational case series.

METHODS

Eyes with GA were imaged with a swept-source OCT 6 × 6 mm scan pattern. GA lesions were measured from customized en face OCT images and the annual ERs were calculated. The ORL was defined and segmented from the inner boundary of outer plexiform layer (OPL) to the inner boundary of retinal pigment epithelium (RPE) layer. The ORL thickness was measured at different subregions around GA.

RESULTS

A total of 38 eyes from 27 participants were included. The same eyes were used for the choriocapillaris (CC) flow deficit (FD) analysis and the RPE to the Bruch membrane (RPE-BM) distance measurements. A negative correlation was observed between the ORL thickness and the GA growth. The ORL thickness in a 300-μm rim around GA showed the strongest correlation with the GA growth (r = -0.457, P = .004). No correlations were found between the ORL thickness and the CC FDs; however, a significant correlation was found between the ORL thickness and the RPE-BM distances around GA (r = -0.398, P = .013).

CONCLUSIONS

ORL thickness showed a significant negative correlation with annual GA growth, but also showed a significant correlation with the RPE-BM distances, suggesting that they were dependently correlated with GA growth. This finding suggests that the loss of photoreceptors was associated with the formation of basal laminar deposits around GA.

Association of complement C3 inhibitor pegcetacoplan with reduced photoreceptor degeneration beyond areas of geographic atrophy

Preservation of photoreceptors beyond areas of retinal pigment epithelium atrophy is a critical treatment goal in eyes with geographic atrophy (GA) to prevent vision loss. Thus, we assessed the association of treatment with the complement C3 inhibitor pegcetacoplan with optical coherence tomography (OCT)-based photoreceptor laminae thicknesses in this post hoc analysis of the FILLY trial (NCT02503332). Retinal layers in OCT were segmented using a deep-learning-based pipeline and extracted along evenly spaced contour-lines surrounding areas of GA. The primary outcome measure was change from baseline in (standardized) outer nuclear layer (ONL) thickness at the 5.16°-contour-line at month 12. Participants treated with pegcetacoplan monthly had a thicker ONL along the 5.16° contour-line compared to the pooled sham arm (mean difference [95% CI] + 0.29 z-score units [0.16, 0.42], P < 0.001). The same was evident for eyes treated with pegcetacoplan every other month (+ 0.26 z-score units [0.13, 0.4], P < 0.001). Additionally, eyes treated with pegcetacoplan exhibited a thicker photoreceptor inner segment layer along the 5.16°-contour-line at month 12. These findings suggest that pegcetacoplan could slow GA progression and lead to reduced thinning of photoreceptor layers beyond the GA boundary. Future trials in earlier disease stages, i.e., intermediate AMD, aiming to slow photoreceptor degeneration warrant consideration.

HBEGF-TNF induce a complex outer retinal pathology with photoreceptor cell extrusion in human organoids

Human organoids could facilitate research of complex and currently incurable neuropathologies, such as age-related macular degeneration (AMD) which causes blindness. Here, we establish a human retinal organoid system reproducing several parameters of the human retina, including some within the macula, to model a complex combination of photoreceptor and glial pathologies. We show that combined application of TNF and HBEGF, factors associated with neuropathologies, is sufficient to induce photoreceptor degeneration, glial pathologies, dyslamination, and scar formation: These develop simultaneously and progressively as one complex phenotype. Histologic, transcriptome, live-imaging, and mechanistic studies reveal a previously unknown pathomechanism: Photoreceptor neurodegeneration via cell extrusion. This could be relevant for aging, AMD, and some inherited diseases. Pharmacological inhibitors of the mechanosensor PIEZO1, MAPK, and actomyosin each avert pathogenesis; a PIEZO1 activator induces photoreceptor extrusion. Our model offers mechanistic insights, hypotheses for neuropathologies, and it could be used to develop therapies to prevent vision loss or to regenerate the retina in patients suffering from AMD and other diseases.

Advanced Retina Implants

PURPOSE

To discuss the role of advanced retinal implants in retinitis pigmentosa and age-related macular degeneration.

DESIGN

Presented by Mark S. Humayun as the Charles Schepen's Lecture on the Retina Subspecialty Day of the American Academy of Ophthalmology in 2021.

PARTICIPANTS

The details of subjects, participants, and controls are provided in the references pertaining to each study.

METHODS

Review of published literature and clinical trials.

MAIN OUTCOME MEASURES

Visual and anatomic outcomes from retinal implants.

RESULTS

Retinal implants have been researched over the past few decades, and some have been advanced into the clinic. Two types of implants-bioelectronic and stem cell-based-have shown promising results in restoring some level of vision in patients with inherited retinal degeneration and geographic atrophy. These implants differ in their constructions, locations of implantation, and safety profiles. The results from some of these retinal implants have shown signs of efficacy, and 1 retinal implant, the Argus II, has been approved by the United States Food and Drug Administration.

CONCLUSIONS

Careful consideration of the design of the implant and associated surgical techniques are necessary to obtain a stable and effective long-term interface between the implant and the retina.

