Emixustat Hydrochloride for Geographic Atrophy Secondary to Age-Related Macular Degeneration: A Randomized Clinical Trial

Customized Evaluation of Progressive Visual Sensitivity Loss in Geographic Atrophy to Improve the Power of Clinical Trials

Purpose

To evaluate the effectiveness of different approaches for customizing the selection of a subset of test locations on defect-mapping microperimetry (DMP) for improving the detection of progressive visual function decline in geographic atrophy (GA).

Design

Prospective longitudinal study.

Participants

Sixty eyes from 53 participants with GA secondary to age-related macular degeneration.

Methods

Participants underwent 3-monthly DMP testing twice at each visit for up to 24 months, where the extent of deep visual sensitivity losses on each test was determined through single presentations of 10-decibel stimuli at 208 locations within the central 8° radius region. Seven outcome measures were derived, which included evaluating the proportion of locations missed (PLM; showing nonresponse to stimuli) on DMP in a subset of test locations based on their proximity to the GA margin, or to locations neighboring repeatably nonresponding points on 2 baseline tests (i.e., missed both tests at baseline). These outcome measures were compared by their coefficient of variation (CoV; reflecting performance for capturing longitudinal changes) and sample size estimates in a 2-arm trial seeking to detect a ≥30% treatment effect. Changes in GA extent and best-corrected visual acuity (BCVA) were evaluated for comparison.

Main Outcome Measures

Coefficient of variation and sample size estimates.

Results

Evaluating PLM at points immediately adjacent (<1°) to repeatably nonresponding test locations at baseline (CoV = 47%) was the best performing outcome measure on DMP testing. This measure outperformed BCVA (CoV = 188%; P < 0.001) at detecting longitudinal changes and was comparable to evaluating GA extent (CoV = 58%; P = 0.097). Sample size requirements in a 24-month trial using this outcome measure on DMP testing were lower by 46% and 94% compared with evaluating GA extent and BCVA, respectively.

Conclusions

Customized evaluation of DMP functional testing results in regions adjacent to repeatably nonresponding locations at baseline improved the detection of longitudinal changes compared with the evaluation of all test locations. These findings show that it is possible to sensitively capture progressive visual function decline with this approach, supporting its use in future GA treatment trials.

Financial Disclosures

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

Advances and therapeutic opportunities in visual cycle modulation

The visual cycle is a metabolic pathway that enables continuous vision by regenerating the 11-cis-retinal chromophore for photoreceptors opsins. Although integral to normal visual function, the flux of retinoids through this cycle can contribute to a range of retinal pathologies, including Stargardt disease, age-related macular degeneration, and diabetic retinopathy. In such conditions, intermediates and byproducts of the visual cycle, such as bisretinoid components of lipofuscin, can accumulate, concomitant with cellular damage and eventual photoreceptor loss. This has inspired efforts to modulate the visual cycle, aiming to slow or prevent the formation of these toxic intermediates and thus preserve retinal structure and function. Over the past two decades, multiple strategies to modulate the visual cycle have emerged. These include both intrinsic approaches, targeting key enzymes, retinoid-binding proteins, or receptors within the pigment epithelium or photoreceptors (e.g., RPE65, CRBP1, and rhodopsin inhibitors/antagonists) and extrinsic strategies that indirectly alter retinoid availability within the retina (e.g., RBP4 antagonists). Many of these agents have shown promise in animal models of visual cycle-associated retinal diseases, reducing pathological changes, and improving retinal survival. Several have advanced into clinical studies, although none are currently FDA-approved. Challenges remain in optimizing drug specificity and duration of action while minimizing side effects such as nyctalopia. In this review, we comprehensively examine current and emerging visual cycle modulators, discuss their medicinal chemistry, mechanisms of action, efficacy in preclinical and clinical studies, and highlight future opportunities for drug discovery aimed at safely and effectively preserving vision through modulation of this biochemical pathway.

[Pharmacotherapy of ABCA4-associated Retinal Dystrophies]

ABCA4-associated retinal dystrophies, including Stargardt's disease, comprise a heterogeneous group of inherited retinal diseases caused by mutations in the ABCA4 gene and are inherited in an autosomal recessive manner. These diseases cause vision loss due to progressive degeneration of photoreceptors and retinal pigment epithelium, for which there is currently no approved treatment available. Based on the progress made in recent years and the well-understood pathobiology, promising therapeutic approaches have reached the clinical development phase, with pharmacological approaches being among the most advanced therapeutic options. Preclinical and clinical studies show progress in the development of drugs that have the potential to slow the progression of these diseases. Among these are compounds that have the potential to reduce lipofuscin accumulation in the retina, slow the formation of toxic vitamin A dimers or remove lipofuscin from the retina. Other substances interfere with the vitamin A metabolism in the visual cycle by reducing the amount of available vitamin A in the eye, which should lead to lower formation of toxic metabolic by-products. This article summarises the underlying pathophysiology of ABCA4-associated retinal degeneration and provides an overview of current pharmacological treatment approaches.

Determinants of Four-Year Visual Acuity Loss in Geographic Atrophy: An Analysis of Age-Related Eye Disease Study and Age-Related Eye Disease Study 2

PURPOSE

To investigate the relationship between geographic atrophy (GA) progression and change in best-corrected visual acuity (BCVA) over 4 years and identify factors associated with faster BCVA loss.

DESIGN

Secondary analysis of 2 randomized controlled clinical trials.

PARTICIPANTS

Age-Related Eye Disease Study (AREDS) and AREDS2 participants with GA secondary to nonexudative age-related macular degeneration.

METHODS

Baseline and annual color fundus photographs were assessed for GA area and proximity to the foveal center. Best-corrected visual acuity was measured using Early Treatment Diabetic Retinopathy Study logarithm of the minimum angle of resolution (logMAR) charts. Analyses included BCVA change over 4 years, with the relationship of BCVA decline with GA progression and other baseline factors examined using multivariable linear mixed-effects models.

MAIN OUTCOME MEASURES

The primary outcome was BCVA change over 4 years. Secondary outcomes included BCVA change from baseline to years 1, 2, and 3.

RESULTS

We included 1351 eyes from 994 participants, including 594 eyes from 464 participants with 4-year BCVA follow-up. Higher baseline BCVA, smaller baseline GA proximity to the foveal center, and greater GA growth rate were each independently associated with larger BCVA loss over 4 years (each P < 0.001). Among the 594 eyes with 4-year BCVA data, 69 eyes with a baseline BCVA < 40 letters (Snellen equivalent of 20/160 or worse) and 42 eyes with baseline GA located more than 1 mm from the foveal center did not experience significant BCVA loss over 4 years. In contrast, 483 eyes that met both criteria of baseline BCVA ≥ 40 letters and GA lesions involving or within 1 mm of the foveal center showed significant BCVA loss over 4 years (mean change = -11.33 letters [95% confidence interval = -12.80 to -9.84]), with faster GA progression associated with larger BCVA loss (P < 0.001).

CONCLUSIONS

In this cohort, eyes with GA involving or within 1 mm of the foveal center and a baseline BCVA of ≥ 40 letters appeared more likely to experience significant BCVA loss, suggesting these eyes may benefit more from therapies that slow GA progression. Our findings support a personalized approach to managing patients with GA, potentially guiding the design of future GA trials.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Progression Rate of Macular Retinal Pigment Epithelium Atrophy in Geographic Atrophy and Selected Inherited Retinal Dystrophies. A Systematic Review and Meta-Analysis

PURPOSE

To compare the macular retinal pigment epithelium (RPE) atrophy progression rate of selected degenerative and macular inherited retinal diseases (IRD).

DESIGN

Systematic review and meta-analysis.

METHODS

The protocol was registered on the PROSPERO database. Medline, Embase, Web of Science, Cochrane Central Register of Controlled Trials, and Google Scholar were searched up to September 15, 2023 for articles reporting the RPE atrophy growth rate in treatment-naïve eyes with geographic atrophy (GA), Stargardt disease (STGD1), Best disease, pseudoxanthoma elasticum (PXE), central areolar choroidal dystrophy (CACD), or pattern dystrophies with no previous or current macular neovascularization and a minimum follow-up time of 12 months. Meta-analyses determined mean RPE atrophy growth rates per disease, imaging modality (fundus autofluorescence [FAF], optical coherence tomography [OCT], or color fundus photography [CFP]) and metric (mm2/y or mm/y). The Newcastle-Ottawa scale and the Cochrane Risk-of-Bias tool assessed the risk of bias, and funnel plots were used to evaluate small-study effects.

