Prevalence of Subretinal Drusenoid Deposits in Older Persons with and without Age-Related Macular Degeneration, by Multimodal Imaging

RETICULAR PSEUDODRUSEN DISAPPEARANCE AFTER DEVELOPMENT OF MACULAR NEOVASCULARIZATION

PURPOSE

To explore changes in reticular pseudodrusen (RPD) number and location after the development of macular neovascularization (MNV) in eyes with prior intermediate age-related macular degeneration, focusing on different retinal regions differently affected by MNV.

METHODS

This retrospective longitudinal study included intermediate age-related macular degeneration eyes with RPD that developed MNV. Reticular pseudodrusen were assessed at baseline when MNV was diagnosed (MNV stage) and after anti-vascular endothelial growth factor treatment. Three regions of interest were considered: MNV area, subretinal fluid (SRF) area, and a marginal area of 1,000 µm around SRF (marginal zone). Reticular pseudodrusen counts were compared with age- and sex-matched control eyes with RPD that did not develop MNV.

RESULTS

Reticular pseudodrusen number exhibited a significant decrease after MNV development in the MNV area (P = 0.048) and in the area with SRF (P = 0.078). A statistically significant decrease was also disclosed in the marginal area around SRF (P = 0.002), associated with larger SRF areas. Control eyes did not show any significant change in the RPD count.

CONCLUSION

Reticular pseudodrusen reduction after MNV development suggests a complex interplay involving the MNV itself, the presence of SRF, and trophic changes. The results of this study highlight the role of MNV in retinal nutritional balance and provide intriguing results in the RPD life cycle.

Extent and Topography of Subretinal Drusenoid Deposits Associate With Rod-Mediated Vision in Aging and AMD: ALSTAR2 Baseline

Purpose

In AMD, rod-mediated dark adaptation (RMDA) at 5° eccentricity is slower in eyes with subretinal drusenoid deposits (SDDs) than in eyes without. Here we quantified SDD burden using supervised deep learning for comparison to vision and photoreceptor topography.

Methods

In persons ≥60 years from the Alabama Study on Early Age-Related Macular Degeneration 2, normal, early AMD, and intermediate AMD eyes were classified by the AREDS nine-step system. A convolutional neural network was trained on 55°-wide near-infrared reflectance images for SDD segmentation. Trained graders annotated ground truth (SDD yes/no). Predicted and true datasets agreed (Dice coefficient, 0.92). Inference was manually proofread using optical coherence tomography. The mean SDD area (mm2) was compared among diagnostic groups (linear regression) and to vision (age-adjusted Spearman correlations). Fundus autofluorescence images were used to mask large vessels in SDD maps.

Results

In 428 eyes of 428 persons (normal, 218; early AMD, 120; intermediate AMD, 90), the mean SDD area differed by AMD severity (P < 0.0001): 0.16 ± 0.87 (normal), 2.48 ± 11.23 (early AMD), 11.97 ± 13.33 (intermediate AMD). Greater SDD area was associated with worse RMDA (r = 0.27; P < 0.0001), mesopic (r = -0.13; P = 0.02) and scotopic sensitivity (r = -0.17; P < 0.001). SDD topography peaked at 5° superior, extended beyond the Early Treatment of Diabetic Retinopathy Study grid and optic nerve, then decreased.

Conclusions

SDD area is associated with degraded rod-mediated vision. RMDA 5° (superior retina) probes where SDD is maximal, closer to the foveal center than the rod peak at 3 to 6 mm (10.4°-20.8°) superior and the further eccentric peak of rod:cone ratio. Topographic data imply that factors in addition to rod density influence SDD formation.

The potential key role of choroidal non-perfusion and rod degeneration in the pathogenesis of macular neovascularization type 3

Macular neovascularization type 3 (MNV3) is a multifactorial disease with distinct epidemiological, clinical, pathomorphological and topographical characteristics. This review of the literature discusses the latest experimental and clinical outcomes that could explain the pathogenesis of retinal neovascularization. Although patients with MNV3 are usually older than those with MNV1 or 2, their lesions do not coexist with, precede, or follow other types in the same eye. The regional distribution of MNV3 lesions is characterized as confined to the parafoveal macula without any involvement of the rod-free foveal area. Focal outer retinal atrophy and choroidal non-perfusion are the main structural features that occur prior to the development of retinal neovascularization. Also, histological and experimental studies of MNV3 and other non-neovascular age-related macular degeneration diseases complicated with MNV3-like lesions strongly suggest rod degeneration contributes to the pathogenesis. Therefore, the retinal neovascularization in MNV3 has a different pathogenesis from the choroidal neovascularization in MNV1 and 2 and emerging evidence indicates that choroidal non-prefusion and rod degeneration play a key role in the pathogenesis of MNV3. Accordingly, we suggest a sequence of pathological events that start with choroidal non-perfusion due to advanced age followed by hypoxia of the outer retina at the parafoveal area. This induces a remarkable degeneration of rods that triggers the growth of retinal neovascularization due to the imbalance of the angiogenic factors in the outer retina.

Prominin-1 null Xenopus laevis develop subretinal drusenoid-like deposits, cone-rod dystrophy, and RPE atrophy

Mutations in the PROMININ-1 (PROM1) gene are associated with inherited, non-syndromic vision loss. Here, we used CRISPR/Cas9 to induce truncating prom1-null mutations in Xenopus laevis to create a disease model. We then tracked progression of retinal degeneration in these animals from the ages of 6 weeks to 3 years old. We found that retinal degeneration caused by prom1-null is age-dependent and likely involves death or damage to the retinal pigment epithelium (RPE) that precedes photoreceptor degeneration. As prom1-null frogs age, they develop large cellular debris deposits in the subretinal space and outer segment layer which resemble subretinal drusenoid deposits (SDD) in their location, histology, and representation in color fundus photography and optical coherence tomography (OCT). In older frogs, these SDD-like deposits accumulate in size and number, and they are present before retinal degeneration occurs. Evidence for an RPE origin of these deposits includes infiltration of pigment granules into the deposits, thinning of RPE as measured by OCT, and RPE disorganization as measured by histology and OCT. The appearance and accumulation of SDD-like deposits and RPE thinning and disorganization in our animal model suggests an underlying disease mechanism for prom1-null mediated blindness of death and dysfunction of the RPE preceding photoreceptor degeneration, instead of direct effects upon photoreceptor outer segment morphogenesis, as was previously hypothesized.

Probing Deposit-Driven Age-Related Macular Degeneration Via Thicknesses of Outer Retinal Bands and Choroid: ALSTAR2 Baseline

Purpose

We aimed to identify structural differences in normal eyes, early age-related macular degeneration (AMD), and intermediate AMD eyes using optical coherence tomography (OCT) in a well-characterized, large cross-sectional cohort.

Methods

Subjects ≥ 60 years with healthy normal eyes, as well as early or intermediate AMD were enrolled in the Alabama Study on Age-related Macular Degeneration 2 (ALSTAR2; NCT04112667). Using Spectralis HRA + OCT2, we obtained macular volumes for each participant. An auto-segmentation software was used to segment six layers and sublayers: photoreceptor inner and outer segments, subretinal drusenoid deposits (SDDs), retinal pigment epithelium + basal lamina (RPE + BL), drusen, and choroid. After manually refining the segmentations of all B-scans, mean thicknesses in whole, central, inner and outer rings of the ETDRS grid were calculated and compared among groups.

Results

This study involved 502 patients, 252 were healthy, 147 had early AMD, and 103 had intermediate AMD eyes (per Age-Related Eye Disease Study [AREDS] 9-step). Intermediate AMD eyes exhibited thicker SDD and drusen, thinner photoreceptor inner segments, and RPE compared to healthy and early AMD eyes. They also had thicker photoreceptor outer segments than early AMD eyes. Early AMD eyes had thinner photoreceptor outer segments than normal eyes but a thicker choroid than intermediate AMD eyes. Using the Beckman scale, 42% of the eyes initially classified as early AMD shifted to intermediate AMD, making thickness differences for photoreceptor outer segments and choroid insignificant.

Conclusions

With AMD stages, the most consistent structural differences involve appearance of drusen and SDD, followed by RPE + BL thickness, and then thickness of photoreceptor inner and outer segments. Structural changes in the transition from aging to intermediate AMD include alterations in the outer retinal bands, including the appearance of deposits on either side of the RPE.

Non-Neovascular Age-Related Macular Degeneration Assessment: Focus on Optical Coherence Tomography Biomarkers

The imagistic evaluation of non-neovascular age-related macular degeneration (AMD) is crucial for diagnosis, monitoring progression, and guiding management of the disease. Dry AMD, characterized primarily by the presence of drusen and retinal pigment epithelium atrophy, requires detailed visualization of the retinal structure to assess its severity and progression. Several imaging modalities are pivotal in the evaluation of non-neovascular AMD, including optical coherence tomography, fundus autofluorescence, or color fundus photography. In the context of emerging therapies for geographic atrophy, like pegcetacoplan, it is critical to establish the baseline status of the disease, monitor the development and expansion of geographic atrophy, and to evaluate the retina's response to potential treatments in clinical trials. The present review, while initially providing a comprehensive description of the pathophysiology involved in AMD, aims to offer an overview of the imaging modalities employed in the evaluation of non-neovascular AMD. Special emphasis is placed on the assessment of progression biomarkers as discerned through optical coherence tomography. As the landscape of AMD treatment continues to evolve, advanced imaging techniques will remain at the forefront, enabling clinicians to offer the most effective and tailored treatments to their patients.