Prediction of visual function from automatically quantified optical coherence tomography biomarkers in patients with geographic atrophy using machine learning

Geographic atrophy (GA) is a vision-threatening manifestation of age-related macular degeneration (AMD), one of the leading causes of blindness globally. Objective, rapid, reliable, and scalable quantification of GA from optical coherence tomography (OCT) retinal scans is necessary for disease monitoring, prognostic research, and clinical endpoints for therapy development. Such automatically quantified biomarkers on OCT are likely to further elucidate structure-function correlation in GA and thus the pathophysiological mechanisms of disease development and progression. In this work, we aimed to predict visual function with machine-learning applied to automatically acquired quantitative imaging biomarkers in GA. A post-hoc analysis of data from a clinical trial and routine clinical care was conducted. A deep-learning automated segmentation model was applied on OCT scans from 476 eyes (325 patients) with GA. A separate machine learning prediction model (Random Forest) used the resultant quantitative OCT (qOCT) biomarkers to predict cross-sectional visual acuity under standard (VA) and low luminance (LLVA). The primary outcome was regression coefficient (r2) and mean absolute error (MAE) for cross-sectional VA and LLVA in Early Treatment Diabetic Retinopathy Study (ETDRS) letters. OCT parameters were predictive of VA (r2 0.40 MAE 11.7 ETDRS letters) and LLVA (r2 0.25 MAE 12.1). Normalised random forest feature importance, as a measure of the predictive value of the three constituent features of GA; retinal pigment epithelium (RPE)-loss, photoreceptor degeneration (PDR), hypertransmission and their locations, was reported both on voxel-level heatmaps and ETDRS-grid subfields. The foveal region (46.5%) and RPE-loss (31.1%) had greatest predictive importance for VA. For LLVA, however, non-foveal regions (74.5%) and PDR (38.9%) were most important. In conclusion, automated qOCT biomarkers demonstrate predictive significance for VA and LLVA in GA. LLVA is itself predictive of GA progression, implying that the predictive qOCT biomarkers provided by our model are also prognostic.

The role of dual antiplatelets in geographic atrophy secondary to non-neovascular aged-related macular degeneration

Background

To evaluate the effects of dual antiplatelets on progression of geographic atrophy (GA) secondary to age-related macular degeneration (AMD), and to determine additional factors predicting rapid GA growth.

Material and Methods

In this retrospective cohort study, patients with unifocal GA were consecutively enrolled (one eye per patient) from 2018 to 2021. The patients were categorized as 1. those receiving dual antiplatelet therapy containing a daily dose of 75 mg clopidogrel plus 81 mg aspirin (DAPT group), and 2. those not receiving DAPT (control group). Areas of GA, based on red-filtered fundus autofluorescence, were measured at baseline, and at 3, 6, and 12 months. The primary outcome was absolute 12-month changes in the square root (SQRT) area.

Results

One eye in each group developed neovascular AMD and was excluded from the analysis. The DAPT (24 eyes) and control (22 eyes) groups had comparable age and baseline SQRT area (1.2 ± 0.27 and 1.8 ± 0.41 mm, respectively; p adjusted for age = 0.23). At 12 months, after controlling for age and the presence of soft drusen or reticular pseudodrusen, patients receiving DAPT had fewer changes in the SQRT area than that of the control group (0.097 vs. 0.17 mm; p = 0.02). The presence of drusen significantly predicted increased GA growth and choroidal thickness reduction.

Conclusions

Routine uses of dual antiplatelets were associated with decelerating GA growth. Drusen-associated GA may represent a generalized form of choroidal vascular alterations.

Neuroprotection for Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. Early to intermediate AMD is characterized by the accumulation of lipid- and protein-rich drusen. Late stages of the disease are characterized by the development of choroidal neovascularization, termed "exudative" or "neovascular AMD," or retinal pigment epithelium (RPE) cell and photoreceptor death, termed "geographic atrophy" (GA) in advanced nonexudative AMD. Although we have effective treatments for exudative AMD in the form of anti-VEGF agents, they have no role for patients with GA. Neuroprotection strategies have emerged as a possible way to slow photoreceptor degeneration and vision loss in patients with GA. These approaches include reduction of oxidative stress, modulation of the visual cycle, reduction of toxic molecules, inhibition of pathologic protein activity, prevention of cellular apoptosis or programmed necrosis (necroptosis), inhibition of inflammation, direct activation of neurotrophic factors, delivery of umbilical tissue-derived cells, and RPE replacement. Despite active investigation in this area and significant promise based on preclinical studies, many clinical studies have not yielded successful results. We discuss selected past and current neuroprotection trials for AMD, highlight the lessons learned from these past studies, and discuss our perspective regarding remaining questions that must be answered before neuroprotection can be successfully applied in the field of AMD research.

New Prospects for Retinal Pigment Epithelium Transplantation

ABSTRACT

Retinal pigment epithelium (RPE) transplants rescue photoreceptors in selected animal models of retinal degenerative disease. Early clinical studies of RPE transplants as treatment for age-related macular degeneration (AMD) included autologous and allogeneic transplants of RPE suspensions and RPE sheets for atrophic and neovascular complications of AMD. Subsequent studies explored autologous RPE-Bruch membrane-choroid transplants in patients with neovascular AMD with occasional marked visual benefit, which establishes a rationale for RPE transplants in late-stage AMD. More recent work has involved transplantation of autologous and allogeneic stem cell-derived RPE for patients with AMD and those with Stargardt disease. These early-stage clinical trials have employed RPE suspensions and RPE monolayers on biocompatible scaffolds. Safety has been well documented, but evidence of efficacy is variable. Current research involves development of better scaffolds, improved modulation of immune surveillance, and modification of the extracellular milieu to improve RPE survival and integration with host retina.

A High Fat "Western-style" Diet Induces AMD-Like Features in Wildtype Mice

Scope

The intake of a “Western‐style” diet rich in fats is linked with developing retinopathies including age‐related macular degeneration (AMD). Wildtype mice are given a high fat diet (HFD) to determine how unhealthy foods can bring about retinal degeneration.

