Nonexudative Macular Neovascularization Supporting Outer Retina in Age-Related Macular Degeneration: A Clinicopathologic Correlation

Anti-VEGF Treatment for Secondary Neovascularization in Pseudoxanthoma Elasticum - Age of Onset, Treatment Frequency, and Visual Outcome

PURPOSE

To assess the onset, treatment frequency, and visual outcome of anti-vascular endothelial growth factor (anti-VEGF) treatment due to secondary choroidal neovascularization (CNV) in patients with pseudoxanthoma elasticum (PXE).

DESIGN

Retrospective cohort study METHODS: One-hundred six eyes of 53 patients with PXE were analyzed. The assessment of CNV activity relied on hemorrhage visible on funduscopy and intra- / subretinal fluid on optical coherence tomography (OCT), individually defining a shortening or extension of treatment interval. Best-corrected visual acuity (BCVA) at baseline, age at anti-VEGF therapy initiation, and BCVA-drop events at exudation onset (worsening of BCVA of 2 or more lines) were documented. Further, we assessed the number of injections during the first year and the total number of injections, the time to treatment initiation of the fellow eye, and BCVA over time.

RESULTS

During a median observation period of 77 months (IQR 49; 126) patients received a median number of 28.0 anti-VEGF-injections (IQR 9.8; 43.5). Eight patients received no injection (median age at baseline 38.1 years), 11 patients underwent anti-VEGF treatment in one eye (median age 47.2 years) and 34 patients in both eyes (median age 51.8 years). The median age at the first anti-VEGF treatment was 52.80 years (IQR 47.2-57.6). Applying Cox regression models, the median "survival" time of fellow eye until treatment initiation was 16.8 months. In the group of bilateral treated patients, the median time difference was 9.6 months (IQR 2.1- 32.4, range 0-122) The median number of injections was 5.5 per eye in the first year of treatment (IQR 3-7) and was associated with the total number of injections in the observation period (2.33, CI 1.22-3.44, P < .001). A better BCVA at the last follow-up visit was associated with a better baseline BCVA (P < .001, R2 = 0.318) and with the absence of a BCVA drop at the onset of exudation (P = 0.035, R2 = 0.339).

CONCLUSIONS

The results of this study indicate that anti-VEGF treatment is required for most PXE patients at a relatively young age. Once treatment in one eye is initiated, the time to fellow eye treatment is relatively short. A BCVA drop before treatment initiation is a risk factor for worse visual outcomes, suggesting that treatment is prudent before exudation affects the central retina. Given the young age of onset and intensive treatment needs, patients with PXE might particularly benefit from longer-acting anti-VEGF therapeutics.

Predict and Protect: Evaluating the Double-Layer Sign in Age-Related Macular Degeneration

INTRODUCTION

Advanced age-related macular degeneration (AMD) is a major cause of vision loss. Therefore, there is interest in precursor lesions that may predict or prevent the onset of advanced AMD. One such lesion is a shallow separation of the retinal pigment epithelium (RPE) and Bruch's membrane (BM), which is described by various terms, including double-layer sign (DLS).

METHODS

In this article, we aim to examine and clarify the different terms referring to shallow separation of the RPE and BM. We also review current evidence on the outcomes associated with DLS: firstly, whether DLS is predictive of exudative neovascular AMD; and secondly, whether DLS has potential protective properties against geographic atrophy.

RESULTS

The range of terms used to describe a shallow separation of the RPE and BM reflects that DLS can present with different characteristics. While vascularised DLS appears to protect against atrophy but can progress to exudation, non-vascularised DLS is associated with an increased risk of atrophy. Optical coherence tomography (OCT) angiography (OCTA) is the principal method for identifying and differentiating various forms of DLS. If OCTA is unavailable or not practically possible, simplified classification of DLS as thick or thin, using OCT, enables the likelihood of vascularisation to be approximated. Research is ongoing to automate DLS detection by applying deep-learning algorithms to OCT scans.

CONCLUSIONS

The term DLS remains applicable for describing shallow separation of the RPE and BM. Detection and classification of this feature provides valuable information regarding the risk of progression to advanced AMD. However, the appearance of DLS and its value in predicting AMD progression can vary between patients. With further research, individualised risks can be confirmed to inform appropriate treatment.

Prevalence, Features, and Outcomes of Type 1 Neovascularization in Eyes with Angioid Streaks

PURPOSE

This study aimed to delineate the characteristics, prevalence, and outcomes of neovascularization (NV), particularly aneurysmal Type 1 NV, in patients with angioid streaks (AS) secondary to pseudoxanthoma elasticum (PXE), and to introduce a clinical classification based on multimodal imaging (MMI).

DESIGN

Retrospective longitudinal cohort study.

PARTICIPANTS

85 patients (168 eyes) with AS secondary to PXE at two tertiary referral centers.

METHODS

Data collection included demographic, medical, and ocular histories. Diagnostic methods comprised fundus photography, autofluorescence, indocyanine green angiography, optical coherence tomography (OCT), and OCT angiography.

MAIN OUTCOME MEASURES

Prevalence of Type 1 NV, visual acuity (VA), risk of exudation.