Ferroptosis as a potential therapeutic target for age-related macular degeneration

Cell death plays a crucial part in the process of age-related macular degeneration (AMD), but its mechanisms remain elusive. Accumulating evidence suggests that ferroptosis, a novel form of regulatory cell death characterized by iron-dependent accumulation of lipid hydroperoxides, has a crucial role in the pathogenesis of AMD. Numerous studies have suggested that ferroptosis participates in the degradation of retinal cells and accelerates the progression of AMD. Furthermore, inhibitors of ferroptosis exhibit notable protective effects in AMD, underscoring the significance of ferroptosis as a pivotal mechanism in the death of retinal cells during the process of AMD. This review aims to summarize the molecular mechanisms of ferroptosis in AMD, enumerate potential inhibitors and discuss the challenges and future opportunities associated with targeting ferroptosis as a therapeutic strategy, providing important information references and insights for the prevention and treatment of AMD.

Association between Subretinal Drusenoid Deposits and Age-Related Macular Degeneration in Multimodal Retinal Imaging

Multimodal retinal imaging enables the detection of subretinal drusenoid deposits (SDD) with significantly greater accuracy compared to fundus photography. The study aimed to analyze a relationship between the presence of SDD, the clinical picture of AMD, and disease progression in a 3 year follow-up. A total of 602 eyes of 339 patients with a diagnosis of AMD, of which 121 (55%) had SDD confirmed in multimodal retinal imaging, were enrolled in the study. SDD was related to a more advanced stage of AMD (p = 0.008), especially with the presence of geographic atrophy (OR = 4.11, 95% CI 2.02-8.38, p < 0.001). Eyes with SDD presented significantly lower choroidal and retinal thickness (ATC: 210.5 μm, CRT: 277 μm, respectively) and volume (AVC: 0.17 mm3, CRV: 8.29 mm3, p < 0.001, respectively) compared to SDD-negative eyes (ATC: 203 μm, CRT: 277 μm; AVC: 7.08 mm3, 8.54 mm3, p < 0.001). Accordingly, the prevalence of pachychoroids and pachyvessels was significantly lower in the SDD present group than in eyes without SDD (p = 0.004; p = 0.04, respectively). Neither demographic factors, lipid profile, genetic predisposition, systemic vascular disease comorbidities, nor parameters of retinal vessels were affected by the presence of SDD. We found no effect of SDD presence on AMD progression (p = 0.12). The presence of SDD appeared to be related to local rather than systemic factors.

Epidemiology of geographic atrophy and its precursor features of intermediate age-related macular degeneration

Globally age-related macular degeneration (AMD) is a leading cause of blindness with a significant impact on quality of life. Geographic atrophy (GA) is the atrophic late form of AMD and its prevalence increases markedly with age with around 1 in 5 persons aged 85 and above having GA in at least one eye. Bilateral GA leads to severe visual impairment thus posing a significant burden on patients, careers and health providers. The incidence and prevalence of GA varies across different geographic regions, with the highest rates in those of European ancestry. Although heterogeneity in definitions of GA and reporting strategy can explain some of the discrepancies, the data overall are consistent in showing a lower prevalence in other ethnicities such as those of Asian heritage. This is at present unexplained but thought to be due to the existence of protective factors such as differences in eye pigmentation, diet, environmental exposures and genetic variability. This review covers key aspects of the prevalence and incidence of the ocular precursor features of GA (large drusen, pigmentary abnormalities and reticular pseudo-drusen), the late stage of GA and factors that have been known to be associated with modifying risk including systemic, demographic, environment, genetic and ocular. Understanding the global epidemiology scenario is crucial for the prevention of and management of patients with GA.

Reticular Pseudodrusen: Interreader Agreement of Evaluation on OCT Imaging in Age-Related Macular Degeneration

Purpose

To determine the interreader agreement for reticular pseudodrusen (RPD) assessment on combined infrared reflectance (IR) and OCT imaging in the early stages of age-related macular degeneration across a range of different criteria to define their presence.

Design

Interreader agreement study.

Participants

Twelve readers from 6 reading centers.

Methods

All readers evaluated 100 eyes from individuals with bilateral large drusen for the following: (1) the presence of RPD across a range of different criteria and (2) the number of Stage 2 or 3 RPD lesions (from 0 to ≥ 5 lesions) on an entire OCT volume scan and on a selected OCT B-scan. Supportive information was available from the corresponding IR image.

Main Outcome Measures

Interreader agreement, as assessed by Gwet's first-order agreement coefficient (AC₁).

Results

When evaluating an entire OCT volume scan, there was substantial interreader agreement for the presence of any RPD, any or ≥ 5 Stage 2 or 3 lesions, and ≥ 5 definite lesions on en face IR images corresponding to Stage 2 or 3 lesions (AC₁ = 0.60-0.72). On selected OCT B-scans, there was also moderate-to-substantial agreement for the presence of any RPD, any or ≥ 5 Stage 2 or 3 lesions (AC₁ = 0.58-0.65) and increasing levels of agreement with increasing RPD stage (AC₁ = 0.08, 0.56, 0.78, and 0.99 for the presence of any Stage 1, 2, 3, and 4 lesions, respectively). There was substantial agreement regarding the number of Stage 2 or 3 lesions on an entire OCT volume scan (AC₁ = 0.68), but only fair agreement for this evaluation on selected B-scans (AC₁ = 0.30).

Conclusions

There was generally substantial or near-substantial-but not near-perfect-agreement for assessing the presence of RPD on entire OCT volume scans or selected B-scans across a range of differing RPD criteria. These findings underscore how interreader variability would likely contribute to the variability of findings related to the clinical associations of RPD. The low levels of agreement for assessing RPD number on OCT B-scans underscore the likely challenges of quantifying RPD extent with manual grading.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Lysolipids are prominent in subretinal drusenoid deposits, a high-risk phenotype in age-related macular degeneration

Introduction

Age related macular degeneration (AMD) causes legal blindness worldwide, with few therapeutic targets in early disease and no treatments for 80% of cases. Extracellular deposits, including drusen and subretinal drusenoid deposits (SDD; also called reticular pseudodrusen), disrupt cone and rod photoreceptor functions and strongly confer risk for advanced disease. Due to the differential cholesterol composition of drusen and SDD, lipid transfer and cycling between photoreceptors and support cells are candidate dysregulated pathways leading to deposit formation. The current study explores this hypothesis through a comprehensive lipid compositional analysis of SDD.

Methods

Histology and transmission electron microscopy were used to characterize the morphology of SDD. Highly sensitive tools of imaging mass spectrometry (IMS) and nano liquid chromatography tandem mass spectrometry (nLC-MS/MS) in positive and negative ion modes were used to spatially map and identify SDD lipids, respectively. An interpretable supervised machine learning approach was utilized to compare the lipid composition of SDD to regions of uninvolved retina across 1873 IMS features and to automatically discern candidate markers for SDD. Immunohistochemistry (IHC) was used to localize secretory phospholipase A2 group 5 (PLA2G5).

Results

Among the 1873 detected features in IMS data, three lipid classes, including lysophosphatidylcholine (LysoPC), lysophosphatidylethanolamine (LysoPE) and lysophosphatidic acid (LysoPA) were observed nearly exclusively in SDD while presumed precursors, including phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidic acid (PA) lipids were detected in SDD and adjacent photoreceptor outer segments. Molecular signals specific to SDD were found in central retina and elsewhere. IHC results indicated abundant PLA2G5 in photoreceptors and retinal pigment epithelium (RPE).

Discussion

The abundance of lysolipids in SDD implicates lipid remodeling or degradation in deposit formation, consistent with ultrastructural evidence of electron dense lipid-containing structures distinct from photoreceptor outer segment disks and immunolocalization of secretory PLA2G5 in photoreceptors and RPE. Further studies are required to understand the role of lipid signals observed in and around SDD.

Prevalence and risk factors for age-related macular degeneration in a population-based cohort study of older adults in Northern Ireland using multimodal imaging: NICOLA Study

PURPOSE

To report prevalence and risk factor associations for age-related macular degeneration (AMD) and AMD features from multimodal retinal grading in a multidisciplinary longitudinal population-based study of aging in Northern Ireland.

STUDY DESIGN

Population-based longitudinal cohort study.

METHODS

Retinal imaging at the Norther Ireland Cohort for the Longitudinal Aging Study health assessment included stereo Colour Fundus Photography (CFP) (Canon CX-1, Tokyo, Japan) and Spectral-Domain Optical Coherence Tomography (SD-OCT) ((Heidelberg Retinal Angopgraph (HRA)+OCT; Heidelberg Engineering, Heidelberg, Germany). Medical history and demographic information was obtained during a home interview. Descriptive statistics were used to describe the prevalence of AMD and individual AMD features. Multiple imputation followed by multiple regression modelling was used to explore risk factor associations including relationships with AMD genetic risk score.