Methods and results

Following weaning, female C57BL/6 mice are maintained on standard chow (7% kcal fat, n = 29) or a HFD (45% kcal fat, n = 27) for 12 months. Animals were sacrificed following electroretinography (ERG) and their eyes analyzed by histology, confocal immunofluorescence, and transmission electron microscopy. HFD mice become obese, but showed normal retinal function compared to chow‐fed controls. However, diminished β3tubulin labeling of retinal cross‐sections indicated fewer/damaged neuronal processes in the inner plexiform layer. AMD‐linked proteins clusterin and TIMP3 accumulated in the retinal pigment epithelium (RPE) and Bruch's membrane (BrM). Neutral lipids also deposited in the outer retinae of HFD mice. Ultrastructural analysis revealed disorganized photoreceptor outer segments, collapsed/misaligned RPE microvilli, vacuoles, convoluted basolateral RPE infolds and BrM changes. Basal laminar‐like deposits were also present alongside abnormal choroidal endothelial cells.

Conclusions

We show that prolonged exposure to an unhealthy “Western‐style” diet alone can recapitulate early‐intermediate AMD‐like features in wildtype mice, highlighting the importance of diet and nutrition in the etiology of sight‐loss.

Baseline Sattler Layer-Choriocapillaris complex Thickness cutoffs associated with age-related macular degeneration progression

PURPOSE

This study aims to assess the relationship between choroidal overall and sublayer thickness and AMD stage progression.

METHODS

A prospective, observational case series was performed. 262 eyes of 262 patients with different stages of AMD were imaged by Optical Coherence Tomography (OCT). AMD stage, choroidal thickness (CT), Sattler layer-choriocapillaris complex thickness (SLCCT) and Haller layer thickness (HLT) were determined at the baseline visit, at a 1-year follow-up visit, at a 2-year follow up visit and at a final visit (performed after a mean of 5 ± 1 years from the baseline visit).

RESULTS

Baseline AMD stages were distributed as follows: early AMD (30 eyes; 12%), intermediate AMD (97 eyes; 39%) and late AMD (126 eyes; 49%). At the final follow-up, AMD stages were so distributed: early AMD (14 eyes; 6%), intermediate AMD (83 eyes; 33%) and late AMD (156 eyes; 61%). Each group showed a statistically significant decrease in CT values over the entire follow-up (p <0.001) and SLCCT reduction was associated with AMD progression (p <0.001). Moreover, SLCCT quantitative cutoffs <20.50 µm and <10.5 µm were associated with a moderate and high probability of AMD progression, respectively, and SLCCT quantitative cutoffs <18.50 µm and <8.50 µm implied a moderate and high probability of macular neovascularization (MNV) onset, respectively.

CONCLUSIONS

Progressive choroidal impairment contributes to AMD progression. Among choroidal layers, a reduced SLCCT is a promising biomarker of disease worsening and its quantitative evaluation could help to identify patients at higher risk of stage advancement.

Comparing Accuracies of Length-Type Geographic Atrophy Growth Rate Metrics Using Atrophy-Front Growth Modeling

Purpose

To compare the accuracies of the previously proposed square-root-transformed and perimeter-adjusted metrics for estimating length-type geographic atrophy (GA) growth rates.

Design

Cross-sectional and simulation-based study.

Participants

Thirty-eight eyes with GA from 27 patients.

Methods

We used a previously developed atrophy-front growth model to provide analytical and numerical evaluations of the square-root-transformed and perimeter-adjusted growth rate metrics on simulated and semisimulated GA growth data.

Main Outcome Measures

Comparison of the accuracies of the square-root-transformed and perimeter-adjusted metrics on simulated and semisimulated GA growth data.

Results

Analytical and numerical evaluations showed that the accuracy of the perimeter-adjusted metric is affected minimally by baseline lesion area, focality, and circularity over a wide range of GA growth rates. Average absolute errors of the perimeter-adjusted metric were approximately 20 times lower than those of the square-root-transformed metrics, per evaluation on a semisimulated dataset with growth rate characteristics matching clinically observed data.

Conclusions

Length-type growth rates have an intuitive, biophysical interpretation that is independent of lesion geometry, which supports their use in clinical trials of GA therapeutics. Taken in the context of prior studies, our analyses suggest that length-type GA growth rates should be measured using the perimeter-adjusted metric, rather than square-root-transformed metrics.

Optical Coherence Tomography Measurements of the Retinal Pigment Epithelium to Bruch Membrane Thickness Around Geographic Atrophy Correlate With Growth

PURPOSE

The retinal pigment epithelium (RPE) to Bruch membrane (BM) distance around geographic atrophy (GA) was measured using an optical attenuation coefficient (OAC) algorithm to determine whether this measurement could serve as a clinical biomarker to predict the annual square root enlargement rate (ER) of GA.

DESIGN

A retrospective analysis of a prospective, observational case series.

METHODS

Eyes with GA secondary to age-related macular degeneration (AMD) were imaged with swept-source OCT (SS-OCT) using a 6 × 6-mm scan pattern. GA lesions were identified and measured using customized en face OCT images, and GA annual square root ERs were calculated. At baseline, the OACs were calculated from OCT datasets to generate customized en face OAC images for GA visualization. RPE-BM distances were measured using OAC data from different subregions around the GA.

RESULTS

A total of 38 eyes from 27 patients were included in this study. Measured RPE-BM distances were the highest in the region closest to GA. The RPE-BM distances immediately around the GA were significantly correlated with GA annual square root ERs (r = 0.595, P < .001 for a 0- to 300-µm rim around the GA). No correlations were found between RPE-BM distances and previously published choriocapillaris (CC) flow deficits in any subregions.

CONCLUSIONS

RPE-BM distances from regions around the GA significantly correlate with the annual ERs of GA. These results suggest that an abnormally thickened RPE/BM complex contributes to GA growth and that this effect is independent of CC perfusion deficits.