RESULTS

Type 1 NV was identified in 127 eyes (76%), with 85 of these (67%) showing exclusively Type 1 NV. These lesions often originated around the disc, at sites of Bruch's membrane dehiscences, and followed the path of AS, extending to the posterior pole in 101 eyes (80%). Despite 65% of Type 1 NV remaining non-exudative, 36% evolved into exudative over five years, and 11 eyes experienced mid-peripheral subretinal hemorrhages. Aneurysmal dilations, observed in 57% of cases, substantially increased exudation risk (hazard ratio = 3.86, p=0.02). Despite treatment, VA significantly deteriorated in exudative Type 1 NV (p=0.02). Type 2 NV, detected in 56 eyes (33%), often coexisted with Type 1 NV and was associated with poorer visual outcomes and higher rates of macular atrophy. A classification of AS was developed, ranging from empty AS (stage 0, no NV) to advanced NV (stage 3, both Type 1 and Type 2 NV).

CONCLUSIONS

Type 1 NV predominates in AS. Although predominantly non-exudative, its progression correlates with substantial visual impairment, similar to the deficits observed with Type 2 NV. Aneurysmal Type 1 NV poses a significant exudation risk, underscoring the need for vigilant monitoring.

Topographic Measurement of the Subretinal Pigment Epithelium Space in Normal Aging and Age-Related Macular Degeneration Using High-Resolution OCT

Purpose

A micrometer scale hyporeflective band within the retinal pigment epithelium basal lamina - Bruch's membrane complex (RPE-BL-BrM) was topographically measured in aging and age-related macular degeneration (AMD).

Methods

In a prospective cross-sectional study, 90 normal eyes from 76 subjects (range = 23-90 years) and 53 dry AMD eyes from 47 subjects (range = 62-91 years) were enrolled. Isotropic volume raster scans over 6 mm × 6 mm (500 × 500 A-scans) were acquired using a high-resolution (2.7 µm axial resolution) spectral-domain optical coherence tomography (SD-OCT) prototype instrument. Six consecutive optical coherence tomography (OCT) volumes were computationally motion-corrected and fused to improve feature visibility. A boundary regression neural network was developed to measure hyporeflective band thickness. Topographic dependence was evaluated over a 6-mm-diameter Early Treatment Diabetic Retinopathy Study (ETDRS) grid.

Results

The hyporeflective band thickness map (median of 4.3 µm and 7.8 µm in normal and AMD eyes, respectively) is thicker below and radially symmetric around the fovea. In normal eyes, age-associated differences occur within 0.7 to 2.3 mm from the foveal center (P < 0.05). In AMD eyes, the hyporeflective band is hypothesized to be basal laminar deposits (BLamDs) and is thicker within the 3-mm ETDRS circle (P < 0.0002) compared with normal eyes. The inner ring is the most sensitive location to detect age versus AMD-associated changes within the RPE-BL-BrM. AMD eyes with subretinal drusenoid deposits (SDDs) have a significantly thicker hyporeflective band (P < 0.001) than those without SDDs.

Conclusions

The hyporeflective band is a quantifiable biomarker which differentiates AMD from aging. Longitudinal studies are warranted. The hyporeflective band may be a useful biomarker for risk stratification and disease progression.

Effect of baseline fluid localization on visual acuity and prognosis in type 1 macular neovascularization treated with anti-VEGF

PURPOSE

To assess the prognostic value of subretinal (SRF) and intraretinal fluid (IRF) localizations in type 1 macular neovascularization (MNV) due to age-related macular degeneration (AMD).

SUBJECTS

Eyes were prospectively treated with anti-vascular epithelial growth factor (anti-VEGF) intravitreal injections (IVT) according to a Pro-Re-Nata (PRN) or Treat and Extend (TAE) regimen during 24 months. A total of 211 eyes with treatment-naïve type 1 MNV secondary to AMD were consecutively included. Eyes were divided between 2 groups according to the fluid localization: presence of SRF alone (SRF group), or presence of IRF associated or not with SRF (IRF ± SRF group).

RESULTS

At baseline the mean BCVA was 66.2 letters. SRF was present in 94.8% of eyes, IRF in 30.8%, and both in 25.6%. Data were available for 201 eyes at 12 months, and 157 eyes at 24 months. The presence of IRF at baseline was associated with lower baseline BCVA and significantly lower BCVA at 12 months (p < 0.001) and 24 months (p < 0.001). Eyes with SRF alone displayed better visual outcomes (BCVA at month 12, SRF = 74.3 letters, IRF ± SRF = 56.9 letters). In the presence of baseline IRF, fibrosis (p = 0.03) and atrophy (p < 0.001) were more frequently found at 24 months. In a multivariate model, the presence of baseline IRF was significantly associated with lower BCVA at month 12 but not at month 24.

CONCLUSION

In type 1 MNV, the presence of baseline IRF was associated with worse visual outcomes compared to SRF alone, and more frequent atrophy and fibrosis.