RESULTS

Retinal images from 3386 participants were available for analysis. Mean age of the sample was 63.4 (SD 9.01, range: 36-99). Population weighted prevalence of AMD using colour grading in those over 55 years was: no drusen: 6 0.4%; drusen <63 μm: 15.9%; drusen 63-125 µm: 13.7%; drusen >125 µm or pigmentary changes: 8.3%; late AMD: 1.6%. Prevalence of AMD features in those over 55 years was: OCT drusen 27.5%, complete outer retinal pigment epithelium and outer retinal atrophy (cRORA) on OCT was 4.3%, reticular drusen 3.2% and subretinal drusenoid deposits 25.7%. The genetic risk score was significantly associated with drusen and cRORA but less so for SDD alone and non-significant for hyperpigmentation or vitelliform lesions.

CONCLUSIONS

Multimodal imaging-based classification has provided evidence of some divergence of genetic risk associations between classical drusen and SDD. Our findings support an urgent review of current AMD severity classification systems.

Single-cell RNA sequencing in dissecting microenvironment of age-related macular degeneration: Challenges and perspectives

Age-related macular degeneration (AMD) is the leading cause of blindness in individuals over the age of 50 years, yet its etiology and pathogenesis largely remain uncovered. Single-cell RNA sequencing (scRNA-seq) technologies are recently developed and have a number of advantages over conventional bulk RNA sequencing techniques in uncovering the heterogeneity of complex microenvironments containing numerous cell types and cell communications during various biological processes. In this review, we summarize the latest discovered cellular components and regulatory mechanisms during AMD development revealed by scRNA-seq. In addition, we discuss the main challenges and future directions in exploring the pathophysiology of AMD equipped with single-cell technologies. Our review underscores the importance of multimodal single-cell platforms (such as single-cell spatiotemporal multi-omics and single-cell exosome omics) as new approaches for basic and clinical AMD research in identifying biomarker, characterizing cellular responses to drug treatment and environmental stimulation.

Assessment of the Classification of Age-Related Macular Degeneration Severity from the Northern Ireland Sensory Ageing Study Using a Measure of Dark Adaptation

Purpose

To assess the differences in rod-mediated dark adaptation (RMDA) between different grades of age-related macular degeneration (AMD) severity using an OCT-based criterion compared with those of AMD severity using the Beckman color fundus photography (CFP)-based classification and to assess the association between the presence of subretinal drusenoid deposits (SDDs) and RMDA at different grades of AMD severity using an OCT-based classification.

Design

Cross-sectional study.

Participants

Participants from the Northern Ireland Sensory Ageing study (Queen's University Belfast).

Methods

Complete RMDA (rod-intercept time [RIT]) data, CFP, and spectral-domain OCT images were extracted. Participants were stratified into 4 Beckman groups (omitting late-stage AMD) and 3 OCT-based groups. The presence and stage of SDDs were identified using OCT.

Main Outcome Measures

Rod-intercept time data (age-corrected).

Results

Data from 459 participants (median [interquartile range] age, 65 [59-71] years) were stratified by both the classifications. Subretinal drusenoid deposits were detected in 109 eyes. The median (interquartile range) RMDA for the Beckman classification (Beckman 0-3, with 3 being intermediate age-related macular degeneration [iAMD]) groups was 6.0 (4.5-8.7), 6.6 (4.7-10.5), 5.7 (4.4-7.4), and 13.2 (6-21.1) minutes, respectively. OCT classifications OCT0-OCT2 yielded different median (interquartile range) values: 5.8 (4.5-8.5), 8.4 (5.2-13.3), and 11.1 (5.3-20.1) minutes, respectively. After correcting for age, eyes in Beckman 3 (iAMD) had statistically significantly worse RMDA than eyes in the other Beckman groups (P ≤ 0.005 for all), with no statistically significant differences between the other Beckman groups. Similarly, after age correction, eyes in OCT2 had worse RMDA than eyes in OCT0 (P ≤ 0.001) and OCT1 (P < 0.01); however, there was no statistically significant difference between eyes in OCT0 and eyes in OCT1 (P = 0.195). The presence of SDDs was associated with worse RMDA in OCT2 (P < 0.01) but not in OCT1 (P = 0.285).

Conclusions

Eyes with a structural definition of iAMD have delayed RMDA, regardless of whether a CFP- or OCT-based criterion is used. In this study, after correcting for age, the RMDA did not differ between groups of eyes defined to have early AMD or normal aging, regardless of the classification. The presence of SDDs has some effect on RMDA at different grades of AMD severity.

How Vision Is Impaired From Aging to Early and Intermediate Age-Related Macular Degeneration: Insights From ALSTAR2 Baseline

Purpose

We hypothesize the first visual dysfunction in transitioning to early and intermediate age-related macular degeneration (AMD) is delayed rod-mediated dark adaptation (RMDA), owing to impaired photoreceptor sustenance from the circulation. This analysis from the Alabama Study on Early Age-related Macular Degeneration 2 provides insight on our framework's validity, comparing RMDA and other visual tests among older normal, early, and intermediate AMD eyes.

Methods

AMD disease severity was determined via fundus photos using the Age-Related Eye Disease Study nine-step system. Visual functions evaluated were RMDA 5°, acuity, contrast sensitivity (photopic, mesopic), and light sensitivity for a macular grid (scotopic, mesopic, photopic). Presence versus absence of subretinal drusenoid deposits (SDD) was identified through multimodal imaging.

Results

One eye from each of 481 persons (mean age, 72 years) was evaluated. All visual functions were significantly worse with increasing AMD disease severity. Using z-scores to standardize visual function measures across groups, the greatest difference in probability density functions between older normal and intermediate AMD was for RMDA. Early and intermediate AMD eyes with SDD present had longer rod intercept times than eyes with SDD absent. SDD absent eyes also exhibited delayed RMDA and wide probability density functions relative to normal eyes.

Conclusions

Among the visual functions evaluated, RMDA best discriminates among normal, early AMD, and intermediate AMD eyes. The Alabama Study on Early Age-related Macular Degeneration 2 will evaluate whether AMD's natural history confirms our hypothesis at the 3-year follow-up.

Translational Relevance

Results support a sequence of visual function impairments in aging and AMD, suggesting RMDA as a promising outcome for evaluating interventions in early disease.

Age-related macular degeneration eyes presenting with cuticular drusen and reticular pseudodrusen

This study aimed to describe the clinical characteristics of age-related macular degeneration (AMD) eyes with both cuticular drusen (CD) and reticular pseudodrusen (RPD). Clinical records of patients diagnosed with CD or RPD with multimodal imaging was reviewed for patients diagnosed with both CD and RPD. The distribution patterns of CD (macular and diffuse type) and RPD (localized, intermediate, and diffuse type), presence of soft drusen, large drusen (> 200 µm), variant subretinal drusenoid deposits, and macular complications were investigated. Of the 220 eyes of 110 patients diagnosed with CD and 926 eyes of 463 patients diagnosed with RPD, 13 eyes of seven patients met the diagnostic criteria for both CD and RPD. The mean age at initial presentation was 71.4 ± 8.8 years and six patients were female. The mean subfoveal choroidal thickness was 143.8 ± 25.1 µm. The distribution of CD was of the macular type in all eyes. Distribution of RPD was localized in 11 eyes (84.6%) and intermediate in two eyes (15.4%). Soft drusen, large drusen, and variant subretinal drusenoid deposits were present in 13 (100%), 12 (92.3%) and, seven (53.8%) eyes, respectively. Macular neovascularization was observed in two eyes (15.4%). CD and RPD can coexist in eyes with AMD. Multimodal imaging should be used for AMD eyes with features suggestive of CD and RPD, considering the high likelihood of developing late AMD.

SD-OCT Biomarkers and the Current Status of Artificial Intelligence in Predicting Progression from Intermediate to Advanced AMD

Age-related macular degeneration (AMD) is one of the leading causes of blindness in the Western World. Optical coherence tomography (OCT) has revolutionized the diagnosis and follow-up of AMD patients. This review focuses on SD-OCT imaging biomarkers which were identified as predictors for progression in intermediate AMD to late AMD, either geographic atrophy (GA) or choroidal neovascularization (CNV). Structural OCT remains the most compelling modality to study AMD features related to the progression such as drusen characteristics, hyperreflective foci (HRF), reticular pseudo-drusen (RPD), sub-RPE hyper-reflective columns and their impact on retinal layers. Further on, we reviewed articles that attempted to integrate biomarkers that have already proven their involvement in intermediate AMD progression, in their models of artificial intelligence (AI). By combining structural biomarkers with genetic risk and lifestyle the predictive ability becomes more accurate.