RESULTS

From 4354 publications, 85 were included for meta-analysis: 69 studies (7815 eyes) on GA, 15 (1367 eyes) on STGD1, and one on both. Two studies on PXE were only eligible for review. No studies for other diseases met our eligibility criteria. The overall mean RPE atrophy growth rate for GA using FAF was 1.65 mm2/y (95% confidence interval [CI], 1.49-1.81) and 0.35 mm/y (95% CI, 0.28-0.41); using OCT, it was 1.46 mm2/y (95% CI, 1.28-1.64) and 0.34 mm/y (95% CI, 0.28-0.40); and on CFP it was 1.76 mm2/y (95% CI, 1.56-1.97) and 0.30 mm/y (95% CI, 0.28-0.31). For STGD1, using FAF it was 1.0 mm2/y (95% CI, 0.77-1.23) and 0.20 mm/y (95% CI, 0.17-0.23); on OCT, it was 0.80 mm2/y (95% CI, 0.72-0.88). No studies on STGD1 reported the growth rate with other imaging modalities or metrics. Growth rates in GA were faster than in STGD1 (p < .05). A larger baseline area of atrophy was generally associated with faster growth rates.

CONCLUSIONS

The RPE atrophy growth rate in GA is faster than in STGD1 but with great variation between studies and imaging modalities. Limited information was available for other macular IRD, suggesting further research is needed.

Informing Endpoints for Clinical Trials of Geographic Atrophy

Geographic atrophy (GA), the non-neovascular advanced form of age-related macular degeneration, remains an important disease area in which treatment needs are currently unmet. Recent clinical trials using drugs that target the complement pathway have shown modest yet consistent reductions in GA expansion but without commensurate changes in measures of visual function. In this review, we summarize information from the wide range of studies describing the characteristics of GA morphology and enumerate the factors influencing the growth rates of lesions and the directionality of expansion. In addition, we review the relationship between GA growth and the various measures of vision that reflect changes in function. We consider the reasons for the discordance between the anatomical and functional endpoints in current use and discuss methods to align these key outcomes.

Emerging Oral Pharmaceuticals for Dry Age-Related Macular Degeneration: Mechanism of Action, Current Clinical Status, and Future Directions

Dry age-related macular degeneration (AMD) has been historically managed with lifestyle modifications, monitoring for conversion to wet AMD, and vitamins. Recently there has been a flurry of research focused on discovering new targets to prevent worsening of dry AMD. In 2023, the US Food and Drug Administration approved the first two intravitreal complement inhibitors to slow the rate of geographic atrophy progression. However, serial intravitreal injections for a chronic progressive disease are burdensome for patients and have procedural risks. Therefore, there is significant research to discover novel oral medications to manage dry AMD. Several oral medications are currently in phase 2 and 3 clinical trials for dry AMD, whereas others have had recent readouts on their clinical trials and efficacy. The purpose of this review is to describe the therapeutic pathways currently being investigated and to provide an update on the clinical status of novel oral medications for the management of dry AMD. [Ophthalmic Surg Lasers Imaging Retina 2024;55:528-534.].

Advancements in Imaging and Therapeutic Options for Dry Age-Related Macular Degeneration and Geographic Atrophy

Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly, with dry AMD (d-AMD) leading to geographic atrophy (GA) and significant visual impairment. Multimodal imaging plays a crucial role in d-AMD diagnosis and management, allowing for detailed classification of patient phenotypes and aiding in treatment planning and prognosis determination. Treatment approaches for d-AMD have recently witnessed profound change with the development of specific drugs targeting the complement cascade, with the first anticomplement agents recently approved for GA treatment. Additionally, emerging strategies such as gene therapy and laser treatments may offer potential benefits, though further research is needed to fully establish their efficacy. However, the lack of effective therapies capable of restoring damaged retinal cells remains a major challenge. In the future, genetic treatments aimed at preventing the progression of d-AMD may emerge as a powerful approach. Currently, however, their development is still in the early stages.

METformin for the MINimization of Geographic Atrophy Progression (METforMIN): A Randomized Trial

Purpose

Metformin use has been associated with a decreased risk of age-related macular degeneration (AMD) progression in observational studies. We aimed to evaluate the efficacy of oral metformin for slowing geographic atrophy (GA) progression.

Design

Parallel-group, multicenter, randomized phase II clinical trial.

Participants

Participants aged ≥ 55 years without diabetes who had GA from atrophic AMD in ≥ 1 eye.

Methods

We enrolled participants across 12 clinical centers and randomized participants in a 1:1 ratio to receive oral metformin (2000 mg daily) or observation for 18 months. Fundus autofluorescence imaging was obtained at baseline and every 6 months.

Main Outcome Measures

The primary efficacy endpoint was the annualized enlargement rate of the square root-transformed GA area. Secondary endpoints included best-corrected visual acuity (BCVA) and low luminance visual acuity (LLVA) at each visit.

Results

Of 66 enrolled participants, 34 (57 eyes) were randomized to the observation group and 32 (53 eyes) were randomized to the treatment group. The median follow-up duration was 13.9 and 12.6 months in the observation and metformin groups, respectively. The mean ± standard error annualized enlargement rate of square root transformed GA area was 0.35 ± 0.04 mm/year in the observation group and 0.42 ± 0.04 mm/year in the treatment group (risk difference = 0.07 mm/year, 95% confidence interval = -0.05 to 0.18 mm/year; P = 0.26). The mean ± standard error decline in BCVA was 4.8 ± 1.7 letters/year in the observation group and 3.4 ± 1.1 letters/year in the treatment group (P = 0.56). The mean ± standard error decline in LLVA was 7.3 ± 2.5 letters/year in the observation group and 0.8 ± 2.2 letters/year in the treatment group (P = 0.06). Fourteen participants in the metformin group experienced nonserious adverse events related to metformin, with gastrointestinal side effects as the most common. No serious adverse events were attributed to metformin.

Conclusions

The results of this trial as conducted do not support oral metformin having effects on reducing the progression of GA. Additional placebo-controlled trials are needed to explore the role of metformin for AMD, especially for earlier stages of the disease.

Financial Disclosures

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

Quantitative Autofluorescence at AMD's Beginnings Highlights Retinal Topography and Grading System Differences: ALSTAR2 Baseline

INTRODUCTION

The aims of the study were to describe baseline quantitative (short-wavelength) autofluorescence (qAF) findings in a large pseudophakic cohort at age-related macular degeneration (AMD)'s beginnings and to assess qAF8 as an outcome measure and evaluate Age-Related Eye Disease Study (AREDS) and Beckman grading systems.

METHODS

In the ALSTAR2 baseline cohort (NCT04112667), 346 pseudophakic eyes of 188 persons (74.0 ± 5.5 years) were classified as normal (N = 160 by AREDS, 158 by Beckman), early AMD (eAMD) (N = 104, 66), and intermediate AMD (iAMD) (N = 82, 122). Groups were compared via mean qAF intensities in a 6°-8° annulus (qAF8) and maps of differences between observations and the overall mean, divided by standard deviation (Z-score).

RESULTS

qAF8 did not differ significantly among diagnostic groups by either stratification (p = 0.0869 AREDS; p = 0.0569 by Beckman). Notably, 45 eyes considered eAMD by AREDS became iAMD by Beckman. For AREDS-stratified eyes, Z-score maps showed higher centrally located qAF for normal, near the mean in eAMD, and lower values for iAMD. Maps deviated from this pattern for Beckman-stratified eyes.

CONCLUSIONS

In a large sample of pseudophakic eyes, qAF8 does not differ overall from normal aging to iAMD but also does not capture the earliest AMD activity in the macula lutea. AREDS classification gives results more consistent with a slow decline in histologic autofluorescence than Beckman classification.

Targeted High-Density Microperimetry Testing of Nascent Geographic Atrophy in Age-Related Macular Degeneration

Purpose

To examine the effectiveness of a targeted high-density microperimetry testing strategy for detecting visual sensitivity abnormalities in eyes with nascent geographic atrophy (nGA) when compared with standard central microperimetry testing.

Design

Observational study.

Participants

Three-hundred and twenty-one eyes from 176 individuals with nonneovascular age-related macular degeneration (AMD).

Methods

Thirty-five eyes from 33 participants underwent targeted high-density microperimetry testing of atrophic lesions (either nGA or geographic atrophy [GA]) within a 1.75° radius (or approximately 1000 μm diameter) region. Another cohort of 286 eyes from 143 participants with bilateral large drusen at baseline underwent standard microperimetry testing of the central 6° radius region at 6-monthly intervals for up to 36 months and thus included eyes that developed nGA and GA over the follow-up. All eyes underwent 2 tests at each visit to evaluate intrasession measurement repeatability.

Main Outcome Measures

Magnitude of visual sensitivity abnormalities based on mean sensitivity (MS), pointwise sensitivity standard deviation (PSD), and the number of test locations with a threshold of ≤ 10 decibels (dB; or deep defects) in eyes with nGA, compared between eyes that underwent targeted high-density microperimetry testing and standard central microperimetry testing.