The "triple-layer sign": an optical coherence tomography signature for the detection of non-exudative macular neovascularization

PURPOSE

To assess the sensitivity and specificity of the "triple layer sign" (TLS) (retinal pigment epithelium (RPE), neovascular tissue, and Bruch's membrane) on structural optical coherence tomography (OCT) images for the diagnosis of treatment-naïve non-exudative type-1 macular neovascularization (NE-MNV) in age-related macular degeneration (AMD).

DESIGN

Cross-sectional study.

METHODS

Two masked retinal experts evaluated the presence of the TLS in eyes with NE-MNV and controls with an RPE elevation without exudation due to other causes than NE-MNV in AMD [e.g., medium-large drusen, cuticular drusen, basal laminar deposits (BlamD)].

RESULTS

130 eyes of 98 consecutive patients met the study criteria; 40 eyes of 40 patients satisfied the criteria for being included in the NE-MNV secondary to AMD group (27 females, 13 males, with a mean age of 73.8 ± 8.0 years), and 90 eyes of 58 patients met the criteria to be included in the control group (31 eyes were included in the medium-to-large drusen sub-group, 32 eyes in the cuticular drusen sub-group, and 27 eyes in the BlamD group. The TLS was observed in 39/40 patients with NE-MNV and 8/90 controls. The sensitivity and specificity of the TLS for the diagnosis of NE-MNV were 97% and 91%, respectively.

CONCLUSIONS

The TLS on OCT demonstrated high sensitivity and specificity values in detecting treatment-naive type 1 NE-MNV.

Analysis of Choriocapillaris Reperfusion Topography Following Faricimab Treatment for Neovascular Age-Related Macular Degeneration in Therapy-Naïve Patients

INTRODUCTION

To assess changes in choriocapillaris (CC) vascular density surrounding macular neovascularization (MNV) in treatment-naïve age-related macular degeneration (AMD) after faricimab application using optical coherence tomography angiography (OCTA).

METHODS

Twenty-five eyes of 25 treatment-naïve individuals who underwent intravitreal faricimab injections for neovascular AMD (nAMD) with type 1 MNV were included. Spectral-domain optical coherence tomography (SD-OCT) images and en-face swept-source OCTA images were analyzed, and the percentage of CC flow deficit (FD%), FD average area (FDa) and FD number (FDn) in five progressive 20.0-μm-wide concentric rings (R1, R2, R3, R4 and R5) surrounding the dark halo around the MNV were calculated. Image acquisition was carried out prior to the first faricimab injection (T0) and 1 month after the injection (T1).

RESULTS

The topographical sub-analysis revealed noteworthy changes in all rings at T1 compared to T0. There was a notable progressive reduction in FD% at T1 compared to T0 values across all rings, indicating a gradual CC reperfusion following anti-VEGF treatment. Additionally, the average size of FD decreased after the loading phase. Although not reaching statistical significance, there was a progressive reduction in the FDa across all rings.

CONCLUSION

Our study highlights a CC FD reduction following the administration of three consecutive faricimab injections. This effect was detected in all rings surrounding the dark halo. These observations suggest a partial CC reperfusion surrounding the MNV, potentially serving as an indicator for disease regression.

Factors associated with the development of exudation in treatment-naive eyes with nonexudative macular neovascularization

PURPOSE

To identify the predictive factors for development of exudation in patients with treatment-naïve nonexudative macular neovascularization (MNV).

METHODS

We retrospectively analyzed 61 treatment-naïve patients with nonexudative MNV who had not received treatment for nonexudative MNV before the exudation developed. Baseline characteristics and changes in MNV were evaluated using multivariate modeling to determine the potential risk factors for exudative conversion.

RESULTS

Exudation development was identified in 31.1% (19/61 eyes) of the study eyes during the 46.2 ± 8.2-month mean follow-up period. The mean period of development of exudation from the baseline was 21.5 ± 6.7 months. Multivariate Cox regression analysis identified that older age (hazard ratio [HR] of 1.380, 95% confidence interval [CI] 1.129-1.688, P = 0.008), larger MNV area at baseline (HR of 1.715, CI 1.288-2.308; P = 0.006), increase of MNV area by doubling (HR of 4.992, CI 1.932-9.246; P = 0.002), and retinal pigment epithelium (RPE) elevation more than 100 μm (HR of 1.017, CI 1.006-1.233; P = 0.015) were associated with increased risk of the development of exudation.

CONCLUSION

Older age, larger MNV area, increasing MNV area, and higher RPE elevation were associated with an increased risk of exudative conversion in patients with treatment-naïve nonexudative MNV. Identifying these risk factors may be helpful in establishing treatment strategies and monitoring patients.

PHENOTYPIC CHARACTERIZATION OF PREDICTORS FOR DEVELOPMENT AND PROGRESSION OF GEOGRAPHIC ATROPHY USING OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To evaluate the impact of optical coherence tomography phenotypes preceding atrophy related to age-related macular degeneration on the progression of atrophic lesions.

METHODS

In this observational retrospective cohort study, a total of 70 eyes of 60 consecutive patients with intermediate age-related macular degeneration with a minimum follow-up of 24 months were included. The atrophy was quantified using fundus autofluorescence, also considering the directionality of atrophy as centrifugal and centripetal progression rates. The main outcome measures were geographic atrophy (GA) progression rate (mm 2 /year) and square root transformation of GA (mm 2 /year).