Subretinal drusenoid deposits: An update

A wide spectrum of phenotypic manifestations characterizes age-related macular degeneration (AMD). Drusen is considered the hallmark of AMD and is located underneath the retinal pigment epithelium (RPE). In contrast, subretinal drusenoid deposits (SDDs), also known as reticular pseudodrusens, are located in the subretinal space, on top of the RPE. SDDs are poorly detected by clinical examination and color fundus photography. Multimodal imaging is required for their proper diagnosis. SDDs are topographically and functionally related to rods. SDDs cause a deep impairment in retinal sensitivity and dark adaptation. SDDs are dynamic structures that may grow, fuse with each other, or regress over time. An intermediate step in some eyes is the development of an acquired vitelliform lesion. The presence of SDD confers an eye a high risk for the development of late AMD. SDD leads to macular neovascularization, particularly type 3, geographic atrophy, and outer retinal atrophy.

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.

Reticular Pseudodrusen in Late-Onset Retinal Degeneration

PURPOSE

To characterize the association of reticular pseudodrusen (RPD) with late-onset retinal degeneration (L-ORD) using multimodal imaging.

DESIGN

Prospective, 2-center, longitudinal case series.

PARTICIPANTS

Twenty-nine patients with L-ORD.

METHODS

All patients were evaluated within a 3-year interval with near-infrared reflectance, fundus autofluorescence, and spectral-domain OCT. In addition, a subset of patients also underwent indocyanine green angiography, fundus fluorescein angiography, mesopic microperimetry, and multifocal electroretinography.

MAIN OUTCOME MEASURES

Prevalence, topographic distribution, and temporal phenotypic changes of RPD in L-ORD.

RESULTS

A total of 29 patients with molecularly confirmed L-ORD were included in this prospective study. Reticular pseudodrusen was detected in 18 patients (62%) at baseline, 10 of whom were men. The prevalence of RPD varied with age. The mean age of RPD patients was 57.3 ± 7.2 years. Reticular pseudodrusen was not seen in patients younger than the fifth decade of life (n = 3 patients) or in the eighth decade of life (n = 5 patients). Reticular pseudodrusen were found commonly in the macula with relative sparing of the fovea and also were identified in the peripheral retina. The morphologic features of RPD changed with follow-up. Two patients (3 eyes) demonstrated RPD regression.

CONCLUSIONS

Reticular pseudodrusen is found frequently in patients with L-ORD and at a younger age than in individuals with age-related macular degeneration (AMD). Reticular pseudodrusen exhibits quick formation and collapse, change in type and morphologic features with time, and relative foveal sparing and also has a peripheral retinal location in L-ORD.

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.

Topographic Distribution and Progression of Soft Drusen Volume in Age-Related Macular Degeneration Implicate Neurobiology of Fovea

Purpose

To refine estimates of macular soft drusen abundance in eyes with age-related macular degeneration (AMD) and evaluate hypotheses about drusen biogenesis, we investigated topographic distribution and growth rates of drusen by optical coherence tomography (OCT). We compared results to retinal features with similar topographies (cone density and macular pigment) in healthy eyes.

Methods

In a prospective study, distribution and growth rates of soft drusen in eyes with AMD were identified by human observers in OCT volumes and analyzed with computer-assistance. Published histologic data for macular cone densities (n = 12 eyes) and in vivo macular pigment optical density (MPOD) measurements in older adults with unremarkable maculae (n = 31; 62 paired eyes, averaged) were revisited. All values were normalized to Early Treatment Diabetic Retinopathy Study (ETDRS) subfield areas.

Results

Sixty-two eyes of 44 patients were imaged for periods up to 78 months. Soft drusen volume per unit volume at baseline is 24.6-fold and 2.3-fold higher in the central ETDRS subfield than in outer and inner rings, respectively, and grows most prominently there. Corresponding ratios (central versus inner and central versus outer) for cone density in donor eyes is 13.3-fold and 5.1-fold and for MPOD, 24.6 and 23.9-fold, and 3.6 and 3.6-fold.

Conclusions

Normalized soft drusen volume in AMD eyes as assessed by OCT is ≥ 20-fold higher in central ETDRS subfields than in outer rings, paralleling MPOD distribution in healthy eyes. Data on drusen volume support this metric for AMD risk assessment and clinical trial outcome measure. Alignment of different data modalities support the ETDRS grid for standardizing retinal topography in mechanistic studies of drusen biogenesis.

SUBRETINAL DRUSENOID DEPOSIT IN AGE-RELATED MACULAR DEGENERATION: Histologic Insights Into Initiation, Progression to Atrophy, and Imaging

PURPOSE

To clarify the role of subretinal drusenoid deposits (SDD; pseudodrusen) in the progression of age-related macular degeneration through high-resolution histology.

METHODS

In 33 eyes of 32 donors (early age-related macular degeneration, n = 15; geographic atrophy, n = 9; neovascular age-related macular degeneration, n = 7; unremarkable, n = 2), and 2 eyes of 2 donors with in vivo multimodal imaging including optical coherence tomography, examples of SDD contacting photoreceptors were assessed.

RESULTS

Subretinal drusenoid deposits were granular extracellular deposits at the apical retinal pigment epithelium (RPE); the smallest were 4-µm wide. Outer segment (OS) fragments and RPE organelles appeared in some larger deposits. A continuum of photoreceptor degeneration included OS disruption, intrusion into inner segments, and disturbance of neurosensory retina. In a transition to outer retinal atrophy, SDD appeared to shrink, OS disappeared, inner segment shortened, and the outer nuclear layer thinned and became gliotic. Stage 1 SDD on optical coherence tomography correlated with displaced OS. Confluent and disintegrating Stage 2 to 3 SDD on optical coherence tomography and dot pseudodrusen by color fundus photography correlated with confluent deposits and ectopic RPE.

CONCLUSION

Subretinal drusenoid deposits may start at the RPE as granular, extracellular deposits. Photoreceptor OS, RPE organelles, and cell bodies may appear in some advanced deposits. A progression to atrophy associated with deposit diminution was confirmed. Findings support a biogenesis hypothesis of outer retinal lipid cycling.

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.

Biometrics, Impact, and Significance of Basal Linear Deposit and Subretinal Drusenoid Deposit in Age-Related Macular Degeneration

Purpose

Basal linear deposit (BLinD) is a thin layer of soft drusen material. To elucidate the biology of extracellular deposits conferring age-related macular degeneration (AMD) progression risk and inform multimodal clinical imaging based on optical coherence tomography (OCT), we examined lipid content and regional prevalence of BLinD, soft drusen, pre-BLinD, and subretinal drusenoid deposit (SDD) in AMD and non-AMD aged eyes. We estimated BLinD volume and illustrated its relation to type 1 macular neovascularization (MNV).

Methods

Donor eyes were classified as early to intermediate AMD (n = 25) and age-matched controls (n = 54). In high-resolution histology, we assessed BLinD/soft drusen thickness at 836 and 1716 locations in AMD and control eyes, respectively. BLinD volume was estimated using solid geometry in donor eyes, one clinically characterized.

Results

BLinD, drusen, type 1 MNV, and fluid occupy the sub-RPE-basal laminar space. BLinD volume in a 3-mm diameter circle may be as much as 0.0315 mm3. Osmophilic lipid was more concentrated in BLinD/drusen than SDD. In the fovea, BLinD/drusen was prevalent in AMD eyes; pre-BLinD was prevalent in control eyes. SDD was low in the fovea and high in perifovea, especially in AMD eyes.

Conclusions

Although invisible, BLinD may presage type 1 MNV. BLinD volume approaches the criterion OCT drusen volume of 0.03 mm3 for AMD progression risk. BLinD culminates years of subfoveal lipid accumulation. SDD is detected relatively late in life, with currently unknown precursors. Deposit topography suggests one outer retinal lipid recycling system serving specialized cone and rod physiology, and its dysregulation in AMD is due to impaired transfer to the circulation.

Association of Drusen Phenotype in Age-Related Macular Degeneration from Human Eye-Bank Eyes to Disease Stage and Cause of Death

PURPOSE

To stage maculopathy, assess and quantify drusen, determine drusen subtype frequency, and compare subtypes with age-related macular degeneration (AMD) stage and cause of death using an eye-bank model of AMD.

DESIGN

Cross-sectional study.

PARTICIPANTS

Two thousand ninety-two human eyes from 1067 eye-bank donors, selected from a population at risk for AMD.

METHODS

We analyzed donor eye tissue images (2005-2020) using both the 4- and 9-step Minnesota Grading System (MGS), an AMD grading system for eye-bank eyes corresponding to the Age-Related Eye Disease Study classification. The 9-step MGS quantifies total drusen area, hyperpigmentation, and depigmentation. We analyzed reticular pseudodrusen (RPD), basal laminar drusen (BLD), and calcified drusen (CaD) frequency within this population and explored associations with AMD stage, donor age, gender, and cause of death. Statistical analyses were performed using Wilcoxon rank-sum and chi-square tests. Testing encompassed staging eye-bank eyes using MGS analysis.

MAIN OUTCOME MEASURES

Drusen subtype frequency associations with AMD stage and cause of death.