Automatic geographic atrophy segmentation using optical attenuation in OCT scans with deep learning

A deep learning algorithm was developed to automatically identify, segment, and quantify geographic atrophy (GA) based on optical attenuation coefficients (OACs) calculated from optical coherence tomography (OCT) datasets. Normal eyes and eyes with GA secondary to age-related macular degeneration were imaged with swept-source OCT using 6 × 6 mm scanning patterns. OACs calculated from OCT scans were used to generate customized composite en face OAC images. GA lesions were identified and measured using customized en face sub-retinal pigment epithelium (subRPE) OCT images. Two deep learning models with the same U-Net architecture were trained using OAC images and subRPE OCT images. Model performance was evaluated using DICE similarity coefficients (DSCs). The GA areas were calculated and compared with manual segmentations using Pearson's correlation and Bland-Altman plots. In total, 80 GA eyes and 60 normal eyes were included in this study, out of which, 16 GA eyes and 12 normal eyes were used to test the models. Both models identified GA with 100% sensitivity and specificity on the subject level. With the GA eyes, the model trained with OAC images achieved significantly higher DSCs, stronger correlation to manual results and smaller mean bias than the model trained with subRPE OCT images (0.940 ± 0.032 vs 0.889 ± 0.056, p = 0.03, paired t-test, r = 0.995 vs r = 0.959, mean bias = 0.011 mm vs mean bias = 0.117 mm). In summary, the proposed deep learning model using composite OAC images effectively and accurately identified, segmented, and quantified GA using OCT scans.

Volumetric directional optical coherence tomography

Photoreceptor loss and resultant thinning of the outer nuclear layer (ONL) is an important pathological feature of retinal degenerations and may serve as a useful imaging biomarker for age-related macular degeneration. However, the demarcation between the ONL and the adjacent Henle's fiber layer (HFL) is difficult to visualize with standard optical coherence tomography (OCT). A dedicated OCT system that can precisely control and continuously and synchronously update the imaging beam entry points during scanning has not been realized yet. In this paper, we introduce a novel imaging technology, Volumetric Directional OCT (VD-OCT), which can dynamically adjust the incident beam on the pupil without manual adjustment during a volumetric OCT scan. We also implement a customized spoke-circular scanning pattern to observe the appearance of HFL with sufficient optical contrast in continuous cross-sectional scans through the entire volume. The application of VD-OCT for retinal imaging to exploit directional reflectivity properties of tissue layers has the potential to allow for early identification of retinal diseases.

Choroidal caverns in pachychoroid neovasculopathy

Background. Choroid plays an important role in the pathogenesis of retinal pathology. Choroidal cavern, a recently identifi ed fi nding of optical coherent tomography (OCT), has been described in some degenerative and atrophic forms of retinal pathology. In the literature, there are only a few studies of choroidal cavers in pachychoroid neovasculopathy, newly described form of age related macular degeneration.The aim: to perform a detailed analysis of choroidal structure on OCT scans of patients with pachychoroid neovasculopathy and to reveal the frequency of choroidal caverns identifi cation.Material and methods. The data of 30 patients (30 eyes) aged 64.4 ± 5.6 years with pachychoroid neovascularization were retrospectively analyzed. The patients underwent spectral OCT and OCT-angiography (OCTA) using a Spectralis device (Heidelberg Engineering, Germany). The protocol was “Posterior Pole”, consisting of 61 scans. To assess the structure of the choroid, an enhanced image depth (EDI) module was used. OCT angiography was performed with a scan area of 6 × 6 mm. These methods were compared to identify choroidal caverns.Results. On OCT subretinal type 1 neovascularization was revealed as a fl at detachment of the pigment epithelium and visualization of blood flow on OCTA in the lesion as angled vessels (21 eyes) or a seafan (9 eyes). On OCT-EDI scans, there was diffuse or local choroidal thickening of choroid with an increase in the vessels of the Haller’s layer and thinning of the choriocapillaries. Choroidal caverns appeared on OCT and en-face OCT as areas with low optical density, round or irregular, located in different layers of the chorioid, without hyperrefl ective boundaries. A typical sign of choroidal cavern is the tail of hypertransmission after the cavern toward the sclera. Choroidal caverns were found in 4 of 30 eyes (13.3 %) and were located both near the choroidal neovascularization lesion and beyond this area.Conclusion. The prevalence of choroidal cavities, a new choroidal biomarker, in pachychoroid neovasculopathy was 13.3 %. Identification of these changes is possible with the use of modern diagnostic techniques (OCT-EDI, OCTA and en-face OCT) that allow visualization the state of the choroid. The prognostic signifi cance of choroidal cavities requires further study.

Dietary Antioxidants in Age-Related Macular Degeneration and Glaucoma

Age-related macular degeneration (AMD) and glaucoma are ophthalmic neurodegenerative diseases responsible for irreversible vision loss in the world population. Only a few therapies can be used to slow down the progression of these diseases and there are no available treatment strategies for reversing the degeneration of the neural retina. In AMD, the pathological process causes the malfunction and damage of the retinal pigmented epithelium and photoreceptors in the macula. In glaucoma, damage of the retinal ganglion cells and their axons is observed and treatment strategies are limited to intraocular pressure lowering. Therefore, other prophylactic and/or therapeutic methods are needed. Oxidative stress is involved in the neurodegenerative process accompanying both AMD and glaucoma; therefore, the use of antioxidant agents would clearly be beneficial, which is supported by the decreased prevalence and progression of AMD in patients adherent to a diet naturally rich in antioxidants. Dietary antioxidants are easily available and their use is based on the natural route of administration. Many preclinical studies both in vitro and using animal models of retinal degeneration showed the efficacy of dietary antioxidants, which was further proved in clinical trials. Resveratrol is beneficial both in AMD and glaucoma animal models, but confirmed only among AMD patients. For AMD, carotenoids and omega-3 fatty acids were also proved to be sufficient in preventing neurodegeneration. For glaucoma, coenzyme Q10 and alpha-lipoic acid showed efficacy for decreasing retinal ganglion cell loss and inhibiting the accompanying destructive processes. Interestingly, the benefits of vitamins, especially vitamin E was not confirmed, neither in preclinical nor in clinical studies.