Results

The magnitude of visual sensitivity abnormalities based on MS, PSD and the number of deep defects were all significantly greater in eyes with nGA using targeted, high-density microperimetry testing compared with eyes with nGA using standard central microperimetry testing (all P < 0.001) and were all significantly less than eyes with GA using targeted, high-density microperimetry testing (all P ≤ 0.004). The intrasession coefficient of repeatability, where 95% of the test-retest differences are expected to occur, for MS in eyes with atrophic changes was 0.9 dB with the targeted, high-density microperimetry testing, and 1.8 dB with standard central microperimetry testing.

Conclusions

Targeted, high-density microperimetry testing enabled the detection of a significantly greater magnitude of visual sensitivity abnormalities in eyes with nGA than standard microperimetry testing.

Financial Disclosures

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

A novel lipophenol quercetin derivative to prevent macular degeneration: Intravenous and oral formulations for preclinical pharmacological evaluation

Drugs with properties against oxidative and carbonyl stresses are potential candidates to prevent dry age-related macular degeneration (Dry-AMD) and inherited Stargardt disease (STGD1). Previous studies have demonstrated the capacity of a new lipophenol drug: 3-O-DHA-7-O-isopropyl-quercetin (Q-IP-DHA) to protect ARPE19 and primary rat RPE cells respectively from A2E toxicity and under oxidative and carbonyl stress conditions. In this study, first, a new methodology has been developed to access gram scale of Q-IP-DHA. After classification of the lipophenol as BCS Class IV according to physico-chemical and biopharmaceutical properties, an intravenous formulation with micelles (M) and an oral formulation using lipid nanocapsules (LNC) were developed. M were formed with Kolliphor® HS 15 and saline solution 0.9 % (mean size of 16 nm, drug loading of 95 %). The oral formulation was optimized and successfully allowed the formation of LNC (25 nm, 96 %). The evaluation of the therapeutic potency of Q-IP-DHA was performed after IV administration of micelles loaded with Q-IP-DHA (M-Q-IP-DHA) at 30 mg/kg and after oral administration of LNC loaded with Q-IP-DHA (LNC-Q-IP-DHA) at 100 mg/kg in mice. Results demonstrated photoreceptor protection after induction of retinal degeneration by acute light stress making Q-IP-DHA a promising preventive candidate against dry-AMD and STGD1.

Updates on Emerging Interventions for Autosomal Recessive ABCA4-Associated Stargardt Disease

Autosomal recessive Stargardt disease (STGD1) is an inherited retinal degenerative disease associated with a mutated ATP-binding cassette, subfamily A, member 4 (ABCA4) gene. STGD1 is the most common form of juvenile macular degeneration with onset in late childhood to early or middle adulthood and causes progressive, irreversible visual impairment and blindness. No effective treatment is currently available. In the present article, we review the most recent updates in clinical trials targeting the management of STGD1, including gene therapy, small molecule therapy, and stem cell therapy. In gene therapy, dual adeno-associated virus and non-viral vectors have been successful in delivering the human ABCA4 gene in preclinical studies. For pharmaceutical therapies ALK-001, deuterated vitamin A shows promise with preliminary data for phase 2 trial, demonstrating a decreased atrophy growth rate after two years. Stem cell therapy using human pluripotent stem cell-derived retinal pigment epithelium cells demonstrated long-term safety three years after implantation and visual acuity improvements in the first two years after initiation of therapy. Many other treatment options have ongoing investigations and clinical trials. While multiple potential interventions have shown promise in attenuating disease progression, further exploration is necessary to demonstrate treatment safety and efficacy.

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.

The Role of Inflammation in Age-Related Macular Degeneration-Therapeutic Landscapes in Geographic Atrophy

Age-related macular degeneration (AMD) is the leading cause of vision loss and visual impairment in people over 50 years of age. In the current therapeutic landscape, intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapies have been central to the management of neovascular AMD (also known as wet AMD), whereas treatments for geographic atrophy have lagged behind. Several therapeutic approaches are being developed for geographic atrophy with the goal of either slowing down disease progression or reversing sight loss. Such strategies target the inflammatory pathways, complement cascade, visual cycle or neuroprotective mechanisms to slow down the degeneration. In addition, retinal implants have been tried for vision restoration and stem cell therapies for potentially a dual purpose of slowing down the degeneration and restoring visual function. In particular, therapies focusing on the complement pathway have shown promising results with the FDA approved pegcetacoplan, a complement C3 inhibitor, and avacincaptad pegol, a complement C5 inhibitor. In this review, we discuss the mechanisms of inflammation in AMD and outline the therapeutic landscapes of atrophy AMD. Improved understanding of the various pathway components and their interplay in this complex neuroinflammatory degeneration will guide the development of current and future therapeutic options, such as optogenetic therapy.

Tuning the Metabolic Stability of Visual Cycle Modulators through Modification of an RPE65 Recognition Motif

In the eye, the isomerization of all-trans-retinal to 11-cis-retinal is accomplished by a metabolic pathway termed the visual cycle that is critical for vision. RPE65 is the essential trans-cis isomerase of this pathway. Emixustat, a retinoid-mimetic RPE65 inhibitor, was developed as a therapeutic visual cycle modulator and used for the treatment of retinopathies. However, pharmacokinetic liabilities limit its further development including: (1) metabolic deamination of the γ-amino-α-aryl alcohol, which mediates targeted RPE65 inhibition, and (2) unwanted long-lasting RPE65 inhibition. We sought to address these issues by more broadly defining the structure-activity relationships of the RPE65 recognition motif via the synthesis of a family of novel derivatives, which were tested in vitro and in vivo for RPE65 inhibition. We identified a potent secondary amine derivative with resistance to deamination and preserved RPE65 inhibitory activity. Our data provide insights into activity-preserving modifications of the emixustat molecule that can be employed to tune its pharmacological properties.

Methodological Appraisal of Phase 3 Clinical Trials in Geographic Atrophy

Geographic atrophy (GA) secondary to age-related macular degeneration is a common cause of blindness worldwide. Given the recent approval of the first therapy for GA, pegcetacoplan, we critically appraise methodological aspects of the phase 3 clinical trials published so far in this disease in relation to their design, analysis and interpretation. We reviewed some of the key attributes of all phase 3 clinical trials in GA available in the main public registry of clinical trials as of 20 May 2023. The topics discussed included types of endpoints, eligibility criteria, p-value and effect size, study power and sample size, the intention to treat principle, missing data, consistency of results, efficacy-safety balance and application of results. Five phase 3 clinical trials have reported results, either partially or completely: GATHER1, DERBY/OAKS, CHROMA/SPECTRI, SEATTLE and GATE. Although there are many similarities between these trials in terms of endpoints or broad eligibility criteria, they differ in several aspects (metric of the primary endpoint, sample size, type of adverse events, etc.) that can influence the results, which are discussed. Readers should understand key methodological aspects of clinical trials to improve their interpretation. On the other hand, authors should adhere to clinical trial reporting guidelines to communicate what was done and how it was done.

Geographic atrophy: Mechanism of disease, pathophysiology, and role of the complement system

Geographic atrophy (GA) is an advanced form of age-related macular degeneration (AMD), characterized by atrophic lesions that first start in the outer retina and progressively expand to cover the macula and the fovea, the center of the macula, leading to irreversible loss of vision over time. GA is distinct from wet or neovascular AMD (nAMD), the other form of advanced AMD. Neovascular AMD is characterized by new invading leaky blood vessels in the macula that can lead to acute vision loss. GA and nAMD may coexist in the same eye. The underlying pathophysiology of GA is complex and thought to involve chronic inflammation due to overactivation of the complement system that leads to the loss of photoreceptors, retinal pigment epithelium (RPE), and the underlying choriocapillaris. The disappearance of these structures appears as sharply demarcated atrophic lesions that are typical of GA. Researchers have reported about 1 million reported cases of GA in the United States, and about 160,000 cases occur per year. The most important risk factors for GA are increasing age and family history. Diagnosis of GA is usually made by using multimodal imaging techniques. Lesions associated with GA are highly heterogeneous, and the growth rate may differ from patient to patient. Despite the progressive nature of GA, the fovea may be spared until much later in the disease, thereby retaining central vision in patients. With time, atrophic lesions may progressively grow to involve the fovea, thereby severely impairing central vision. Vision loss can happen rapidly once the lesions reach the fovea. However, even without the involvement of the fovea, ongoing vision impairment impacting daily life may be present. Median time from GA not involving the center of the fovea (without subfoveal involvement) to GA with lesion boundary affecting the foveal center (subfoveal involvement) ranges from 1.4 to 2.5 years. GA can greatly impact patients' functioning and quality of life and limit their independence by interfering with activities of daily living, including difficulties with reading, driving, watching television, recognizing faces, and being unable to do household chores. No treatments have been available until intravitreal pegcetacoplan was recently approved by the US Food and Drug Administration for GA secondary to AMD. DISCLOSURES: Dr Bakri serves as a consultant to Apellis Pharmaceuticals, as well as AbbVie, Adverum, Eyepoint, iLumen, Iveric Bio, Genentech, Novartis, Outlook Therapeutics, Pixium, Regeneron, Roche, and Regenxbio. Drs Sharp, Luo, and Sarda are employees of Apellis Pharmaceuticals. Dr Bektas and Ms Khan are employees of RTI Health Solutions. Apellis developed and led the concept design of this publication, review and interpretation, approval, and decision to publish. This research was developed under a research contract between RTI Health Solutions and Apellis Pharmaceuticals and was funded by Apellis Pharmaceuticals. This supplement is to describe the disease of geographic atrophy and was funded by Apellis. Apellis Pharmaceuticals has developed Syfovre (pegcetacoplan), the first and only treatment for geographic atrophy.