RESULTS

We detected RPD in 228 (13%), BLD in 131 (7%), and CaD in 84 (5%) of the examined eyes (n = 1777). All subtypes were associated with advanced AMD (RPD: odds ratio [OR], 3.4 [95% confidence interval (CI), 2.5-4.5; P < 0.0001]; BLD: OR, 2.2 [95% CI, 1.5-3.2; P < 0.0001]; and CaD: OR, 39.1 [95% CI, 16.8-91.0; P < 0.0001]). Only the RPD subtype was associated statistically with cardiovascular death when compared with those without cardiovascular death (48% vs. 32%; OR, 2.0 [95% CI, 1.4-2.9]; P = 0.0002).

CONCLUSIONS

In a large group of eye-bank eyes selected from a population at risk for AMD and graded using the 4-step and 9-step MGS, RPD, BLD, and especially CaD were associated strongly with advanced AMD. The RPD subtype was associated with a cardiovascular cause of death and may represent an ophthalmologic biomarker for cardiovascular disease.

Drusen and pachydrusen: the definition, pathogenesis, and clinical significance

The pachychoroid disease spectrum encompasses seven major retinal conditions including central serous chorioretinopathy (CSC), polypoidal choroidal vasculopathy (PCV), and pachychoroid neovasculopathy or type I macular neovascularisation (MNV) secondary to chronic persistent thickening and dysfunction of the choroidal vasculature. Drusen are focal yellow-white deposits of extracellular debris, which consist of complement proteins, esterified and nonesterified cholesterol, apolipoproteins, carbohydrates, and trace elements, above the retinal pigment epithelium (RPE) or between the RPE and Bruch's membrane. Although drusen are an essential disease precursor of advanced age-related macular degeneration (AMD), a new entity "pachydrusen" has been identified to be associated with some of the enitites that constitute the pachychoroid spectrum. It remains to be determined what the exact differences are between soft drusen, pseudodrusen, and pachydrusen in terms of phenotype, genotype, and pathogenesis. Improving our knowledge in these areas will inevitably improve our understanding of their clinical significance especially as in disease prediction in AMD and the pachychroid spectrum disorders. It remains controversial whether PCV is a subtype of AMD. Understanding the pathogenesis of different types of drusen may also help in addressing if phenotype and/or genotype of type 1 MNV associated with pachychoroid are similar to type 1 MNV related to AMD. Furthermore, because pachydrusen links two pachychoroid diseases, CSC and PCV, it is also of great interest to investigate if CSC is an early stage or a predictor of PCV in future research. In this review, we share our experience in clinical practice and the latest published evidence-based literature to emphasize the differences and similarities in morphology, pathogenesis, and clinical significance of drusen and pachydrusen, a new member of the pachychoroid spectrum disorders.

AMISH EYE STUDY: Baseline Spectral Domain Optical Coherence Tomography Characteristics of Age-Related Macular Degeneration

PURPOSE

To describe spectral domain optical coherence tomography (SD-OCT) findings in an Amish cohort to assess SD-OCT markers for early age-related macular degeneration (AMD).

METHODS

The authors performed a family-based prospective cohort study of 1,146 elderly Amish subjects (age range 50-99 years) (2,292 eyes) who had a family history of at least 1 individual with AMD. All subjects underwent complete ophthalmic examinations, SD-OCT using both Cirrus and Spectralis (20 × 20° scan area) instruments, fundus autofluorescence, infrared imaging, and color fundus photography. Spectral domain optical coherence tomography characteristics were analyzed in subjects with AMD (with and without subretinal drusenoid deposits [SDDs]) and normal healthy cohorts.

RESULTS

Participants' mean age was 65.2 years (SD ± 11). Color fundus photographic findings in 596 (53%) subjects (1,009 eyes) were consistent with AMD; the remaining 478 (43%) subjects showed no signs of AMD. The choroid was significantly thinner on OCT (242 ± 76 µm, P < 0.001) in those with AMD compared with those without (263 ± 63 µm). Subretinal drusenoid deposits were found in 143 eyes (7%); 11 of the 143 eyes (8%) had no other manifestations of AMD. Drusen volume (P < 0.001) and area of geographic atrophy (P < 0.001) were significantly greater, and choroid was significantly (P < 0.001) thinner in subjects with SDDs versus those without SDDs.

CONCLUSION

The authors describe spectral domain optical coherence tomography characteristics in an elderly Amish population with and without AMD, including the frequency of SDD. Although relatively uncommon in this population, the authors confirmed that SDDs can be found in the absence of other features of AMD and that eyes with SDDs have thinner choroids.

Functionally validated imaging endpoints in the Alabama study on early age-related macular degeneration 2 (ALSTAR2): design and methods

Background

Age-related macular degeneration (AMD), a leading cause of irreversible vision impairment in the United States and globally, is a disease of the photoreceptor support system involving the retinal pigment epithelium (RPE), Bruch’s membrane, and the choriocapillaris in the setting of characteristic extracellular deposits between outer retinal cells and their blood supply. Research has clearly documented the selective vulnerability of rod photoreceptors and rod-mediated (scotopic) vision in early AMD, including delayed rod-mediated dark adaptation (RMDA) and impaired rod-mediated light and pattern sensitivity. The unifying hypothesis of the Alabama Study on Early Macular Degeneration (ALSTAR2) is that early AMD is a disease of micronutrient deficiency and vascular insufficiency, due to detectable structural changes in the retinoid re-supply route from the choriocapillaris to the photoreceptors. Functionally this is manifest as delayed rod-mediated dark adaptation and eventually as rod-mediated visual dysfunction in general.

Methods

A cohort of 480 older adults either in normal macular health or with early AMD will be enrolled and followed for 3 years to examine cross-sectional and longitudinal associations between structural and functional characteristics of AMD. Using spectral domain optical coherence tomography, the association between (1) subretinal drusenoid deposits and drusen, (2) RPE cell bodies, and (3) the choriocapillaris’ vascular density and rod- and cone-mediated vision will be examined. An accurate map and timeline of structure-function relationships in aging and early AMD gained from ALSTAR2, especially the critical transition from aging to disease, will identify major characteristics relevant to future treatments and preventative measures.

Discussion

A major barrier to developing treatments and prevention strategies for early AMD is a limited understanding of the temporal interrelationships among structural and functional characteristics while transitioning from aging to early AMD. ALSTAR2 will enable the development of functionally valid, structural biomarkers for early AMD, suitable for use in forthcoming clinical trials as endpoint/outcome measures. The comprehensive dataset will also allow hypothesis-testing for mechanisms that underlie the transition from aging to AMD, one of which is a newly developed Center-Surround model of cone resilience and rod vulnerability.

Trial registration

ClinicalTrials.gov Identifier NCT04112667, October 7, 2019.

EYES WITH SUBRETINAL DRUSENOID DEPOSITS AND NO DRUSEN: Progression of Macular Findings

PURPOSE

To investigate the macular changes over time in eyes containing subretinal drusenoid deposits (also known as pseudodrusen) with no drusen >63 µm.

METHODS

A consecutive series of patients were examined with color fundus photography, optical coherence tomography, and autofluorescence imaging with fluorescein angiography used as necessary. Exclusionary criteria included macular neovascularization, history of retinal surgery, pseudoxanthoma elasticum, and drusen >63 µm.

RESULTS

There were 85 eyes of 54 patients. The mean age at baseline was 83.6 (±7.8) years, and there were 17 men. The mean follow-up was 5.0 (±2.9) years. At initial optical coherence tomography examination, 12 eyes had extrafoveal atrophy and 17 eyes had vitelliform deposits, which were yellowish white subretinal collections that showed intense hyperautofluorescence. During follow-up, 11 eyes lost vitelliform material. After the disappearance of small deposits, focal hyperpigmentation remained. Loss of larger deposits was associated with noteworthy sequela; six developed subfoveal atrophy and one macular neovascularization close to regressing vitelliform material. Subfoveal geographic atrophy developed in four other eyes without vitelliform material by extension from areas of extrafoveal atrophy. Macular neovascularization developed in seven eyes over follow-up. The CFH Y402H and ARMS2 A69S allele frequencies were 57% and 48.9%, respectively, which is similar to a group of age-related macular degeneration controls. One patient had a novel PRPH2 mutation, but did not have a vitelliform deposit; the remainder had a normal PRPH2 and BEST1 coding sequences.

CONCLUSION

Eyes with subretinal drusenoid deposits and no drusen >63 mm have significant risk for the development of both neovascularization and geographic atrophy, the fundamental components of late age-related macular degeneration. An intermediate step in some eyes was the development of a vitelliform deposit, an entity not traditionally associated with age-related macular degeneration, but in these patients, the material seemed to be an important component of the disease pathophysiology. This vitelliform deposit was not associated with genetic markers for pattern dystrophy or Best disease.

Subretinal Drusenoid Deposits in the Elderly in a Population-Based Study (the Montrachet Study)

Purpose

The aim of this study was to investigate the prevalence of subretinal drusenoid deposits (SDD) and to identify associated factors in an elderly population.