Localized Structural and Functional Deficits in a Nonhuman Primate Model of Outer Retinal Atrophy

Purpose

Cell-based therapy development for geographic atrophy (GA) in age-related macular degeneration (AMD) is hampered by the paucity of models of localized photoreceptor and retinal pigment epithelium (RPE) degeneration. We aimed to characterize the structural and functional deficits in a laser-induced nonhuman primate model, including an analysis of the choroid.

Methods

Macular laser photocoagulation was applied in four macaques. Fundus photography, optical coherence tomography (OCT), dye angiography, and OCT-angiography were conducted over 4.5 months, with histological correlation. Longitudinal changes in spatially resolved macular dysfunction were measured using multifocal electroretinography (MFERG).

Results

Lesion features, depending on laser settings, included photoreceptor layer degeneration, inner retinal sparing, skip lesions, RPE elevation, and neovascularization. The intralesional choroid was degenerated. The normalized mean MFERG amplitude within lesions was consistently lower than control regions (0.94 ± 0.35 vs. 1.10 ± 0.27, P = 0.032 at month 1, 0.67 ± 0.22 vs. 0.83 ± 0.15, P = 0.0002 at month 2, and 0.97 ± 0.31 vs. 1.20 ± 0.21, P < 0.0001 at month 3.5). The intertest variation of mean MFERG amplitudes in rings 1 to 5 ranged from 13.0% to 26.0% in normal eyes.

Conclusions

Laser application in this model caused localized outer retinal, RPE, and choriocapillaris loss. Localized dysfunction was apparent by MFERG in the first month after lesion induction. Correlative structure-function testing may be useful for research on the functional effects of stem cell-based therapy for GA. MFERG amplitude data should be interpreted in the context of relatively high intertest variability of the rings that correspond to the central macula. Sustained choroidal insufficiency may limit long-term subretinal graft viability in this model.

One-Year Follow-Up in a Phase 1/2a Clinical Trial of an Allogeneic RPE Cell Bioengineered Implant for Advanced Dry Age-Related Macular Degeneration

Purpose

To report 1-year follow-up of a phase 1/2a clinical trial testing a composite subretinal implant having polarized human embryonic stem cell (hESC)-derived retinal pigment epithelium (RPE) cells on an ultrathin parylene substrate in subjects with advanced non-neovascular age-related macular degeneration (NNAMD)

Methods

The phase 1/2a clinical trial included 16 subjects in two cohorts. The main endpoint was safety assessed at 365 days using ophthalmic and systemic exams. Pseudophakic subjects with geographic atrophy (GA) and severe vision loss were eligible. Low-dose tacrolimus immunosuppression was utilized for 68 days in the peri-implantation period. The implant was delivered to the worst seeing eye with a custom subretinal insertion device in an outpatient setting. A data safety monitoring committee reviewed all results.

Results

The treated eyes of all subjects were legally blind with a baseline best-corrected visual acuity (BCVA) of ≤ 20/200. There were no unexpected serious adverse events. Four subjects in cohort 1 had serious ocular adverse events, including retinal hemorrhage, edema, focal retinal detachment, or RPE detachment, which was mitigated in cohort 2 using improved hemostasis during surgery. Although this study was not powered to assess efficacy, treated eyes from four subjects showed an increased BCVA of >5 letters (6–13 letters). A larger proportion of treated eyes experienced a >5-letter gain when compared with the untreated eye (27% vs. 7%; P = not significant) and a larger proportion of nonimplanted eyes demonstrated a >5-letter loss (47% vs. 33%; P = not significant).

Conclusions

Outpatient delivery of the implant can be performed routinely. At 1 year, the implant is safe and well tolerated in subjects with advanced dry AMD.

Translational Relevance

This work describes the first clinical trial, to our knowledge, of a novel implant for advanced dry AMD.

Targeting complement components C3 and C5 for the retina: Key concepts and lingering questions

Age-related macular degeneration (AMD) remains a major cause of legal blindness, and treatment for the geographic atrophy form of AMD is a significant unmet need. Dysregulation of the complement cascade is thought to be instrumental for AMD pathophysiology. In particular, C3 and C5 are pivotal components of the complement cascade and have become leading therapeutic targets for AMD. In this article, we discuss C3 and C5 in detail, including their roles in AMD, biochemical and structural aspects, locations of expression, and the functions of C3 and C5 fragments. Further, the article critically reviews developing therapeutics aimed at C3 and C5, underscoring the potential effects of broad inhibition of complement at the level of C3 versus more specific inhibition at C5. The relationships of complement biology to the inflammasome and microglia/macrophage activity are highlighted. Concepts of C3 and C5 biology will be emphasized, while we point out questions that need to be settled and directions for future investigations.

Growth Modeling for Quantitative, Spatially Resolved Geographic Atrophy Lesion Kinetics

Purpose

To demonstrate the applicability of a growth modeling framework for quantifying spatial variations in geographic atrophy (GA) lesion kinetics.

Methods

Thirty-eight eyes from 27 patients with GA secondary to age-related macular degeneration were imaged with a commercial swept source optical coherence tomography instrument at two visits separated by 1 year. Local GA growth rates were computed at 6-µm intervals along each lesion margin using a previously described growth model. Corresponding margin eccentricities, margin angles, and growth angles were also computed. The average GA growth rates conditioned on margin eccentricity, margin angle, growth angle, and fundus position were estimated via kernel regression.

Results

A total of 88,356 GA margin points were analyzed. The average GA growth rates exhibited a hill-shaped dependency on eccentricity, being highest in the 0.5 mm to 1.6 mm range and lower on either side of that range. Average growth rates were also found to be higher for growth trajectories oriented away from (smaller growth angle), rather than toward (larger growth angle), the foveal center. The dependency of average growth rate on margin angle was less pronounced, although lesion segments in the superior and nasal aspects tended to grow faster.