Novel oral medications for retinal disease: an update on clinical development

PURPOSE OF REVIEW

Intravitreal and periocular injections for retinal disease provide a targeted delivery of medication to the eye. However, given risks of injections, including endophthalmitis, pain and treatment burden for both patients and retina specialists, there has been significant interest and effort in developing oral medications for the management of retinal disease. This article provides clinical and preclinical details of new oral medications in the pipeline for management of retinal disease.

RECENT FINDINGS

Several new oral medications show clinical and preclinical promise for the management of retinal disease, including macular degeneration, diabetic retinopathy and Stargardt disease.

SUMMARY

Oral medications provide promise for treating retinal disease, possibly increasing compliance, and reducing side effects of intravitreal or periocular injections. However, difficulties in this approach include systemic side effects and efficacy targeting the eye. There are multiple medications that are currently under investigation with the potential to act as stand-alone treatment or as an adjunct treatment for management of retinal diseases such as diabetic retinopathy, macular degeneration and Stargardt disease.

Advanced Therapy Medicinal Products for Age-Related Macular Degeneration; Scaffold Fabrication and Delivery Methods

Retinal degenerative diseases such as age-related macular degeneration (AMD) represent a leading cause of blindness, resulting in permanent damage to retinal cells that are essential for maintaining normal vision. Around 12% of people over the age of 65 have some form of retinal degenerative disease. Whilst antibody-based drugs have revolutionised treatment of neovascular AMD, they are only effective at an early stage and cannot prevent eventual progression or allow recovery of previously lost vision. Hence, there is a clear unmet need to find innovative treatment strategies to develop a long-term cure. The replacement of damaged retinal cells is thought to be the best therapeutic strategy for the treatment of patients with retinal degeneration. Advanced therapy medicinal products (ATMPs) are a group of innovative and complex biological products including cell therapy medicinal products, gene therapy medicinal products, and tissue engineered products. Development of ATMPs for the treatment of retinal degeneration diseases has become a fast-growing field of research because it offers the potential to replace damaged retinal cells for long-term treatment of AMD. While gene therapy has shown encouraging results, its effectiveness for treatment of retinal disease may be hampered by the body's response and problems associated with inflammation in the eye. In this mini-review, we focus on describing ATMP approaches including cell- and gene-based therapies for treatment of AMD along with their applications. We also aim to provide a brief overview of biological substitutes, also known as scaffolds, that can be used for delivery of cells to the target tissue and describe biomechanical properties required for optimal delivery. We describe different fabrication methods for preparing cell-scaffolds and explain how the use of artificial intelligence (AI) can aid with the process. We predict that combining AI with 3D bioprinting for 3D cell-scaffold fabrication could potentially revolutionise retinal tissue engineering and open up new opportunities for developing innovative platforms to deliver therapeutic agents to the target tissues.

Quantitative Autofluorescence in Non-Neovascular Age Related Macular Degeneration

Quantitative autofluorescence (qAF8) level is a presumed surrogate marker of lipofuscin content in the retina. We investigated the changes in the qAF8 levels in non-neovascular AMD. In this prospective cohort study, Caucasians aged ≥50 years with varying severity of non-neovascular AMD in at least one eye and Snellen visual acuity ≥6/18 were recruited. The qAF8 levels were analysed in the middle eight segments of the Delori pattern (HEYEX software, Heidelberg, Germany). The AMD categories were graded using both the Beckman classification and multimodal imaging (MMI) to include the presence of subretinal drusenoid deposits (SDD). A total of 353 eyes from 231 participants were analyzed. Compared with the age-matched controls, the qAF8 values decreased in the eyes with AMD (adjusted % difference = -19.7% [95% CI -28.8%, -10.4%]; p < 0.001) and across the AMD categories, (adjusted % differences; Early, -13.1% (-24.4%, -1%), p = 0.04; intermediate AMD (iAMD), -22.9% (-32.3%, -13.1%), p < 0.001; geographic atrophy -25.2% (-38.1%, -10.4%), p = 0.002). On MMI, the qAF8 was reduced in the AMD subgroups relative to the controls, (adjusted % differences; Early, -5.8% (-18.9%, 8.3%); p = 0.40; iAMD, -26.7% (-36.2%, -15.6%); p < 0.001; SDD, -23.7% (-33.6%, -12.2%); p < 0.001; atrophy, -26.7% (-39.3%, -11.3%), p = 0.001). The qAF8 levels declined early in AMD and were not significantly different between the severity levels of non-neovascular AMD, suggesting the early and sustained loss of function of the retinal pigment epithelium in AMD.

Associations of systemic health and medication use with the enlargement rate of geographic atrophy in age-related macular degeneration

BACKGROUND

The associations of geographic atrophy (GA) progression with systemic health status and medication use are unclear.

METHODS

We manually delineated GA in 318 eyes in the Age-Related Eye Disease Study. We calculated GA perimeter-adjusted growth rate as the ratio between GA area growth rate and mean GA perimeter between the first and last visit for each eye (mean follow-up=5.3 years). Patients' history of systemic health and medications was collected through questionnaires administered at study enrolment. We evaluated the associations between GA perimeter-adjusted growth rate and 27 systemic health factors using univariable and multivariable linear mixed-effects regression models.

RESULTS

In the univariable model, GA perimeter-adjusted growth rate was associated with GA in the fellow eye at any visit (p=0.002), hypertension history (p=0.03), cholesterol-lowering medication use (p<0.001), beta-blocker use (p=0.02), diuretic use (p<0.001) and thyroid hormone use (p=0.03). Among the six factors, GA in the fellow eye at any visit (p=0.008), cholesterol-lowering medication use (p=0.002), and diuretic use (p<0.001) were independently associated with higher GA perimeter-adjusted growth rate in the multivariable model. GA perimeter-adjusted growth rate was 51.1% higher in patients with versus without cholesterol-lowering medication use history and was 37.8% higher in patients with versus without diuretic use history.

CONCLUSIONS

GA growth rate may be associated with the fellow eye status, cholesterol-lowering medication use, and diuretic use. These possible associations do not infer causal relationships, and future prospective studies are required to investigate the relationships further.

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.

The novel visual cycle inhibitor (±)-RPE65-61 protects retinal photoreceptors from light-induced degeneration

The visual cycle refers to a series of biochemical reactions of retinoids in ocular tissues and supports the vision in vertebrates. The visual cycle regenerates visual pigments chromophore, 11-cis-retinal, and eliminates its toxic byproducts from the retina, supporting visual function and retinal neuron survival. Unfortunately, during the visual cycle, when 11-cis-retinal is being regenerated in the retina, toxic byproducts, such as all-trans-retinal and bis-retinoid is N-retinylidene-N-retinylethanolamine (A2E), are produced, which are proposed to contribute to the pathogenesis of the dry form of age-related macular degeneration (AMD). The primary biochemical defect in Stargardt disease (STGD1) is the accelerated synthesis of cytotoxic lipofuscin bisretinoids, such as A2E, in the retinal pigment epithelium (RPE) due to mutations in the ABCA4 gene. To prevent all-trans-retinal-and bisretinoid-mediated retinal degeneration, slowing down the retinoid flow by modulating the visual cycle with a small molecule has been proposed as a therapeutic strategy. The present study describes RPE65-61, a novel, non-retinoid compound, as an inhibitor of RPE65 (a key enzyme in the visual cycle), intended to modulate the excessive activity of the visual cycle to protect the retina from harm degenerative diseases. Our data demonstrated that (±)-RPE65-61 selectively inhibited retinoid isomerase activity of RPE65, with an IC50 of 80 nM. Furthermore, (±)-RPE65-61 inhibited RPE65 via an uncompetitive mechanism. Systemic administration of (±)-RPE65-61 in mice resulted in slower chromophore regeneration after light bleach, confirming in vivo target engagement and visual cycle modulation. Concomitant protection of the mouse retina from high-intensity light damage was also observed. Furthermore, RPE65-61 down-regulated the cyclic GMP-AMP synthase stimulator of interferon genes (cGAS-STING) pathway, decreased the inflammatory factor, and attenuated retinal apoptosis caused by light-induced retinal damage (LIRD), which led to the preservation of the retinal function. Taken together, (±)-RPE65-61 is a potent visual cycle modulator that may provide a neuroprotective therapeutic benefit for patients with STGD and AMD.