Methods

The participants of the population-based Montrachet study underwent an exhaustive ophthalmologic examination, including color fundus photography and macular spectral domain-optical coherence tomography (SD-OCT), coupled with infrared reflectance imaging. The presence of SDD and other age-related macular degeneration lesions, according to the European Eye Epidemiology SD-OCT classification of macular diseases, and subfoveal choroidal thickness were recorded. Moreover, the association of SDD and both clinical and demographic factors as well as plasma levels of vitamin E and lutein/zeaxanthin (L/Z) were analyzed.

Results

The mean age of patients was 82.3 ± 3.8 years and 62.7% were female. The prevalence of SDD was 18.1% (n = 205) in the subjects with at least one eye interpretable (n = 1135). In multivariate analysis, SDD was positively associated with increasing age (OR, 4.6; 95% CI, 2.8-7.7; P < 0.001 for subjects aged >85 years), female sex (OR, 1.7; 95% CI, 1.2-2.4; P = 0.005), and plasma L/Z level (OR, 1.2; 95% CI, 1.0-1.5; P = 0.039), and negatively associated with lipid-lowering drugs use (OR, 0.5; 95% CI, 0.3-0.9; P = 0.014 for statin medications) and subfoveal choroidal thickness (OR, 0.8; 95% CI, 0.7-0.9; P = 0.002).

Conclusions

The prevalence of SDD was high in subjects older than 75 years, more frequent in women, and was associated with a thinner choroid. The association with lipid-lowering drugs deserves further investigation.

Optical coherence tomography evidence of macular ganglion cell-inner plexiform layer thinning in eyes with subretinal drusenoid deposits

BACKGROUND/OBJECTIVES

The purpose of this study was to evaluate macular ganglion cell layer-inner plexiform layer (GCL-IPL) and choroidal thickness in early age-related macular degeneration (AMD) in eyes with subretinal drusenoid deposits (SDD).

SUBJECTS/METHODS

Comprehensive ophthalmological examination was performed. Near infrared reflectance and raster images using enhanced depth imaging were acquired with spectral domain optical coherence tomography. Drusen and SDD were diagnosed based on raster scans and near infrared reflectance. GCL-IPL maps were generated with automated segmentation and choroidal thickness maps were obtained by manually delineating the choroid-scleral boundary.

RESULTS

Forty-eight eyes from 48 patients (mean age 77.5 ± 5.7, range 68-90 years) with a diagnosis of early AMD and 42 eyes of 42 age-matched control subjects (mean age 76.9 ± 5.7, range 67-88 years) were included. Of these, 28 eyes (58.3%) had drusen alone, 4 eyes (8.3%) had SDD alone, and 16 eyes (33.3%) had drusen associated with SDD. Compared with controls, average choroidal thickness was significantly decreased in AMD eyes (P < 0.05). There was no significant difference in choroidal thickness in eyes with SDD with respect to those with drusen alone. GCL-IPL thickness was reduced in an annular pattern at the 3 and 6 mm macular areas in AMD patients with respect to controls (P < 0.05). GCL-IPL thickness at 3 mm was significantly reduced in eyes with SDD with respect to those with drusen alone (P = 0.03).

CONCLUSIONS

The GCL-IPL is reduced in thickness with an annular pattern in early AMD and is significantly thinner in eyes with SDD.

Antecedents of Soft Drusen, the Specific Deposits of Age-Related Macular Degeneration, in the Biology of Human Macula

AMD pathobiology was irreversibly changed by the recent discovery of extracellular cholesterol-containing deposits in the subretinal space, between the photoreceptors and retinal pigment epithelium (RPE), called subretinal drusenoid deposits (SDDs). SDDs strikingly mirror the topography of rod photoreceptors in human macula, raising the question of whether an equivalent process results in a deposition related to foveal cones. Herein we propose that AMD's pathognomonic lesion-soft drusen and basal linear deposit (BLinD, same material, diffusely distributed)-is the leading candidate. Epidemiologic, clinical, and histologic data suggest that these deposits are most abundant in the central macula, under the fovea. Strong evidence presented in a companion article supports the idea that the dominant ultrastructural component is large apolipoprotein B,E-containing lipoproteins, constitutively secreted by RPE. Lipoprotein fatty acids are dominated by linoleate (implicating diet) rather than docosahexaenoate (implicating photoreceptors); we seek within the retina cellular relationships and dietary drivers to explain soft druse topography. The delivery of xanthophyll pigments to highly evolved and numerous Müller cells in the human fovea, through RPE, is one strong candidate, because Müller cells are the main reservoir of these pigments, which replenish from diet. We propose that the evolution of neuroglial relations and xanthophyll delivery that underlie exquisite human foveal vision came with a price, that is, soft drusen and sequela, long after our reproductive years.

Soft Drusen in Age-Related Macular Degeneration: Biology and Targeting Via the Oil Spill Strategies

AMD is a major cause of legal blindness in older adults approachable through multidisciplinary research involving human tissues and patients. AMD is a vascular-metabolic-inflammatory disease, in which two sets of extracellular deposits, soft drusen/basal linear deposit (BLinD) and subretinal drusenoid deposit (SDD), confer risk for end-stages of atrophy and neovascularization. Understanding how deposits form can lead to insights for new preventions and therapy. The topographic correspondence of BLinD and SDD with cones and rods, respectively, suggest newly realized exchange pathways among outer retinal cells and across Bruch's membrane and the subretinal space, in service of highly evolved, eye-specific physiology. This review focuses on soft drusen/BLinD, summarizing evidence that a major ultrastructural component is large apolipoprotein B,E-containing, cholesterol-rich lipoproteins secreted by the retinal pigment epithelium (RPE) that offload unneeded lipids of dietary and outer segment origin to create an atherosclerosis-like progression in the subRPE-basal lamina space. Clinical observations and an RPE cell culture system combine to suggest that soft drusen/BLinD form when secretions of functional RPE back up in the subRPE-basal lamina space by impaired egress across aged Bruch's membrane-choriocapillary endothelium. The soft drusen lifecycle includes growth, anterior migration of RPE atop drusen, then collapse, and atrophy. Proof-of-concept studies in humans and animal models suggest that targeting the “Oil Spill in Bruch's membrane” offers promise of treating a process in early AMD that underlies progression to both end-stages. A companion article addresses the antecedents of soft drusen within the biology of the macula.

The ARMS2 A69S Polymorphism Is Associated with Delayed Rod-Mediated Dark Adaptation in Eyes at Risk for Incident Age-Related Macular Degeneration

PURPOSE

To examine the association between sequence variants in genetic risk factors for age-related macular degeneration (AMD) and delayed rod-mediated dark adaptation (RMDA), the first functional biomarker for incident AMD, in older adults with normal macular health and early AMD.

DESIGN

Cross-sectional.

PARTICIPANTS

Adults 60 years of age or older showing normal macular health (defined as both eyes at step 1 on the Age-Related Eye Disease Study 9-step AMD classification system) and those with AMD in one or both eyes (defined as steps 2-9).

METHODS

Single nucleotide polymorphisms were genotyped in the complement factor H (CFH) and ARMS2 genes using a Taqman assay. Rod-mediated dark adaptation was assessed in 1 eye after photobleach with targets centered at 5° on the inferior vertical meridian. Rate of dark adaptation was defined by rod intercept time (RIT), duration (in minutes) required for sensitivity to reach a criterion sensitivity level in the latter half of the second component of rod recovery. Associations between CFH and ARMS2 polymorphisms and RMDA were adjusted for age and smoking.

MAIN OUTCOME MEASURE

Rod intercept time.

RESULTS

The sample consisted of 543 participants having both genotype and RIT determination; 408 showed normal macular health and 135 demonstrated AMD, most having early AMD (124 of 135). For the combined sample, higher RIT (slower RMDA) was observed for both the A69S variant in ARMS2 and the Y402H variant in CFH (adjusted P = 0.0001 and P = 0.0023, respectively). For healthy participants, the A69S variant in ARMS2 was associated with higher RIT (adjusted P = 0.0011), whereas the Y402H variant in CFH was not (adjusted P = 0.2175). For AMD patients, the A69S variant of ARMS2 and the Y402H variant of CFH were associated with higher RIT (adjusted P = 0.0182 and P = 0.0222, respectively). Those with a larger number of high-risk ARMS2 and CFH alleles showed higher RIT, in both healthy and AMD groups (adjusted P = 0.0002 and P < 0.0001, respectively).

CONCLUSIONS

We report a novel association wherein older adults with high-risk ARMS2 and CFH genotypes are more likely to demonstrate delayed RMDA, the first functional biomarker for incident early AMD. Before the AMD clinical phenotype is present, those showing normal macular health with the ARMS2 A69S allele demonstrate delayed RMDA. Understanding ARMS2 function is a research priority.

Prevalence of peripapillary choroidal neovascular membranes (PPCNV) in an elderly UK population-the Bridlington eye assessment project (BEAP): a cross-sectional study (2002-2006)

PURPOSE

There is paucity of data on the epidemiology of peripapillary choroidal neovascularisartion (PPCNV). Our aim was to determine prevalence of PPCNV in the elderly UK population of Bridlington residents aged ≥65 years.