RESULTS

The best-fit model for GA (odds ratio: 1.81, P < 0.001) and square root transformation of GA (odds ratio: 1.36, P < 0.001) areas revealed that the main baseline predictor was the presence of a retinal pigment epithelium-basal lamina-Bruch membrane splitting. Large drusen at baseline appeared protective for the GA area lesion expansion over time (odds ratio: 0.52, P < 0.001) when considered with other confounders.

CONCLUSION

A thin retinal pigment epithelium-basal lamina-Bruch membrane splitting without evidence of neovascularization on optical coherence tomography angiography likely represents an optical coherence tomography signature for late basal laminar deposits. Identifying this phenotype can help identify individuals with a higher risk of rapid progression and atrophy expansion.

Age-Related Macular Degeneration, a Mathematically Tractable Disease

A progression sequence for age-related macular degeneration onset may be determinable with consensus neuroanatomical nomenclature augmented by drusen biology and eye-tracked clinical imaging. This narrative review proposes to supplement the Early Treatment of Diabetic Retinopathy Study (sETDRS) grid with a ring to capture high rod densities. Published photoreceptor and retinal pigment epithelium (RPE) densities in flat mounted aged-normal donor eyes were recomputed for sETDRS rings including near-periphery rich in rods and cumulatively for circular fovea-centered regions. Literature was reviewed for tissue-level studies of aging outer retina, population-level epidemiology studies regionally assessing risk, vision studies regionally assessing rod-mediated dark adaptation (RMDA), and impact of atrophy on photopic visual acuity. The 3 mm-diameter xanthophyll-rich macula lutea is rod-dominant and loses rods in aging whereas cone and RPE numbers are relatively stable. Across layers, the largest aging effects are accumulation of lipids prominent in drusen, loss of choriocapillary coverage of Bruch's membrane, and loss of rods. Epidemiology shows maximal risk for drusen-related progression in the central subfield with only one third of this risk level in the inner ring. RMDA studies report greatest slowing at the perimeter of this high-risk area. Vision declines precipitously when the cone-rich central subfield is invaded by geographic atrophy. Lifelong sustenance of foveal cone vision within the macula lutea leads to vulnerability in late adulthood that especially impacts rods at its perimeter. Adherence to an sETDRS grid and outer retinal cell populations within it will help dissect mechanisms, prioritize research, and assist in selecting patients for emerging treatments.

The Double Layer Sign Is Highly Predictive of Progression to Exudation in Age-Related Macular Degeneration

PURPOSE

The presences of a double layer sign (DLS) and a shallow irregular retinal pigment epithelium (RPE) elevation (SIRE) were investigated using spectral domain-OCT (SD-OCT) imaging to determine their ability to predict progression to exudative macular neovascularization (eMNV) in the unaffected fellow eyes (study eye) of participants with age-related macular degeneration (AMD) with newly diagnosed unilateral eMNV.

DESIGN

Retrospective, reanalysis of SD-OCT scans of study eyes from the Early Detection of Neovascular AMD (EDNA) study with 3 years follow-up (FU).

PARTICIPANTS

The EDNA study repository of SD-OCT scans was assessed for inclusion. Cases with incomplete data sets, low quality scans, or exhibiting other pathology were excluded, which resulted in 459 eligible cases.

METHODS

Spectral domain-OCT volume scans of study eyes were graded for irregular elevation of the RPE (IE), with length, and height measurements made on the most affected B-scan. Eyes with heterogeneous reflectivity within the IE were classified as exhibiting the DLS. Eyes with DLS where the length of separation between RPE and Bruch's membrane was ≥ 1000 μm in length and < 100 μm in height were subclassified as SIRE.

MAIN OUTCOME MEASURES

Hazard of progression to eMNV for DLS and SIRE.

RESULTS

Of the 459 eyes, 268 had IE, of which 101 were DLS-like and 51 also fulfilled criteria for SIRE. Over the 3 years FU period, 104 (23%) eyes progressed to eMNV. After an FU of 18 months, a significantly higher proportion of study eyes (P < 0.001) with IE, DLS, and SIRE developed eMNV compared with those without these features (IE: 17% vs. no IE 6.3%; DLS: 23% vs. no DLS 9.9%; SIRE: 22% vs. no SIRE 11%). In the adjusted Cox regression models, a significantly greater hazard of progression (P < 0.001) was associated with the presence of IE (adjusted hazard ratio [HR], 3.01; 95% confidence interval [CI], 1.88-4.82), DLS (adjusted HR, 3.41; 95% CI, 2.26-5.14), or SIRE (adjusted HR, 2.83; 95% CI, 1.68-4.75).

CONCLUSION

The DLS is a highly sensitive predictor of progression to eMNV, and the use of SIRE does not improve predictability.

FINANCIAL DISCLOSURE(S)

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

Reduction of retinal vessel density in non-exudative macular neovascularization: a retrospective study

Purpose

The purpose of this study is to identify predictive activation biomarkers in retinal microvascular characteristics of non-exudative macular neovascularization (MNV) and avoid delayed treatment or overtreatment of subclinical MNV. The main objective is to contribute to the international debate on a new understanding of the role of retinal vessel features in the pathogenesis and progression of non-exudative MNV and age-related macular degeneration (AMD). A discussion on revising-related clinical protocols is presented.