Conclusions

Our proposed growth modeling framework seems to be well-suited for generating accurate, spatially resolved GA growth rate atlases and should be confirmed on larger datasets.

Translational Relevance

Our proposed growth modeling framework may enable more accurate measurements of spatial variations in GA growth rates.

Correlations Between Choriocapillaris and Choroidal Measurements and the Growth of Geographic Atrophy Using Swept Source OCT Imaging

PURPOSE

Correlations among enlargement rates (ERs) of geographic atrophy (GA) and choriocapillaris (CC) flow deficits (FDs), mean choroidal thickness (MCT), and choroidal vascularity index (CVI) were investigated using swept source-optical coherence tomography (SS-OCT) in age-related macular degeneration (AMD).

DESIGN

A retrospective review of prospective, observational case series.

METHODS

Eyes with GA from AMD were imaged with SS-OCT using 6 × 6-mm scan pattern. GA lesions were identified and measured using customized en face structural images, and annual square root ERs of GA were calculated. At baseline, choriocapillaris FDs from different regions outside the GA were measured, and MCT and CVI from the entire scan area were measured. All measurements were performed using previously published and validated algorithms.

RESULTS

A total of 38 eyes from 27 patients were included. The CC FDs within each region around GA lesions were highly correlated with ERs of GA (all P < .005). CVI inside the GA region was correlated with the ERs (P = .03), whereas other choroidal measurements had no significant correlation with the ERs of GA (P > .06).

CONCLUSIONS

Statistically significant correlations were found between the ERs of GA and CC percentage of FD (FD%) from the entire scan region outside the GA and not just the region immediately adjacent to the GA. These results suggest that abnormal CC perfusion throughout the macula contributes to disease progression in eyes with GA. CVI inside the GA region could also be a potential indicator for the growth of GA.

Choroidal neovascularization secondary to pathological myopia-macular Bruch membrane defects as prognostic factor to anti-VEGF treatment

PURPOSE

To evaluate the prevalence and visual outcomes of macular Bruch membrane (BM) defects in patients treated with anti-vascular endothelial growth factors (VEGF) for choroidal neovascularization secondary to pathological myopia (mCNV).

METHODS

Single-center retrospective observational case series of 68 eyes from 62 patients with mCNV treated with one anti-VEGF injection followed by a pro re nata (1 + PRN) regimen. A minimum follow-up of 6 months was defined. Chorioretinal atrophy was assessed by fundus examination, fluorescein angiography, and SD-OCT.

RESULTS

Median follow-up was 28.5 (range 6-89) months with a median number of 5 anti-VEGF injections. At baseline, 27.9% of eyes had macular BM defects increasing to 36.8% during follow-up (p<0.001). Eyes without macular BM defects at the baseline had higher BCVA at the last observation than patients with BM defects (p=0.003). An increase of 5 or more ETDRS letters was more frequent in eyes without BM defects (p=0.001). At the end of follow-up, mCNV-related macular atrophy was present in 44.1%; out of which, 83.3% presented macular BM defects (p<0.001). Eyes with mCNV-related macular atrophy without BM defects had a significant increase of best-corrected visual acuity compared with eyes with mCNV-related macular atrophy and BM defect (p=0.002).

CONCLUSIONS

Macular Bruch membrane defects are often seen in mCNV and have a significant impact in visual acuity and prognosis. Eyes with macular BM defects have a poorer response and worse visual outcomes after anti-VEGF therapy.

Optical Coherence Tomography Angiography of the Choriocapillaris in Age-Related Macular Degeneration

The advent of optical coherence tomography angiography (OCTA) has allowed for remarkable advancements in our understanding of the role of the choriocapillaris in age-related macular degeneration (AMD). As a relatively new imaging modality, techniques to analyze and quantify choriocapillaris images are still evolving. Quantification of the choriocapillaris requires careful consideration of many factors, including the type of OCTA device, segmentation of the choriocapillaris slab, image processing techniques, and thresholding method. OCTA imaging shows that the choriocapillaris is impaired in intermediate non-neovascular AMD, and the severity of impairment may predict the advancement of disease. In advanced atrophic AMD, the choriocapillaris is severely impaired underneath the area of geographic atrophy, and the level of impairment surrounding the lesion predicts the rate of atrophy enlargement. Macular neovascularization can be readily identified and classified using OCTA, but it is still unclear if neovascularization features with OCTA can predict the lesion’s level of activity. The choriocapillaris surrounding macular neovascularization is impaired while the more peripheral choriocapillaris is spared, implying that choriocapillaris disruption may drive neovascularization growth. With continued innovation in OCTA image acquisition and analysis methods, advancement in clinical applications and pathophysiologic discoveries in AMD are set to follow.

Surgical Transplantation of Human RPE Stem Cell-Derived RPE Monolayers into Non-Human Primates with Immunosuppression

Recent trials of retinal pigment epithelium (RPE) transplantation for the treatment of disorders such as age-related macular degeneration have been promising. However, limitations of existing strategies include the uncertain survival of RPE cells delivered by cell suspension and the inherent risk of uncontrolled cell proliferation in the vitreous cavity. Human RPE stem cell-derived RPE (hRPESC-RPE) transplantation can rescue vision in a rat model of retinal dystrophy and survive in the rabbit retina for at least 1 month. The present study placed hRPESC-RPE monolayers under the macula of a non-human primate model for 3 months. The transplant was able to recover in vivo and maintained healthy photoreceptors. Importantly, there was no evidence that subretinally transplanted monolayers underwent an epithelial-mesenchymal transition. Neither gliosis in adjacent retina nor epiretinal membranes were observed. These findings suggest that hRPESC-RPE monolayers are safe and may be a useful source for RPE cell replacement therapy.