METHODS

Eyes with PPCNV in the Bridlington eye assessment project (BEAP) database of 3475 participants were analysed. PPCNV outline was drawn, its area measured, and clock-hour involvement of disc circumference recorded. Location and shortest distance from the lesion edge to fovea were recorded. Masked grading for age-related maculopathy (ARM)/reticular pseudodrusen (RPD) within the ETDRS grid was assigned for each eye using a modified Rotterdam scale. Peripapillary retinal pigment epithelial (RPE) changes/drusen were recorded. Visual acuity (VA) and demographic details analysed separately were merged with grading data.

RESULTS

PPCNV were identified in ten subjects, and were bilateral in two (20%), a population prevalence of 0.29%, and 0.06% bilaterality. Gender-specific prevalence were 0.36% and 0.19% for females and males, respectively. Age ranged from 66 to 85 years [mean 76.3 (SD 6.4)]. PPCNV were located nasal to disc in 41.7%, measuring 0.46-7.93 mm² [mean 2.81 mm² (SD 2.82)]. All PPCNV eyes had peripapillary RPE changes. One subject had no ARM, 1 angioid streaks, and 30% RPD. No direct foveal involvement, or reduced VA attributable to PPCNV was observed.

CONCLUSION

PPCNV were infrequent in this population, more common in females, and often located nasal to the disc, without foveal extension. Peripapillary degenerative changes were universal, and strong association with ARM was observed in eyes with PPCNV. Typically, PPCNV were asymptomatic with VA preservation.

Directional ABCA1-mediated cholesterol efflux and apoB-lipoprotein secretion in the retinal pigment epithelium

Cholesterol-containing soft drusen and subretinal drusenoid deposits (SDDs) occur at the basolateral and apical side of the retinal pigment epithelium (RPE), respectively, in the chorioretina and are independent risk factors for late age-related macular degeneration (AMD). Cholesterol in these deposits could originate from the RPE as nascent HDL or apoB-lipoprotein. We characterized cholesterol efflux and apoB-lipoprotein secretion in RPE cells. Human RPE cells, ARPE-19, formed nascent HDL that was similar in physicochemical properties to nascent HDL formed by other cell types. In highly polarized primary human fetal RPE (phfRPE) monolayers grown in low-lipid conditions, cholesterol efflux to HDL was moderately directional to the apical side and much stronger than ABCA1-mediated efflux to apoA-I at both sides; ABCA1-mediated efflux was weak and equivalent between the two sides. Feeding phfRPE monolayers with oxidized or acetylated LDL increased intracellular levels of free and esterified cholesterol and substantially raised ABCA1-mediated cholesterol efflux at the apical side. phfRPE monolayers secreted apoB-lipoprotein preferentially to the apical side in low-lipid and oxidized LDL-feeding conditions. These findings together with evidence from human genetics and AMD pathology suggest that RPE-generated HDL may contribute lipid to SDDs.

IMPROVING THE AGE-RELATED MACULAR DEGENERATION CONSTRUCT: A New Classification System

Previous models of disease in age-related macular degeneration (AMD) were incomplete in that they did not encompass subretinal drusenoid deposits (pseudodrusen), subtypes of neovascularization, and polypoidal choroidal vasculopathy. In addition, Type 3 neovascularization starts in the retina and may not necessarily involve the choroid. As such, the term choroidal neovascularization is not appropriate for these eyes. The new aspects in the AMD construct are to include specific lipoprotein extracellular accumulations, namely drusen and subretinal drusenoid deposits, as early AMD. The deposition of specific types of deposit seems to be highly correlated with choroidal thickness and topographical location in the macula. Late AMD includes macular neovascularization or atrophy. The particular type of extracellular deposit is predictive of the future course of the patient. For example, eyes with subretinal drusenoid deposits have a propensity to develop outer retinal atrophy, complete outer retinal and retinal pigment epithelial atrophy, or Type 3 neovascularization as specific forms of late AMD. Given Type 3 neovascularization may never involve the choroid, the term macular neovascularization is suggested for the entire spectrum of neovascular disease in AMD. In contrast to older classification systems, the proposed system encompasses the relevant presentations of disease and more precisely predicts the future course of the patient. In doing so, the concept was developed that there may be genetic risk alleles, which are not necessarily the same alleles that influence disease expression.

Subretinal drusenoid deposits AKA pseudodrusen

A distinction between conventional drusen and pseudodrusen was first made in 1990, and more recently knowledge of pseudodrusen, more accurately called subretinal drusenoid deposits (SDDs), has expanded. Pseudodrusen have a bluish-white appearance by biomicroscopy and color fundus photography. Using optical coherence tomography, pseudodrusen were found to be accumulations of material internal to the retinal pigment epithelium that could extend internally through the ellipsoid zone. These deposits are more commonly seen in older eyes with thinner choroids. Histologic evaluation of these deposits revealed aggregations of material in the subretinal space between photoreceptors and retinal pigment epithelium. SDDs contain some proteins in common with soft drusen but differ in lipid composition. Many studies reported that SDDs are strong independent risk factors for late age-related macular degeneration. Geographic atrophy and type 3 neovascularization are particularly associated with SDD. Unlike conventional drusen, eyes with SDD show slow dark adaptation and poor contrast sensitivity. Outer retinal atrophy develops in eyes with regression of SDD, a newly recognized form of late age-related macular degeneration. Advances in imaging technology have enabled many insights into this condition, including associated photoreceptor, retinal pigment epithelium, and underlying choroidal changes.

KUS121, an ATP regulator, mitigates chorioretinal pathologies in animal models of age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness among elderly people. The appearance of drusen is a clinical manifestation and a harbinger of both exudative and atrophic AMD. Recently, antibody-based medicines have been used to treat the exudative type. However, they do not restore good vision in patients. Moreover, no effective treatment is available for atrophic AMD. We have created small chemicals (Kyoto University Substances; KUSs) that act as ATP regulators inside cells. In the present study, we examined the in vivo efficacy of KUS121 in C-C chemokine receptor type 2-deficient mice, a mouse model of AMD. Systemic administration of KUS121 prevented or reduced drusen-like lesions and endoplasmic reticulum stress, and then substantially mitigated chorioretinal pathologies with significant preservation of visual function. Additionally, we confirmed that long-term oral administration of KUS121 caused no systemic complications in drusen-affected monkeys. ATP regulation by KUSs may represent a novel strategy in the treatment of drusen and prevention of disease progression in AMD.

Relationship between reticular pseudodrusen and choroidal thickness in intermediate age-related macular degeneration

IMPORTANCE

Reticular pseudodrusen (RPD) is strongly associated with late age-related macular degeneration (AMD) but their aetiology remains unknown. RPD have been associated with reduced choroidal thickness (ChT) but most studies are limited by small sample size and varying severity of AMD.

BACKGROUND

To investigate the relationship between choroidal thickness and RPD in eyes with intermediate AMD (iAMD), controlling for variables known to influence ChT.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Participants were recruited from Centre for Eye Research Australia.

METHODS

Colour fundus photographs, fundus auto fluorescence, near-infrared and spectral-domain ocular coherence tomography (OCT) were graded for RPD. ChT was measured from enhanced-depth imaging OCT scans at the centre of fovea, 1500 and 3000 μm nasal, temporal, superior and inferior from centre of fovea.

MAIN OUTCOME MEASURES

ChT between RPD and non-RPD group.

RESULTS

A total of 297 eyes from 152 subjects were included. A total of 84 (28%) had RPD and were older than non-RPD group (75.1 ± 5.4 years and 68.7 ± 6.9 years, respectively; P < 0.001). In unadjusted analysis, the RPD group was significantly associated with thinner choroids across all measured locations (P ≤ 0.022). After adjustment for variables, the presence of RPD was no longer associated with ChT (P ≥ 0.132 for all locations) but age (P < 0.001) and refractive error (P = 0.002) remained significantly associated with ChT.

CONCLUSIONS AND RELEVANCE

Age and refractive error, rather than RPD, was significantly associated with reduced ChT in eyes with iAMD. Choroidal insufficiency may be a less important variable in RPD aetiology than previously considered.

ASSOCIATION BETWEEN VISUAL FUNCTION AND SUBRETINAL DRUSENOID DEPOSITS IN NORMAL AND EARLY AGE-RELATED MACULAR DEGENERATION EYES

PURPOSE

To examine the association between subretinal drusenoid deposits (SDDs) identified by multimodal retinal imaging and visual function in older eyes with normal macular health or in the earliest phases of age-related macular degeneration (AMD).

METHODS

Age-related macular degeneration status for each eye was defined according to the Age-Related Eye Disease Study (AREDS) 9-step classification system (normal = Step 1, early AMD = Steps 2-4) based on color fundus photographs. Visual functions measured were best-corrected photopic visual acuity, contrast and light sensitivity, mesopic visual acuity, low-luminance deficit, and rod-mediated dark adaptation. Subretinal drusenoid deposits were identified through multimodal imaging (color fundus photographs, infrared reflectance and fundus autofluorescence images, and spectral domain optical coherence tomography).