Impact of Cataract Surgery on Low Luminance Visual Acuity Deficit Measurements

Purpose

The impact of cataract surgery on low luminance visual acuity deficit (LLVAD) measurements was investigated by measuring the LLVAD before and after cataract surgery.

Design

Prospective, longitudinal study.

Participants

Patients undergoing cataract surgery.

Methods

Photopic luminance (PL)–best-corrected visual acuity (BCVA) and low luminance (LL)–BCVA were obtained using the ETDRS chart. Low luminance visual acuity deficit scores were calculated by subtracting the LL-BCVA letter score from the PL-BCVA letter score. To demonstrate the reproducibility of these visual acuity measurements, we used data from drusen-only eyes previously published in the Complement Inhibition with Eculizumab for the Treatment of Nonexudative Age-Related Macular Degeneration (COMPLETE) study. The PL-BCVA, LL-BCVA, and LLVAD measurements obtained at an interval of 3 months in this cohort were used for comparison. In the current study, the impact of cataract surgery on LLVAD measurements was analyzed by comparing the PL-BCVA, LL-BCVA, and LLVAD measurements before and after cataract surgery.

Main Outcome Measures

The reproducibility of the visual acuity measurements and the changes in LLVAD measurement after cataract surgery.

Results

In the COMPLETE study, no clinically significant differences were found in the PL-BCVA, LL-BCVA, or LLVAD measurements between baseline and the 3-month follow-up visits with a change of –1.1 letters, –1.3 letters, and 0.1 letters, respectively (P = 0.02, P = 0.11, and P = 0.88, respectively). In the current study, significant increases were found in the PL-BCVA and LL-BCVA measurements, with a change of 7.3 letters and 10.2 letters after cataract surgery (P < 0.001 for both), and a statistically significant decrease in LLVAD measurements was found, with a change of –3.0 letters after cataract surgery (P = 0.002).

Conclusions

Because of the variable effect of cataracts on LL-BCVA measurements and the significant change in LLVAD measurements after cataract surgery, investigators should be aware that cataract surgery during a trial will have an unpredictable impact on LLVAD measurements, and pseudophakic and phakic patients should be analyzed separately.

Neuroinflammation and neurodegeneration in diabetic retinopathy

Diabetic retinopathy (DR) is the most common complication of diabetes and has been historically regarded as a microangiopathic disease. Now, the paradigm is shifting toward a more comprehensive view of diabetic retinal disease (DRD) as a tissue-specific neurovascular complication, in which persistently high glycemia causes not only microvascular damage and ischemia but also intraretinal inflammation and neuronal degeneration. Despite the increasing knowledge on the pathogenic pathways involved in DR, currently approved treatments are focused only on its late-stage vasculopathic complications, and a single molecular target, vascular endothelial growth factor (VEGF), has been extensively studied, leading to drug development and approval. In this review, we discuss the state of the art of research on neuroinflammation and neurodegeneration in diabetes, with a focus on pathophysiological studies on human subjects, in vivo imaging biomarkers, and clinical trials on novel therapeutic options.

Investigational drugs in clinical trials for macular degeneration

INTRODUCTION

Intravitreal anti-vascular endothelial growth factor (VEGF) injections for exudative age-related macular degeneration (eAMD) are effective and safe but require frequent injections and have nonresponding patients. Geographic atrophy/dry AMD (gaAMD) remains an unmet medical need . New therapies are needed to address this leading cause of blindness in the increasing aged population.

AREAS COVERED

This paper reviews the pathogenesis of macular degeneration, current and failed therapeutics, therapies undergoing clinical trials and a rationale for why certain AMD therapies may succeed or fail .

EXPERT OPINION

VEGF- inhibitors reduce both vascular leakage and neovascularization. Experimental therapies that only address neovascularization or leakage will unlikely supplant anti-VEGF therapies. The most promising future therapies for eAMD, are those that target, more potently inhibit and have a more sustained effect on the VEGF pathway such as KSI-301, RGX-314, CLS-AX, EYEP-1901, OTX-TKI.

GaAMD is a phenotype of phagocytic retinal cell loss. Inhibiting phagocytic activity of retinal microglial/macrophages at the border of GA and reducing complement derived activators of microglial/macrophage is the most promising strategy. Complement inhibitors (Pegcetacoplan and Avacincaptad pegol) will likely obtain FDA approval but will serve to pave the way for combined complement and direct phagocytic inhibitors such as AVD-104.

Recent Advances in Age-Related Macular Degeneration Therapies

Age-related macular degeneration (AMD) was described for the first time in the 1840s and is currently the leading cause of blindness for patients over 65 years in Western Countries. This disease impacts the eye’s posterior segment and damages the macula, a retina section with high levels of photoreceptor cells and responsible for the central vision. Advanced AMD stages are divided into the atrophic (dry) form and the exudative (wet) form. Atrophic AMD consists in the progressive atrophy of the retinal pigment epithelium (RPE) and the outer retinal layers, while the exudative form results in the anarchic invasion by choroidal neo-vessels of RPE and the retina. This invasion is responsible for fluid accumulation in the intra/sub-retinal spaces and for a progressive dysfunction of the photoreceptor cells. To date, the few existing anti-AMD therapies may only delay or suspend its progression, without providing cure to patients. However, in the last decade, an outstanding number of research programs targeting its different aspects have been initiated by academics and industrials. This review aims to bring together the most recent advances and insights into the mechanisms underlying AMD pathogenicity and disease evolution, and to highlight the current hypotheses towards the development of new treatments, i.e., symptomatic vs. curative. The therapeutic options and drugs proposed to tackle these mechanisms are analyzed and critically compared. A particular emphasis has been given to the therapeutic agents currently tested in clinical trials, whose results have been carefully collected and discussed whenever possible.

Transcriptomic and proteomic retinal pigment epithelium signatures of age-related macular degeneration

There are currently no treatments for geographic atrophy, the advanced form of age-related macular degeneration. Hence, innovative studies are needed to model this condition and prevent or delay its progression. Induced pluripotent stem cells generated from patients with geographic atrophy and healthy individuals were differentiated to retinal pigment epithelium. Integrating transcriptional profiles of 127,659 retinal pigment epithelium cells generated from 43 individuals with geographic atrophy and 36 controls with genotype data, we identify 445 expression quantitative trait loci in cis that are asssociated with disease status and specific to retinal pigment epithelium subpopulations. Transcriptomics and proteomics approaches identify molecular pathways significantly upregulated in geographic atrophy, including in mitochondrial functions, metabolic pathways and extracellular cellular matrix reorganization. Five significant protein quantitative trait loci that regulate protein expression in the retinal pigment epithelium and in geographic atrophy are identified - two of which share variants with cis- expression quantitative trait loci, including proteins involved in mitochondrial biology and neurodegeneration. Investigation of mitochondrial metabolism confirms mitochondrial dysfunction as a core constitutive difference of the retinal pigment epithelium from patients with geographic atrophy. This study uncovers important differences in retinal pigment epithelium homeostasis associated with geographic atrophy.

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.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

Correlation between Fundus Autofluorescence and En Face Optical Coherence Tomography Measurements of Geographic Atrophy

PURPOSE

To evaluate the correlation between fundus autofluorescence (FAF) and en face spectral-domain optical coherence tomography (SDOCT) measurements of geographic atrophy (GA) associated with age-related macular degeneration (AMD).

DESIGN

Retrospective, cross-sectional study.

PARTICIPANTS

270 eyes from 172 subjects with GA associated with AMD.

METHODS

Subjects with atrophic AMD with both fundus autofluorescence (FAF; Heidelberg HRA + Spectralis) and dense volume (128 B-scans over 6x6mm) spectral domain optical coherence tomography (SDOCT; Cirrus OCT) imaging were included in this retrospective analysis. The borders of all areas of definite decreased autofluorescence (DDAF) corresponding to GA were manually outlined on FAF images by certified graders at the Doheny Image Reading Center (DIRC) using validated planimetric grading tools. GA was also delineated automatically from en face OCT (at the level of the choroid) using instrument software (Cirrus v.6.2), and segmentation errors were manually corrected prior to computation of GA area. FAF and SDOCT derived measurements were correlated.

MAIN OUTCOME MEASURES

Correlation between SD-OCT and FAF measurements of GA area.