•

hRPESC-RPE monolayer transplanted under macula of non-human primates

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Transplanted hRPESC-RPE recovers in vivo and maintains healthy photoreceptors

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Transplanted cells did not undergo epithelial-mesenchymal transition

•

Gliosis was not observed in adjacent retina for up to at least 3 months

Bruch's Membrane and the Choroid in Age-Related Macular Degeneration

A healthy choroidal vasculature is necessary to support the retinal pigment epithelium (RPE) and photoreceptors, because there is a mutualistic symbiotic relationship between the components of the photoreceptor/retinal pigment epithelium (RPE)/Bruch's membrane (BrMb)/choriocapillaris (CC) complex. This relationship is compromised in age-related macular degeneration (AMD) by the dysfunction or death of the choroidal vasculature. This chapter will provide a basic description of the human Bruch's membrane and choroidal anatomy and physiology and how they change in AMD.The choriocapillaris is the lobular, fenestrated capillary system of choroid. It lies immediately posterior to the pentalaminar Bruch's membrane (BrMb). The blood supply for this system is the intermediate blood vessels of Sattler's layer and the large blood vessels in Haller's layer.In geographic atrophy (GA), an advanced form of dry AMD, large confluent drusen form on BrMb, and hyperpigmentation (presumably dysfunction in RPE) appears to be the initial insult. The resorption of these drusen and loss of RPE (hypopigmentation) can be predictive for progression of GA. The death and dysfunction of CC and photoreceptors appear to be secondary events to loss in RPE. The loss of choroidal vasculature may be the initial insult in neovascular AMD (nAMD). We have observed a loss of CC with an intact RPE monolayer in nAMD, by making RPE hypoxic. These hypoxic cells then produce angiogenic substances like vascular endothelial growth factor (VEGF), which stimulate growth of new vessels from CC, resulting in choroidal neovascularization (CNV). Reduction in blood supply to the CC, often stenosis of intermediate and large blood vessels, is associated with CC loss.The polymorphisms in the complement system components are associated with AMD. In addition, the environment of the CC, basement membrane and intercapillary septa, is a proinflammatory milieu with accumulation of proinflammatory molecules like CRP and complement components during AMD. In this toxic milieu, CC die or become dysfunctional even early in AMD. The loss of CC might be a stimulus for drusen formation since the disposal system for retinal debris and exocytosed material from RPE would be limited. Ultimately, the photoreceptors die of lack of nutrients, leakage of serum components from the neovascularization, and scar formation.Therefore, the mutualistic symbiotic relationship of the photoreceptor/RPE/BrMb/CC complex is lost in both forms of AMD. Loss of this functionally integrated relationship results in death and dysfunction of all of the components in the complex.

Age-Related Macular Degeneration: Epidemiology and Clinical Aspects

Age-related macular degeneration (AMD) is a degenerative disease of the human retina affecting individuals over the age of 55 years. This heterogeneous condition arises from a complex interplay between age, genetics, and environmental factors including smoking and diet. It is the leading cause of blindness in industrialized countries. Worldwide, the number of people with AMD is predicted to increase from 196 million in 2020 to 288 million by 2040. By this time, Asia is predicted to have the largest number of people with the disease. Distinct patterns of AMD prevalence and phenotype are seen between geographical areas that are not explained fully by disparities in population structures. AMD is classified into early, intermediate, and late stages. The early and intermediate stages, when visual symptoms are typically absent or mild, are characterized by macular deposits (drusen) and pigmentary abnormalities. Through risk prediction calculators, grading these features helps predict the risk of progression to late AMD. Late AMD is divided into neovascular and atrophic forms, though these can coexist. The defining lesions are macular neovascularization and geographic atrophy, respectively. At this stage, visual symptoms are often severe and irreversible, and can comprise profoundly decreased central vision in both eyes. For these reasons, the condition has major implications for individuals and society, as affected individuals may experience substantially decreased quality of life and independence. Recent advances in retinal imaging have led to the recognition of an expanded set of AMD phenotypes, including reticular pseudodrusen, nonexudative macular neovascularization, and subtypes of atrophy. These developments may lead to refinements in current classification systems.

Progress in developing rodent models of age-related macular degeneration (AMD)

Age-related macular degeneration (AMD) is the leading cause of irreversible central vision loss, typically affecting individuals from mid-life onwards. Its multifactorial aetiology and the lack of any effective treatments has spurred the development of animal models as research and drug discovery tools. Several rodent models have been developed which recapitulate key features of AMD and provide insights into its underlying pathology. These have contributed to making significant progress in understanding the disease and the identification of novel therapeutic targets. However, a major caveat with existing models is that they do not demonstrate the full disease spectrum. In this review, we outline advances in rodent AMD models from the last decade. These models feature various hallmarks associated with AMD, including oxidative stress, hypoxia, immune dysregulation, genetic mutations and environmental risk factors. The review summarises the methods by which each model was created, its pathological characteristics as well as its relation to the disease in humans.

Progression of Geographic Atrophy with Subsequent Exudative Neovascular Disease in Age-Related Macular Degeneration: AREDS2 Report 24

PURPOSE

To examine whether the rate of geographic atrophy (GA) enlargement is influenced by subsequent exudative neovascular age-related macular degeneration (nAMD) and hence, to explore indirectly whether nonexudative nAMD may slow GA enlargement.

DESIGN

Post hoc analysis of a controlled clinical trial cohort.

PARTICIPANTS

Age-Related Eye Disease Study 2 participants 50 to 85 years of age.

METHODS

Baseline and annual stereoscopic color fundus photographs were evaluated for (1) GA presence and area and (2) exudative nAMD presence. Two cohorts were constructed: eyes with GA at study baseline (prevalent cohort) and eyes in which GA developed during follow-up (incident cohort). Mixed-model regression of the square root of GA area was performed according to the presence or absence of subsequent exudative nAMD.