Methods

In this retrospective study, the authors included eyes with non-exudative MNV, eyes with exudative AMD, and normal eyes of age-matched healthy subjects. The parameters were obtained by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA).

Results

In total, 21 eyes with exudative AMD, 21 eyes with non-exudative MNV, and 20 eyes of 20 age-matched healthy subjects without retinal pathology were included. Vessel density (VD) of the deep vascular complex (DVC) in eyes with non-exudative MNV was significantly greater than that in eyes with exudative AMD (p = 0.002), while for superficial vascular plexus (SVP) metrics, no VD differences among sectors were observed between eyes with non-exudative MNV and eyes with exudative AMD.

Conclusion

The reduction in retinal vessel density, especially in the DVC, seems to be involved in or be accompanied by non-exudative MNV activation and should be closely monitored during follow-up visits in order to ensure prompt anti-angiogenic therapy. A discussion on applicable clinical protocols is presented aiming to contribute to new insights into ophthalmology service development which is directed to this specific type of patient and diagnosis.

Morphological changes of macular neovascularization during long-term anti-VEGF-therapy in neovascular age-related macular degeneration

PURPOSE

To analyze the morphological changes of macular neovascularization (MNV) in exudative neovascular age-related macular degeneration under long-term intravitreal anti-vascular endothelial growth factor (VEGF) therapy in a retrospective cohort study.

METHODS AND PATIENTS

We evaluated 143 nAMD eyes of 94 patients (31 male, 63 female; initial age 55-97 y, mean age 75.9 ± 7.5 y), who started anti-VEGF therapy (IVAN pro re nata (PRN) protocol) between 2009-2018 and received ongoing therapy until the last recorded visit (mean follow-up 5.3 ± 2.9 y, range 1-14 y). The mean total number of injections was 33.3 ± 19.8 with 7.0 ± 2.3 injections/year. MNV size and, if present, associated complete retinal pigment epithelium (RPE) and outer retina atrophy (cRORA) size were measured on optical coherence tomography (OCT) volume scans at the initial visit and for each year of follow-up. MNV and cRORA were identified on B-scans and their respective borders were manually transposed onto the en-face near infrared image and measured in mm2.

RESULTS

MNV enlarged through follow-up, with a mean growth rate of 1.24 mm2 / year. The mean growth in MNV size was independent of initial MNV size, age, gender, MNV subtypes or number of injections per year. Nevertheless, a great interindividual variation in size and growth was observed. cRORA developed in association with increasing MNV size and its incidence increased linearly over follow-up. cRORA lesions also showed continuous growth by a rate of 1.22 mm2 / year.

CONCLUSIONS

Despite frequent long-term anti-VEGF therapy, we observed ongoing MNV growth. This is consistent with the concept that the development of MNV may be a physiological biological repair mechanism to preserve RPE and photoreceptor function, provided hyperpermeability and fluid exudation are controlled. Whether recurring low VEGF levels or other factors are responsible for MNV growth remains controversial.

Correlation of the OCT Double-Layer Sign with Type 1 Non-Exudative Neovascularization on OCT-A in Age-Related Macular Degeneration

Background and Objectives: Early diagnosis of the exudative form of age-related macular degeneration (AMD) is very important for a timely first treatment, which is directly related to the preservation of functional visual acuity over a long period. The goal of this paper was to examine the correlation between the double-layer sign (DLS) and the presence of non-exudative macular neovascularization (MNV). Materials and Methods: Our research included 60 patients with AMD, exudative in one eye and non-exudative in the other eye. We analyzed only the non-exudative form using optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A). The patients were classified into three groups, depending on the duration of the disease (<2 years, 2 to 5 years, >5 years). The onset of the disease was deemed the moment of establishing a diagnosis of exudative AMD in one eye. We defined the presence or absence of a DLS using OCT and the presence of non-exudative MNV using OCT-A, both on 3 × 3 mm and 6 × 6 mm sections. DLS was used as a projection biomarker for non-exudative MNV, with the aim of establishing a rapid diagnosis and achieving early treatment of the disease. Results: We found that there was a statistically significant correlation between the DLS diagnosed using OCT and non-exudative MNV diagnosed by OCT-A for both 3 × 3 mm (p < 0.001) and 6 × 6 mm (p < 0.001) imaging. There was a statistically significant difference between the frequencies of both DLS and MNV in Groups I and III on both 3 × 3 and 6 × 6 mm imaging. A statistically significant difference was also noted in the frequencies of DLS and MNV on 6 × 6 mm imaging, but not on 3 × 3 mm imaging, between Groups I and II. No differences were found between the frequencies of DLS and MNV between Groups II and III. Conclusions: The DLS on OCT can be used as a projection biomarker to assess the presence of a non-exudative MNV.