RESULTS

The mean GA area measured from FAF images was 8.1 ± 5.04 mm², compared with an automated, uncorrected SDOCT GA area of 6.82 ± 3.84 mm². Despite the presence of apparent OCT segmentation errors, there was a significant correlation between FAF and uncorrected SDOCT measurements (r = 0.80; P < 0.001). Following manual correction of SDOCT GA segmentation errors, the measured GA area increased to 7.29 ± 4.18 mm², and the correlation with the FAF-determined GA area significantly improved (r = 0.98; P < 0.001).

CONCLUSIONS

SDOCT-derived measurements of GA correlate well with areas of DDAF obtained from FAF images. Manual correction of SDOCT segmentation errors can further improve this correlation. These observations may support the use of SDOCT-based measurements of GA in clinical research and clinical trials.

A hierarchical Bayesian entry time realignment method to study the long-term natural history of diseases

A major question in clinical science is how to study the natural course of a chronic disease from inception to end, which is challenging because it is impractical to follow patients over decades. Here, we developed BETR (Bayesian entry time realignment), a hierarchical Bayesian method for investigating the long-term natural history of diseases using data from patients followed over short durations. A simulation study shows that BETR outperforms an existing method that ignores patient-level variation in progression rates. BETR, when combined with a common Bayesian model comparison tool, can identify the correct disease progression function nearly 100% of the time, with high accuracy in estimating the individual disease durations and progression rates. Application of BETR in patients with geographic atrophy, a disease with a known natural history model, shows that it can identify the correct disease progression model. Applying BETR in patients with Huntington's disease demonstrates that the progression of motor symptoms follows a second order function over approximately 20 years.

Progress of clinical therapies for dry age-related macular degeneration

Dry age-related macular degeneration (AMD) is a progressive blinding disease that currently affects millions of people worldwide with no successful treatment available. Significant research efforts are currently underway to develop therapies aimed at slowing the progression of this disease or, more notably, reversing it. Here the therapies which have reached clinical trial for treatment of dry AMD were reviewed. A thorough search of PubMed, Embase, and Clinicaltrials.gov has led to a comprehensive collection of the most recent strategies being evaluated. This review also endeavors to assess the status and future directions of therapeutics for this debilitating condition.

Reticular pseudodrusen: A critical phenotype in age-related macular degeneration

Reticular pseudodrusen (RPD), or subretinal drusenoid deposits (SDD), refer to distinct lesions that occur in the subretinal space. Over the past three decades, their presence in association with age-related macular degeneration (AMD) has become increasingly recognized, especially as RPD have become more easily distinguished with newer clinical imaging modalities. There is also an increasing appreciation that RPD appear to be a critical AMD phenotype, where understanding their pathogenesis will provide further insights into the processes driving vision loss in AMD. However, key barriers to understanding the current evidence related to the independent impact of RPD include the heterogeneity in defining their presence, and failure to account for the confounding impact of the concurrent presence and severity of AMD pathology. This review thus critically discusses the current evidence on the prevalence and clinical significance of RPD and proposes a clinical imaging definition of RPD that will help move the field forward in gathering further key knowledge about this critical phenotype. It also proposes a putative mechanism for RPD formation and how they may drive progression to vision loss in AMD, through examining current evidence and presenting novel findings from preclinical and clinical studies.

Local Progression Kinetics of Geographic Atrophy Depends Upon the Border Location

Purpose

To assess the influence of lesion morphology and location on geographic atrophy (GA) growth rate.

Methods

We manually delineated GA on color fundus photographs of 237 eyes in the Age-Related Eye Disease Study. We calculated local border expansion rate (BER) as the linear distance that a point on the GA border traveled over 1 year based on a Euclidean distance map. Eye-specific BER was defined as the mean local BER of all points on the GA border in an eye. The percentage area affected by GA was defined as the GA area divided by the total retinal area in the region.

Results

GA enlarged 1.51 ± 1.96 mm2 in area and 0.13 ± 0.11 mm in distance over 1 year. The GA area growth rate (mm2/y) was associated with the baseline GA area (P < 0.001), perimeter (P < 0.001), lesion number (P < 0.001), and circularity index (P < 0.001); in contrast, eye-specific BER (mm/y) was not significantly associated with any of these factors. As the retinal eccentricity increased from 0 to 3.5 mm, the local BER increased from 0.10 to 0.24 mm/y (P < 0.001); in contrast, the percentage of area affected by GA decreased from 49.3% to 2.3%.

Conclusions

Using distance-based measurements allows GA progression evaluation without significant confounding effects from baseline GA morphology. Local GA progression rates increased as a function of retinal eccentricity within the macula which is opposite of the trend for GA distribution, suggesting that GA initiation and enlargement may be mediated by different biological processes.

Retinal pigment epithelium 65 kDa protein (RPE65): An update

Vertebrate vision critically depends on an 11-cis-retinoid renewal system known as the visual cycle. At the heart of this metabolic pathway is an enzyme known as retinal pigment epithelium 65 kDa protein (RPE65), which catalyzes an unusual, possibly biochemically unique, reaction consisting of a coupled all-trans-retinyl ester hydrolysis and alkene geometric isomerization to produce 11-cis-retinol. Early work on this isomerohydrolase demonstrated its membership to the carotenoid cleavage dioxygenase superfamily and its essentiality for 11-cis-retinal production in the vertebrate retina. Three independent studies published in 2005 established RPE65 as the actual isomerohydrolase instead of a retinoid-binding protein as previously believed. Since the last devoted review of RPE65 enzymology appeared in this journal, major advances have been made in a number of areas including our understanding of the mechanistic details of RPE65 isomerohydrolase activity, its phylogenetic origins, the relationship of its membrane binding affinity to its catalytic activity, its role in visual chromophore production for rods and cones, its modulation by macromolecules and small molecules, and the involvement of RPE65 mutations in the development of retinal diseases. In this article, I will review these areas of progress with the goal of integrating results from the varied experimental approaches to provide a comprehensive picture of RPE65 biochemistry. Key outstanding questions that may prove to be fruitful future research pursuits will also be highlighted.

The Progression of Stargardt Disease Using Volumetric Hill of Vision Analyses Over 24 Months: ProgStar Report No.15

PURPOSE

To report the yearly rate of change in macular function in patients with Stargardt disease type 1 (STGD1) over 24 months and to establish a new volumetric visual function index for use in clinical trials investigating the efficacy on retinal sensitivity.

METHODS

Design: International, multicenter, prospective cohort study with 5 study visits every 6 months over 24 months.

PARTICIPANTS

A total of 233 individuals with genetically confirmed STGD1 (≥1 disease-causing ABCA4 variant).

MAIN OUTCOME MEASURES

The total volume (V_TOT) beneath the sensitivity surface of a 3-D model of the hill of vision and mean sensitivity (MS) derived from mesopic microperimetry performed with a white stimulus. Changes of V_TOT over time and its correlation with the ABCA4 genotype and baseline features.

RESULTS

At baseline, 440 eyes (233 patients) with a mean (SD) age of 33.7 (15.0) years, mean (SD) visual acuity of 46.08 (16.03) ETDRS letters were analyzed with an average V_TOT of 0.91 decibel-steradian (dB-sr) and an MS of 10.73 dB. The overall mean rate of decrease in sensitivity [95% confidence interval] was 0.077 [0.064, 0.090] dB-sr/y for V_TOT and 0.87 [0.72, 1.02] dB/year for MS. The progression rate of V_TOT depended on baseline visual function (0.029 dB-sr/year for low and 0.120 dB-sr/year for high baseline V_TOT; P < .001) and exhibited a difference in the first vs second year of follow-up (0.065 dB-sr/year vs 0.089 dB-sr/year, respectively; P < .001). The absence of pigmentary abnormalities of the retinal pigment epithelium at baseline was found to be associated with a faster progression rate (P < .001), whereas a significant association with the genotype was not detected (P = .7).

CONCLUSION

In STGD1, both microperimetric outcomes demonstrate statistically significant and clinically meaningful changes after relatively short follow-up periods. Volumetric modeling may be useful in future interventional clinical trials that aim to improve retinal sensitivity or to slow down its decline and for structure-function correlations.

Incidence of Newly Registered Blindness From Age-Related Macular Degeneration in Australia Over a 21-Year Period: 1996-2016

PURPOSE

Report the age-standardized annual incidence of blindness registration due to age-related macular degeneration (AMD) in Australia in patients aged 50 years and older. Frequencies of photodynamic therapy (PDT) and intravitreal therapy (IVT) were examined.

DESIGN

Retrospective observational study.

SETTING

Registry of the Association for the Blind of Western Australia with best-corrected visual acuity worse than 20/200 in the better-seeing eye.

PARTICIPANTS

Registering as blind aged 50 years or over.

MEASURES

Annual age-standardized incidence of blindness over 3 time periods: 1996-2001 (pre-PDT), 2002-2007 (PDT era) and 2008-2016 (IVT era). The rates of PDT and IVT usage were assessed.