RESULTS

The sample included 1,202 eyes (958 eyes with normal health and 244 eyes with early AMD). In normal eyes, SDDs were not associated with any visual function evaluated. In eyes with early AMD, dark adaptation was markedly delayed in eyes with SDDs versus no SDD (a 4-minute delay on average), P = 0.0213. However, this association diminished after age adjustment, P = 0.2645. Other visual functions in early AMD eyes were not associated with SDDs.

CONCLUSION

In a study specifically focused on eyes in normal macular health and in the earliest phases of AMD, early AMD eyes with SDDs have slower dark adaptation, largely attributable to the older ages of eyes with SDD; they did not exhibit deficits in other visual functions. Subretinal drusenoid deposits in older eyes in normal macular health are not associated with any visual functions evaluated.

Macular Atrophy Development and Subretinal Drusenoid Deposits in Anti-Vascular Endothelial Growth Factor Treated Age-Related Macular Degeneration

Purpose

To explore the association between presence of subretinal drusenoid deposits (SDD) at baseline in eyes with neovascular age-related macular degeneration (nAMD) with the development of macular atrophy (MA) during anti-vascular endothelial growth factor (VEGF) therapy.

Methods

There were 74 eyes without pre-existing MA receiving anti-VEGF therapy for nAMD for 2 years or longer analyzed. At least two image modalities that included spectral-domain optical coherence tomography, near-infrared reflectance, fluorescein angiography, and color fundus photos were used to assess for SDD presence, phenotype (dot and ribbon), and location, neovascularization type, and MA. Logistic regression models using generalized estimating equations assessed the association between SDD and the development of MA adjusting for age, neovascularization type, and choroidal thickness.

Results

SDD were present in 46 eyes (63%) at baseline. MA developed in 38 eyes (51%) during the mean of 4.7 ± 1.2 years of follow-up. Compared with eyes without SDD, those with SDD at baseline were 3.0 times (95% confidence interval [CI] 1.1–8.5, P = 0.0343) more likely to develop MA. Eyes with SDD present in the inferior macula and inferior extramacular fields at baseline were 3.0 times and 6.5 times more likely to develop MA at follow-up than eyes without SDD in these locations (95% CI 1.0–8.9, P = 0.0461 and 95% CI 1.3–32.4, P = 0.0218, respectively). MA development was not associated with a specific SDD phenotype.

Conclusions

MA frequently developed in eyes during anti-VEGF treatment. SDD were independently associated with MA development. The extension of SDD into the inferior fundus, particularly in the inferior extramacular field, conferred higher odds of subsequent MA development.

The Progression of Geographic Atrophy Secondary to Age-Related Macular Degeneration

Geographic atrophy (GA) is an advanced form of age-related macular degeneration (AMD) that leads to progressive and irreversible loss of visual function. Geographic atrophy is defined by the presence of sharply demarcated atrophic lesions of the outer retina, resulting from loss of photoreceptors, retinal pigment epithelium (RPE), and underlying choriocapillaris. These lesions typically appear first in the perifoveal macula, initially sparing the foveal center, and over time often expand and coalesce to include the fovea. Although the kinetics of GA progression are highly variable among individual patients, a growing body of evidence suggests that specific characteristics may be important in predicting disease progression and outcomes. This review synthesizes current understanding of GA progression in AMD and the factors known or postulated to be relevant to GA lesion enlargement, including both affected and fellow eye characteristics. In addition, the roles of genetic, environmental, and demographic factors in GA lesion enlargement are discussed. Overall, GA progression rates reported in the literature for total study populations range from 0.53 to 2.6 mm²/year (median, ∼1.78 mm²/year), assessed primarily by color fundus photography or fundus autofluorescence (FAF) imaging. Several factors that could inform an individual's disease prognosis have been replicated in multiple cohorts: baseline lesion size, lesion location, multifocality, FAF patterns, and fellow eye status. Because best-corrected visual acuity does not correspond directly to GA lesion enlargement due to possible foveal sparing, alternative assessments are being explored to capture the relationship between anatomic progression and visual function decline, including microperimetry, low-luminance visual acuity, reading speed assessments, and patient-reported outcomes. Understanding GA progression and its individual variability is critical in the design of clinical studies, in the interpretation and application of clinical trial results, and for counseling patients on how disease progression may affect their individual prognosis.

Cuticular Drusen: Clinical Phenotypes and Natural History Defined Using Multimodal Imaging

PURPOSE

To define the range and life cycles of cuticular drusen phenotypes using multimodal imaging and to review the histologic characteristics of cuticular drusen.

DESIGN

Retrospective, observational cohort study and experimental laboratory study.

PARTICIPANTS

Two hundred forty eyes of 120 clinic patients with a cuticular drusen phenotype and 4 human donor eyes with cuticular drusen (n = 2), soft drusen (n = 1), and hard drusen (n = 1).

METHODS

We performed a retrospective review of clinical and multimodal imaging data of patients with a cuticular drusen phenotype. Patients had undergone imaging with various combinations of color photography, fluorescein angiography, indocyanine green angiography, near-infrared reflectance, fundus autofluorescence, high-resolution OCT, and ultrawide-field imaging. Human donor eyes underwent processing for high-resolution light and electron microscopy.

MAIN OUTCOME MEASURES

Appearance of cuticular drusen in multimodal imaging and the topography of a cuticular drusen distribution; age-dependent variations in cuticular drusen phenotypes, including the occurrence of retinal pigment epithelium (RPE) abnormalities, choroidal neovascularization, acquired vitelliform lesions (AVLs), and geographic atrophy (GA); and ultrastructural and staining characteristics of druse subtypes.

RESULTS

The mean age of patients at the first visit was 57.9±13.4 years. Drusen and RPE changes were seen in the peripheral retina, anterior to the vortex veins, in 21.8% of eyes. Of eyes with more than 5 years of follow-up, cuticular drusen disappeared from view in 58.3% of eyes, drusen coalescence was seen in 70.8% of eyes, and new RPE pigmentary changes developed in 56.2% of eyes. Retinal pigment epithelium abnormalities, AVLs, neovascularization, and GA occurred at a frequency of 47.5%, 24.2%, 12.5%, and 25%, respectively, and were significantly more common in patients older than 60 years of age (all P < 0.015). Occurrence of GA and neovascularization were important determinants of final visual acuity in eyes with the cuticular drusen phenotype (both P < 0.015). Small cuticular drusen typically demonstrated a homogenous ultrastructural appearance similar to hard drusen, whereas fragmentation of the central and basal contents was seen frequently in larger cuticular drusen.

CONCLUSIONS

Although the ultrastructural characteristics of cuticular drusen appear more similar to those of hard drusen, their lifecycle and macular complications are more comparable with those of soft drusen. Cuticular drusen phenotype may confer a unique risk for the development of GA and neovascularization.

Regulated efflux of photoreceptor outer segment-derived cholesterol by human RPE cells

Genetic studies have linked age-related macular degeneration (AMD) to genes involved in high-density lipoprotein (HDL) metabolism, including ATP-binding cassette transporter A1 (ABCA1). The retinal pigment epithelium (RPE) handles large amounts of lipids, among others cholesterol, partially derived from internalized photoreceptor outer segments (OS) and lipids physiologically accumulate in the aging eye. To analyze the potential function of ABCA1 in the eye, we measured cholesterol efflux, the first step of HDL generation, in RPE cells. We show the expression of selected genes related to HDL metabolism in mouse and human eyecups as well as in ARPE-19 and human primary RPE cells. Immunofluorescence staining revealed localization of ABCA1 on both sides of polarized RPE cells. This was functionally confirmed by directional efflux to apolipoprotein AI (ApoA-I) of ³H-labeled cholesterol given to the cells via serum or via OS. ABCA1 expression and activity was modulated using a liver-X-receptor (LXR) agonist and an ABCA1 neutralizing antibody, demonstrating that the efflux was ABCA1-dependent. We concluded that the ABCA1-mediated lipid efflux pathway, and hence HDL biosynthesis, is functional in RPE cells towards both the basal (choroidal) and apical (subretinal) space. Impaired activity of the pathway might cause age-related perturbations of lipid homeostasis in the outer retina and thus may contribute to disease development and/or progression.

Spotlight on reticular pseudodrusen

Age-related macular degeneration (AMD) is a leading cause of vision loss in patients >50 years old. The hallmark of the disease is represented by the accumulation of extracellular material between retinal pigment epithelium and the inner collagenous layer of Bruch's membrane, called drusen. Although identified almost 30 years ago, reticular pseudodrusen (RPD) have been recently recognized as a distinctive phenotype. Unlike drusen, they are located in the subretinal space. RPD are strongly associated with late AMD, especially geographic atrophy, type 2 and 3 choroidal neovascularization, which, in turn, are less common in typical AMD. RPD identification is not straightforward at fundus examination, and their identification should employ at least 2 different imaging modalities. In this narrative review, we embrace all aspects of RPD, including history, epidemiology, histology, imaging, functional test, natural history and therapy.