HISTOLOGY, DIMENSIONS, AND FLUORESCEIN STAINING CHARACTERISTICS OF NODULAR AND CUTICULAR DRUSEN IN AGE-RELATED MACULAR DEGENERATION

PURPOSE

To enable in vivo analysis of drusen composition and lifecycle, the macular nodular and cuticular drusen were assessed using histology.

METHODS

Median and interquartile range of base widths of single (nonconfluent) nodular drusen in three sources were determined histologically: 43 eyes of 43 clinically undocumented donors, in an online resource; one eye with punctate hyperfluorescence in fluorescein angiography; and two eyes of one patient with bilateral "starry sky" cuticular drusen. All tissues were processed for high-resolution epoxy-resin histology and for cuticular drusen, transmission electron microscopy.

RESULTS

All drusen localized between the retinal pigment epithelium basal lamina and inner collagenous layer of the Bruch membrane. They were solid, globular, homogeneously stained with toluidine blue, and uncovered by basal laminar deposit and basal mounds. Median base widths were 13.0 µ m (Source 1, N = 128 drusen, interquartile range 7.7, 20.0 µ m), 15.3 µ m (Source 2, N = 87, interquartile range 10.6, 20.5 µ m), and 7.3 µ m (Source 3, N = 78, interquartile range 3.9, 14.1 µ m).

CONCLUSION

In three samples, >90% of solitary nodular drusen were <30 µ m, the visibility threshold in color fundus photography; these drusen are hyperfluorescent in fluorescein angiography. Whether these progress to soft drusen, known as high-risk from epidemiology studies and hypofluorescent, may be determinable from multimodal imaging datasets that include fluorescein angiography.

Study protocol on prevalence of non-exudative macular neovascularisation and its contribution to prediction of exudation in fellow eyes with unilateral exudative AMD (EYE-NEON)

PURPOSE

Fellow eyes of patients with unilateral neovascular age-related macular degeneration (nAMD) are at risk of developing macular neovascularisation (MNV). These eyes may first develop subclinical non-exudative MNV (neMNV) before they leak to form exudative MNV (eMNV). The EYE NEON study is a 2-year study aimed at estimating the prevalence and incidence of neMNV and evaluating its role as a predictor for conversion to neovascular AMD.

METHODS

EYE NEON is a multicentre study that will run in retinal clinics across 25 National Health Service with the aim to recruit 800 patients with new onset nAMD in the first eye. The fellow-eye with no evidence of nAMD at baseline will be the study eye. All study eyes will have OCT and OCTA done at first and second year following first anti-VEGF treatment to the first eye (non-study eye), with new onset nAMD. We will estimate the prevalence and incidence of neMNV over 2 years, rate of conversion from neMNV to eMNV and numbers initiated on treatment for neovascular AMD in the study eye will be reported. Predictive models of conversion including neMNV with other demographic and imaging parameters will be developed.

CONCLUSION

The study design with proposed target sample size is sufficient to evaluate the retinal imaging characteristics of the study eyes with and without neMNV and develop predictive models to inform risk of conversion to nAMD.

Choriocapillaris Impairment Is Associated With Delayed Rod-Mediated Dark Adaptation in Age-Related Macular Degeneration

Purpose

Progress toward treatment and prevention of age-related macular degeneration (AMD) requires imaging end points that relate to vision. We investigated choriocapillaris flow signal deficits (FD%) and visual function in eyes of individuals aged ≥60 years, with and without AMD.

Methods

One eye of each participant in the baseline visit of the Alabama Study on Early Age-Related Macular Degeneration 2 (ALSTAR2; NCT04112667) was studied. AMD presence and severity was determined using the Age-Related Eye Disease Study (AREDS) grading system. FD% was quantified using macular spectral domain optical coherence tomography angiography (OCTA) scans. Vision tests included rod-mediated dark adaptation (RMDA), best-corrected visual acuity, and contrast sensitivity (photopic and mesopic), and microperimetric light sensitivity (scotopic, mesopic, and photopic). Presence of subretinal drusenoid deposits (SDD) was determined using multimodal imaging.

Results

In 410 study eyes of 410 participants (mean [SD] age = 71.7 years [5.9]), FD% was higher in early AMD (mean [SD] = 54.0% [5.5], N = 122) and intermediate AMD (59.8% [7.4], N = 92), compared to normal (52.1% [5.3], N = 196) eyes. Among visual functions evaluated, RMDA showed the strongest association with FD% (r = 0.35, P < 0.0001), followed by contrast sensitivity (r = -0.22, P < 0.0001). Eyes with SDD had worse FD% (58.3% [7.4], N = 87), compared to eyes without SDD (53.4% [6.0], N = 323, P = < 0.0001).

Conclusions

Choriocapillaris FD% were associated with AMD severity and with impaired vision, especially RMDA. Reduced metabolic transport and exchange across the choriocapillaris-Bruch's membrane retinal pigment epithelium (RPE) complex, a causal factor for high-risk soft drusen formation, also may impair photoreceptor sustenance from the circulation. This includes retinoid resupply, essential to dynamic rod function.

Characterisation of the vascular anterior surface of type 1 macular neovascularisation after anti-VEGF therapy

BACKGROUND

To evaluate whether the status of vasculature at the top of type 1 macular neovascularisation (MNV) could function as mediator of the observed protective effect against the development of complete retinal pigment epithelial and outer retinal atrophy (cRORA).