RESULTS

Age-standardized annual incidence of blindness rose during the PDT era, reaching 72.5 cases per 100,000 person-years in 2004. The incidence declined from 2007 onwards, reaching 8.2 cases per 100,000 person-years in 2016 (IVT era). The age at AMD blindness registration increased from 82.7 to 84.9 and 83.7 to 86.0 years from the PDT era to the IVT era in both male and females (P < 0.001) respectively. Over the same time period, PDT usage increased in 2002 and declined in 2006, whereas IVT usage increased from 2009 by 3745 per year.

CONCLUSION

The increase in new blindness registrations due to AMD coincided with public funding of verteporfin for PDT, whereas the subsequent decline occurred when bevacizumab was used off-label and ranibizumab and aflibercept were publicly funded. An understanding of the effect of retinal therapy on public health measures may inform improvements in the allocation of limited resources.

Clinically relevant deep learning for detection and quantification of geographic atrophy from optical coherence tomography: a model development and external validation study

BACKGROUND

Geographic atrophy is a major vision-threatening manifestation of age-related macular degeneration, one of the leading causes of blindness globally. Geographic atrophy has no proven treatment or method for easy detection. Rapid, reliable, and objective detection and quantification of geographic atrophy from optical coherence tomography (OCT) retinal scans is necessary for disease monitoring, prognostic research, and to serve as clinical endpoints for therapy development. To this end, we aimed to develop and validate a fully automated method to detect and quantify geographic atrophy from OCT.

METHODS

We did a deep-learning model development and external validation study on OCT retinal scans at Moorfields Eye Hospital Reading Centre and Clinical AI Hub (London, UK). A modified U-Net architecture was used to develop four distinct deep-learning models for segmentation of geographic atrophy and its constituent retinal features from OCT scans acquired with Heidelberg Spectralis. A manually segmented clinical dataset for model development comprised 5049 B-scans from 984 OCT volumes selected randomly from 399 eyes of 200 patients with geographic atrophy secondary to age-related macular degeneration, enrolled in a prospective, multicentre, phase 2 clinical trial for the treatment of geographic atrophy (FILLY study). Performance was externally validated on an independently recruited dataset from patients receiving routine care at Moorfields Eye Hospital (London, UK). The primary outcome was segmentation and classification agreement between deep-learning model geographic atrophy prediction and consensus of two independent expert graders on the external validation dataset.

FINDINGS

The external validation cohort included 884 B-scans from 192 OCT volumes taken from 192 eyes of 110 patients as part of real-life clinical care at Moorfields Eye Hospital between Jan 1, 2016, and Dec, 31, 2019 (mean age 78·3 years [SD 11·1], 58 [53%] women). The resultant geographic atrophy deep-learning model produced predictions similar to consensus human specialist grading on the external validation dataset (median Dice similarity coefficient [DSC] 0·96 [IQR 0·10]; intraclass correlation coefficient [ICC] 0·93) and outperformed agreement between human graders (DSC 0·80 [0·28]; ICC 0·79). Similarly, the three independent feature-specific deep-learning models could accurately segment each of the three constituent features of geographic atrophy: retinal pigment epithelium loss (median DSC 0·95 [IQR 0·15]), overlying photoreceptor degeneration (0·96 [0·12]), and hypertransmission (0·97 [0·07]) in the external validation dataset versus consensus grading.

INTERPRETATION

We present a fully developed and validated deep-learning composite model for segmentation of geographic atrophy and its subtypes that achieves performance at a similar level to manual specialist assessment. Fully automated analysis of retinal OCT from routine clinical practice could provide a promising horizon for diagnosis and prognosis in both research and real-life patient care, following further clinical validation FUNDING: Apellis Pharmaceuticals.

COMPARISON OF SPECTRALIS AND CIRRUS OPTICAL COHERENCE TOMOGRAPHY FOR THE DETECTION OF INCOMPLETE AND COMPLETE RETINAL PIGMENT EPITHELIUM AND OUTER RETINAL ATROPHY

PURPOSE

To evaluate and compare the detection of incomplete and complete retinal pigment epithelial and outer retinal atrophy (iRORA and cRORA) using Spectralis and Cirrus optical coherence tomography (OCT) devices.

METHODS

Subjects with late age-related macular degeneration were imaged on the same day with Spectralis and Cirrus OCT. Two, masked, independent, and experienced retina specialist graders evaluated each case for the presence of cRORA and iRORA lesions.

RESULTS

A significantly higher number of lesions were observed using Spectralis compared with Cirrus (239 vs. 226 and 223 vs. 209). Higher number of iRORA lesions were identified with Spectralis (105 vs. 90 and 96 vs. 82), and no significant difference was observed between devices for cRORA lesions (134 vs. 136 and 128 vs. 126). When considering the presence or absence of iRORA or cRORA, the agreement between devices for both graders was excellent for cRORA and good for iRORA.

CONCLUSION

Spectralis and Cirrus OCT identified a similar number of cRORA lesions, although more iRORA lesions could be detected with Spectralis OCT. These findings may have implications for developing acquisition protocols for trials based on the intended atrophy targets and highlight the importance of using a consistent OCT instrument across a study.

Biomarkers for Nonexudative Age-Related Macular Degeneration and Relevance for Clinical Trials: A Systematic Review

TOPIC

The purpose of the review was to identify structural, functional, blood-based, and other types of biomarkers for early, intermediate, and late nonexudative stages of age-related macular degeneration (AMD) and summarize the relevant data for proof-of-concept clinical trials.

CLINICAL RELEVANCE

AMD is a leading cause of blindness in the aging population, yet no treatments exist for its most common nonexudative form. There are limited data on the diagnosis and progression of nonexudative AMD compared to neovascular AMD. Our objective was to provide a comprehensive, systematic review of recently published biomarkers (molecular, structural, and functional) for early AMD, intermediate AMD, and geographic atrophy and to evaluate the relevance of these biomarkers for use in future clinical trials.

METHODS

A literature search of PubMed, ScienceDirect, EMBASE, and Web of Science from January 1, 1996 to November 30, 2020 and a patent search were conducted. Search terms included "early AMD," "dry AMD," "intermediate AMD," "biomarkers for nonexudative AMD," "fundus autofluorescence patterns," "color fundus photography," "dark adaptation," and "microperimetry." Articles were assessed for bias and quality with the Mixed-Methods Appraisal Tool. A total of 94 articles were included (61,842 individuals).

RESULTS

Spectral-domain optical coherence tomography was superior at highlighting detailed structural changes in earlier stages of AMD. Fundus autofluorescence patterns were found to be most important in estimating progression of geographic atrophy. Delayed rod intercept time on dark adaptation was the most widely recommended surrogate functional endpoint for early AMD, while retinal sensitivity on microperimetry was most relevant for intermediate AMD. Combinational studies accounting for various patient characteristics and machine/deep-learning approaches were best suited for assessing individualized risk of AMD onset and progression.

CONCLUSION

This systematic review supports the use of structural and functional biomarkers in early AMD and intermediate AMD, which are more reproducible and less invasive than the other classes of biomarkers described. The use of deep learning and combinational algorithms will gain increasing importance in future clinical trials of nonexudative AMD.

Stages of Drusen-Associated Atrophy in Age-Related Macular Degeneration Visible via Histologically Validated Fundus Autofluorescence

PURPOSE

To determine histologic correlates for stages of drusen-associated atrophy observed with fundus autofluorescence (FAF) and color fundus photography (CFP), of eyes with advanced age-related macular degeneration (AMD).

DESIGN

Case study and clinicopathologic correlation.

PARTICIPANT

A white woman with AMD findings of inactive subretinal fibrosis (right eye) and untreated nonexudative type 1 macular neovascularization (left eye) was followed for 9 years before death at 90 years of age.

METHODS

Eyes preserved 6.25 hours after death were postfixed in osmium tannic acid paraphenylenediamine and were prepared for submicrometer epoxy resin sections (115 and 90 from the right and left eye, respectively), with 19 aligned to clinical B-scans. Drusen visible by CFP at the last visit were assigned to 4 stages of FAF: stage 1, isoautofluorescence; stage 2, mildly uniform hyperautofluorescence; stage 3, a ring of hyperautofluorescence around a center of the hypoautofluorescence; and stage 4, uniform hypoautofluorescence.

MAIN OUTCOME MEASURES

Light microscopic morphologic features at known FAF stages, including druse size, druse contents, and changes in overlying retinal pigment epithelium (RPE), photoreceptors, and external limiting membrane (ELM).