MAIN OUTCOME MEASURES

Change over time in square root of GA area.

RESULTS

Of the 757 eyes in the incident GA cohort, over a mean follow-up of 2.3 years (standard deviation [SD], 1.2 years), 73 eyes (9.6%) demonstrated subsequent exudative nAMD. Geographic atrophy enlargement in these eyes was significantly slower (0.20 mm/year; 95% confidence interval [CI], 0.12-0.28 mm/year) compared with the other 684 eyes in which subsequent exudative nAMD did not develop (0.29 mm/year; 95% CI, 0.27-0.30 mm/year; P = 0.037). Of the 456 eyes in the prevalent GA cohort, over a mean follow-up of 4.1 years (SD, 1.4 years), 63 eyes (13.8%) demonstrated subsequent exudative nAMD. Geographic atrophy enlargement in these eyes was similar (0.31 mm/year; 95% CI, 0.24-0.37 mm/year) compared with the other 393 eyes in which subsequent exudative nAMD did not develop (0.28 mm/year; 95% CI, 0.26-0.29 mm/year; P = 0.37).

CONCLUSIONS

In eyes with recent GA, GA enlargement before the development of exudative nAMD seems slowed. This association was not observed in eyes with more long-standing GA, which have larger lesion sizes. Hence, perilesional nonexudative choroidal neovascular tissue (presumably present before the development of clinically apparent exudation) may slow enlargement of smaller GA lesions through improved perfusion. This hypothesis warrants further evaluation in prospective studies.

Modulation of Tmem135 Leads to Retinal Pigmented Epithelium Pathologies in Mice

Purpose

Aging is a critical risk factor for the development of retinal diseases, but how aging perturbs ocular homeostasis and contributes to disease is unknown. We identified transmembrane protein 135 (Tmem135) as a gene important for regulating retinal aging and mitochondrial dynamics in mice. Overexpression of Tmem135 causes mitochondrial fragmentation and pathologies in the hearts of mice. In this study, we examine the eyes of mice overexpressing wild-type Tmem135 (Tmem135 TG) and compare their phenotype to Tmem135 mutant mice.

Methods

Eyes were collected for histology, immunohistochemistry, electron microscopy, quantitative PCR, and Western blot analysis. Before tissue collection, electroretinography (ERG) was performed to assess visual function. Mouse retinal pigmented epithelium (RPE) cultures were established to visualize mitochondria.

Results

Pathologies were observed only in the RPE of Tmem135 TG mice, including degeneration, migratory cells, vacuolization, dysmorphogenesis, cell enlargement, and basal laminar deposit formation despite similar augmented levels of Tmem135 in the eyecup (RPE/choroid/sclera) and neural retina. We observed reduced mitochondria number and size in the Tmem135 TG RPE. ERG amplitudes were decreased in 365-day-old mice overexpressing Tmem135 that correlated with reduced expression of RPE cell markers. In Tmem135 mutant mice, RPE cells are thicker, smaller, and denser than their littermate controls without any signs of degeneration.

Conclusions

Overexpression and mutation of Tmem135 cause contrasting RPE abnormalities in mice that correlate with changes in mitochondrial shape and size (overfragmented in TG vs. overfused in mutant). We conclude proper regulation of mitochondrial homeostasis by TMEM135 is critical for RPE health.

Role of retinal pigment epithelium in age-related macular disease: a systematic review

Age-related macular disease (AMD) is a major cause of blindness and there is little treatment currently available by which the progress of the basic disorder can be modulated. Histological and clinical studies show that the major tissues involved are the outer retina, retinal pigment epithelium, Bruch's membrane and choroid. Because of a wide variation of phenotype from one case to another, it has been suggested that accurate phenotyping would be necessary for assessment of the effectiveness of treatment that is tissue-directed. However, based on findings from the study of human donor material and animal models of disease and of cell culture, it is concluded that retinal pigment epithelial dysfunction plays a central role in the disease process in most, if not all, cases of early AMD. The metabolism of phagosomal material, particularly lipids, and energy generation are interdependent, and dysfunction of both appears to be important in the genesis of disease. Evidence exists to suggest that both can be modulated therapeutically. These metabolic functions are amenable to further investigation in both the normal state and in disease. Once fully characterised, it is likely that treatment could be directed towards a limited number of functions in single tissue, thus simplifying treatment strategies.

Correlation between Visual Functions and Retinal Morphology in Eyes with Early and Intermediate Age-Related Macular Degeneration

In early and intermediate age related macular degeneration (ARMD), visual acuity alone has failed to explain the complete variation of vision. The aim of the present study was to determine correlation between different visual functions and retinal morphology in eyes with early and intermediate ARMD. In this single center cross sectional study, patients diagnosed as early or intermediate ARMD in at least one eye were recruited. Visual functions measured were best- corrected distance visual acuity (DVA), near vision acuity (NVA), reading speed (RS), and contrast sensitivity (CS). Parameters such as thickness (RT) and volume (RV) of the retina, outer retinal layer thickness (ORLT) and volume (ORLV), outer nuclear layer thickness (ONLT) and volume (ONLV), retinal pigment epithelium layer-Bruch’s membrane complex thickness (RPET) and volume (RPEV) were assessed employing semi-auto segmentation method of Spectralis optical coherence tomography (OCT). Twenty-six eyes were evaluated. DVA, CS, and RS showed significantly good correlation with RPET, ONLT, and ONLV, whereas NVA showed good correlation with ONLV and RPET. The present study concluded that RS, CS, NVA, and DVA represent the morphological alteration in early stages and should be tested in clinical settings. ONLT, ONLV, and RPET morphological parameters can be employed as important biomarkers in diagnosis of early to intermediate ARMD.