METHODS

In consecutive treatment-naïve patients, the vasculature at the anterior surface of the MNV was isolated using a slab designed to extract the most superficial vascular portion of the MNV lesion showing a choriocapillaris (CC)-like structure which we termed the 'neo-CC'. The ratio between the neo-CC area (isolated using this custom slab) and the MNV area (isolated using the standard outer retina-CC slab) at baseline and at last follow-up was evaluated.

RESULTS

Forty-four eyes from 44 patients were included. 20 showed cRORA by the final follow-up (median 23 months), whereas 24 did not progress to atrophy (median 23.5 months). The proportion of MNV with neo-CC at the anterior surface was significantly lower in eyes which progressed to cRORA compared with those which did not. The multivariate regression showed that a lower proportion of neo-CC coverage over the MNV was associated with an increased odds for cRORA development.

CONCLUSIONS

More extensive coverage of neo-CC is associated with a lower likelihood of development of macular atrophy in eyes receiving antivascular endothelial growth factor therapy, suggesting the protective effect of a type 1 MNV may be mediated by the development of a neo-CC and may provide insights into the biological significance of MNV as a response mechanism in eyes with age-related macular degeneration.

Growth of nonexudative macular neovascularization in age-related macular degeneration: an indicator of biological lesion activity

PURPOSE

To investigate the growth of nonexudative macular neovascularization (MNV) in age-related macular degeneration (AMD) using swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

Patients with treatment-naïve nonexudative AMD in one eye and exudative AMD in the fellow eye who underwent SS-OCTA imaging for at least 12 months were retrospectively reviewed. The MNV area measurement was quantified in eyes with treatment-naïve nonexudative MNV using ImageJ for analysing the correlation between MNV growth and the onset of exudation, as well as evaluating the consistency of the MNV growth rate during the subclinical and exudative stages. Kaplan-Meier survival analysis and logistic regression analyses were used.

RESULTS

In total, 45 eyes with treatment-naïve nonexudative AMD from 45 patients were enrolled. Treatment-naïve nonexudative MNV was identified in 21 eyes (46.67%) at baseline. The development of exudative findings was noted in eight eyes (17.78%), including six eyes with previously noted nonexudative MNV. Eyes with growing MNV (increase in area ≥50% within 12 months) had an increased risk of exudation and developed exudation earlier than eyes with stable MNV (13.60 [6.43-20.77] months versus 31.11 [26.61-35.62] months, P < 0.0001, Log-rank test). Consistent growth pattern of MNV lesions was further identified in eyes with growing MNV during anti-VEGF treatment.

CONCLUSION

SS-OCTA allows to qualitatively and quantitatively evaluate nonexudative MNV in AMD patients. Growing MNV involved higher probabilities and a faster onset of exudation compared to stable MNV. Identifying the growth of MNV on OCTA might be helpful for establishing treatment strategies and follow-up planning.

OPTICAL COHERENCE TOMOGRAPHY FEATURES RELEVANT TO NEOVASCULAR AGE-RELATED MACULAR DEGENERATION MANAGEMENT AND NONNEOVASCULAR AGE-RELATED MACULAR DEGENERATION PROGRESSION: CLINICOPATHOLOGIC CORRELATION

PURPOSE

Clinicopathologic correlation of two optical coherence tomography (OCT) features in neovascular age-related macular degeneration.

METHODS

Case report, clinicopathologic correlation.

RESULTS

A patient in her 90s was diagnosed with Type 3 macular neovascularization secondary to age-related macular degeneration in the index right eye and underwent intravitreal antivascular endothelial growth factor treatment for 5 years. A double-layer sign on in vivo OCT was correlated to calcified drusen on histology. Furthermore, hyperfluorescence on fluorescein angiography corresponded on histology to choroidal hypertransmission on OCT and retinal pigment epithelium atrophy above calcified drusen.

CONCLUSION

A double-layer sign on OCT can represent nonneovascular subretinal pigment epithelium material including wide and flat calcific nodules. Furthermore, hyperfluorescence on FA, among different origins, can be due to a window defect corresponding to retinal pigment epithelium atrophy, which can be confirmed with OCT. Clinicopathological correlation using high-resolution histology can demonstrate the fine details available to clinical decision making through currently available in vivo OCT imaging.

SUBRETINAL LIPID GLOBULES AN EARLY BIOMARKER OF MACULAR NEOVASCULARIZATION IN EYES WITH INTERMEDIATE AGE-RELATED MACULAR DEGENERATION

PURPOSE

To explore the association between subretinal lipid globules (SLGs) detected in eyes with intermediate age-related macular degeneration with the presence of nonexudative macular neovascularization.

METHODS

This was a retrospective analysis of 113 consecutive patients with bilateral intermediate age-related macular degeneration (226 eyes) followed for a least 6 months. All eyes underwent multimodal imaging with fundus autofluorescence, spectral-domain optical coherence tomography, and optical coherence tomography angiography. Subretinal lipid globules were identified on spectral-domain optical coherence tomography as round hyporeflective lesions measuring 31 to 157 µ m located between the ellipsoid zone and the retinal pigment epithelium/Bruch membrane complex. Nonexudative macular neovascularization was detected with optical coherence tomography angiography. The features of NE-MNV lesions detected in eyes with SLGs were compared with those in eyes without SLGs.