RESULTS

Histologic examination of 166 drusen demonstrated that stage 1 isoautofluorescent drusen were visible on CFP. Hyperautofluorescence in stage 2 corresponded to short photoreceptors and complete coverage by RPE. Hypoautofluorescence in stages 3 and 4 corresponded to different extents of RPE atrophy (RPE gap and no RPE, respectively). Of stage 4 drusen, 67% showed no outer nuclear layer (ONL) and an undetectable ELM. Stage 4 included a high proportion of refractile drusen (82%) with many calcific nodules, visible on CFP.

CONCLUSIONS

We present the first direct clinicopathologic correlation for FAF imaging of drusen-associated atrophy. Our data support 4 FAF stages of drusen-associated atrophy. Stage 2 is the earliest detected stage in which loss of screening by photoreceptor photopigment contributes to uniform hyperautofluorescence. Stages 3 and 4 comport with incomplete RPE and outer retinal atrophy as defined by the Classification of Atrophy Meetings group. Loss of RPE, ONL, and ELM in stage 4 indicates that atrophy can begin over individual drusen. Findings will help the identification of new therapeutic approaches and clinical study end points.

Relative Contributions of All-Trans and 11-Cis Retinal to Formation of Lipofuscin and A2E Accumulating in Mouse Retinal Pigment Epithelium

Purpose

Bis-retinoids are a major component of lipofuscin that accumulates in the retinal pigment epithelium (RPE) in aging and age-related macular degeneration (AMD). Although bis-retinoids are known to originate from retinaldehydes required for the light response of photoreceptor cells, the relative contributions of the chromophore, 11-cis retinal, and photoisomerization product, all-trans retinal, are unknown. In photoreceptor outer segments, all-trans retinal, but not 11-cis retinal, is reduced by retinol dehydrogenase 8 (RDH8). Using Rdh8^−/− mice, we evaluated the contribution of increased all-trans retinal to the formation and stability of RPE lipofuscin.

Methods

Rdh8^−/− mice were reared in cyclic-light or darkness for up to 6 months, with selected light-reared cohorts switched to dark-rearing for the final 1 to 8 weeks. The bis-retinoid A2E was measured from chloroform-methanol extracts of RPE-choroid using HPLC-UV/VIS spectroscopy. Lipofuscin fluorescence was measured from whole flattened eyecups (excitation, 488 nm; emission, 565–725 nm).

Results

Cyclic-light-reared Rdh8^−/− mice accumulated A2E and RPE lipofuscin approximately 1.5 times and approximately 2 times faster, respectively, than dark-reared mice. Moving Rdh8^−/− mice from cyclic-light to darkness resulted in A2E levels less than expected to have accumulated before the move.

Conclusions

Our findings establish that elevated levels of all-trans retinal present in cyclic-light-reared Rdh8^−/− mice, which remain low in wild-type mice, contribute only modestly to RPE lipofuscin formation and accumulation. Furthermore, decreases in A2E levels occurring after moving cyclic-light-reared Rdh8^−/− mice to darkness are consistent with processing of A2E within the RPE and the existence of a mechanism that could be a therapeutic target for controlling A2E cytotoxicity.

Intravitreal application of epidermal growth factor in non-exudative age-related macular degeneration

PURPOSE

To assess the safety of intravitreally applied epidermal growth factor (EGF).

METHODS

The clinical interventional, prospective, single-centre, case series study included patients with age-related macular degeneration-related geographic atrophy (GA), in whom the eye with the worse best-corrected visual acuity (BCVA) underwent a single, or repeated, intravitreal injection of EGF (0.75 µg in 50 µL). At baseline and afterwards, the eyes underwent ophthalmological examinations.

RESULTS

The study included seven patients (mean age:70.0±12.2 years (range: 54-86 years), with five patients receiving a single injection and two patients receiving two intravitreal injections in an interval of 4 weeks. Mean duration of follow-up was 97±97 days (median:35 days; range: 7-240 days). Mean BCVA was lower at baseline than at study end (1.41±0.44 logMAR vs 0.97±0.12 logMAR; p=0.03). Mean size of the GA lesions did not differ significantly between baseline and study end (29 212±22 887 pixels vs 29 300±22 905 pixels; p=0.59) nor did the mean perimetric mean defect (-10.3±5.9 dB vs 12.0±8.8 dB; p=0.35) or the electroretinographical b-wave amplitude (44.53±31.7 µV vs 64.5±25.5 µV; p=0.12). After a second injection 4 weeks after the first injection, one of two patients developed a cystoid macular oedema in association with an induced incomplete posterior vitreous detachment. It persisted for 3 weeks. Visual acuity in this eye improved from 1.0 logMAR at baseline to 0.80 logMAR at study end.

CONCLUSIONS

Except for one eye with temporary, self-resolving cystoid macular oedema, single and repeated intravitreal applications of EGF (0.75 µg) in patients with GA did not lead to intraocular inflammations or any observed intraocular side effect.

TRIAL REGISTRATION NUMBER

ISRCTN12733334.

Impact of Baseline Characteristics on Geographic Atrophy Progression in the FILLY Trial Evaluating the Complement C3 Inhibitor Pegcetacoplan

PURPOSE

To evaluate the effect of select baseline characteristics on geographic atrophy (GA) progression in eyes receiving intravitreal pegcetacoplan or sham.

DESIGN

Phase 2 multicenter, randomized, single-masked, sham-controlled trial.

METHODS

Patients with GA received 15 mg pegcetacoplan monthly or every other month (EOM), or sham injection monthly or EOM for 12 months. Primary efficacy endpoint was change in GA lesion size (square root) from baseline. Post hoc analysis evaluated the effects of age; gender; lesion size, focality, and location (extrafoveal vs foveal); pseudodrusen status; best-corrected visual acuity (BCVA); and low-luminance deficit (LLD) on GA progression at Month 12.

RESULTS

Of 246 randomized patients, 192 with 12-month data were included in this analysis. Overall mean (standard deviation) change in lesion size (mm) was 0.26 (0.17) (P < .01), 0.27 (0.27) (P < .05), and 0.36 (0.21) in the monthly pegcetacoplan (n = 67), EOM pegcetacoplan (n = 58), and sham (n = 67) groups, respectively. In univariate analysis, patients with extrafoveal lesions (P < .001), BCVA ≥20/60 (P = .001), and larger LLD (P = .002) had greater mean changes in lesion size. Multivariate analysis confirmed significant association of extrafoveal lesions (P = .001) and larger LLD (P = .023) with GA progression. Monthly and EOM pegcetacoplan significantly reduced progression (P < .05) when controlling for these risk factors.

CONCLUSIONS

Extrafoveal lesions and larger LLD are potential risk factors for GA progression. Pegcetacoplan treatment significantly controlled GA progression even after accounting for these risk factors.

Rational Alteration of Pharmacokinetics of Chiral Fluorinated and Deuterated Derivatives of Emixustat for Retinal Therapy

Recycling of all-trans-retinal to 11-cis-retinal through the visual cycle is a fundamental metabolic pathway in the eye. A potent retinoid isomerase (RPE65) inhibitor, (R)-emixustat, has been developed and tested in several clinical trials; however, it has not received regulatory approval for use in any specific retinopathy. Rapid clearance of this drug presents challenges to maintaining concentrations in eyes within a therapeutic window. To address this pharmacokinetic inadequacy, we rationally designed and synthesized a series of emixustat derivatives with strategically placed fluorine and deuterium atoms to slow down the key metabolic transformations known for emixustat. Crystal structures and quantum chemical analysis of RPE65 in complex with the most potent emixustat derivatives revealed the structural and electronic bases for how fluoro substituents can be favorably accommodated within the active site pocket of RPE65. We found a close (∼3.0 Å) F-π interaction that is predicted to contribute ∼2.4 kcal/mol to the overall binding energy.

Pathogenic mechanisms contributing to the vulnerability of aging human photoreceptor cells

In human retina, photoreceptor cell death (PCD) is a slow but conspicuous event, which continues with aging. Rods die earlier than cones, the latter continue to alter in a subtle manner until advanced aging. This review summarizes the existing information on age-related changes in photoreceptor cells, especially cones and analyses the possible associated factors. Oxidative and nitrosative stress are involved in photoreceptor alterations, which may stem from light and iron toxicity and other sources. Lipid peroxidation in macular photoreceptor outer segments and mitochondrial aberrations are prominent in aging. It is important to understand how those changes ultimately trigger PCD. The redistribution of calbindin D-28K and long/middle-wavelength-sensitive opsin in the parafoveal and perifoveal cones, anomalies in their somata and axons are strong predictors of their increasing vulnerability with aging. Signs of reduced autophagy, with autophagosomes containing organelle remnants are seen in aging photoreceptor cells. Currently, mechanisms that lead to human PCD are unknown; some observations favour apoptosis as a pathway. Since cones appear to change slowly, there is an opportunity to reverse those changes before they die. Therefore, a full understanding of how cones alter and the molecular pathways they utilize for survival must be the future research goal. Recent approaches to prevent PCD in aging and diseases are highlighted.