RESULTS

Subretinal lipid globules were identified in 15 eyes of which 14 eyes (93.3%) demonstrated NE-MNV on optical coherence tomography angiography. In the remaining 98 eyes without SLGs, 18 (18.4%) displayed NE-AMD on optical coherence tomography angiography. The macular neovascularization area was larger in the SLG subgroup (+0.38 vs. +0.21 mm 2 , P = 0.008) and showed faster horizontal growth (+727 µ m, CI 95% 250.4, 1,205.4) than MNV in eyes without SLGs (+64.9 µ m, CI 95%, 24.3, 154) on optical coherence tomography B-scans. After a mean of 11.6 months, the conversion rate to exudative MNV was similar between eyes with SLGs and those without SLGs [8/26 (38.5%) versus 3/13 (27.3%), P = 0.56)].

CONCLUSION

The detection of SLGs in eyes with intermediate age-related macular degeneration was strongly correlated with the presence of NE-MNV. Although these MNV lesions were larger and grew faster than NE-MNV detected in eyes lacking SLGs, the rates of conversion to exudative MNV appeared similar.

Quantitative assessment of choriocapillaris flow deficits and type 1 macular neovascularization growth in age-related macular degeneration

During the past 15 years, new treatment paradigms for neovascular age-related macular degeneration (nvAMD) have evolved due to the advent of intravitreal anti-vascular endothelial growth factor (VEGF) therapy and rapid advances in retinal imaging. Recent publications describe eyes with type 1 macular neovascularization (MNV) as showing more resistance to macular atrophy than eyes with other lesion types. We sought to explore whether the perfusion status of the native choriocapillaris (CC) surrounding type 1 MNV influences its pattern of growth. To evaluate this effect, we analyzed a case series of 22 eyes from 19 nvAMD patients with type 1 MNV exhibiting growth on swept-source optical coherence tomography angiography (SS-OCTA) over a minimum follow-up of 12 months. We observed an overall weak correlation between type 1 MNV growth and CC flow deficits (FDs) average size (τ = 0.17, 95% CI [- 0.20, 0.62]) and a moderate correlation with CC FD % (τ = 0.21, 95% CI [- 0.16, 0.68]). Type 1 MNV was located beneath the fovea in most of the eyes (86%) and median visual acuity was 20/35 Snellen equivalent. Our results support that type 1 MNV recapitulates areas of CC blood flow impairment while serving to preserve foveal function.

Rethinking the potential and necessity of drug delivery systems in neovascular age-related macular degeneration therapy

Age-related macular degeneration (AMD) is the predominant threat to human vision and ultimately results in blindness. With the increase in the aging population, it has become a more crucial issue to human health. AMD is a multifactorial disease with the unique feature of uncontrollable angiogenesis during initiation and progression. Although increasing evidence indicates that AMD is largely hereditary, the predominant efficient treatment is antiangiogenesis, which mainly involves VEGF and HIF-α as therapeutic targets. The repeated administration of this treatment over the long term, generally through intravitreal injection, has called for the introduction of long-term drug delivery systems, which are expected to be achieved by biomaterials. However, the clinical results of the port delivery system indicate that the optimization of medical devices toward prolonging the activities of therapeutic biologics in AMD therapy seems more promising. These results indicate that we should rethink the possibility and potential of biomaterials as drug delivery systems in achieving long-term, sustained inhibition of angiogenesis in AMD therapy. In this review, the etiology, categorization, risk factors, pathogenesis, and current clinical treatments of AMD are briefly introduced. Next, the development status of long-term drug delivery systems is discussed, and the drawbacks and shortages of these systems are emphasized. By comprehensively considering the pathological aspect and the recent application of drug delivery systems in AMD therapy, we hope to find a better solution for the further development of long-term therapeutic strategies for AMD.

OCT Risk Factors for Development of Atrophy in Eyes with Intermediate Age-Related Macular Degeneration

PURPOSE

To determine the frequency of multiple OCT biomarkers of intermediate age-related macular degeneration (iAMD) and their relationship with the development of complete retinal pigment epithelium and outer retinal atrophy (cRORA) after 2 years.

DESIGN

Retrospective cohort study.

PARTICIPANTS

This retrospective analysis included 330 eyes of 330 consecutive patients with iAMD in ≥ 1 eye who had 24 months of follow-up data.

METHODS

Spectralis OCT volume scans (49 B-scans over 6 × 6 mm, automatic real time = 6, fovea-centered) at baseline were evaluated for the previously described iAMD biomarkers, including a high-central drusen volume (DV; ≥ 0.03 mm³), intraretinal hyper-reflective foci (IHRF), subretinal drusenoid deposits (SDDs), hypo-reflective drusen cores (hDCs), and a thin or thick (multilayered) double-layer sign (DLS). The age-related macular degeneration (AMD) status in the fellow eye was also assessed and classified as normal or early AMD, iAMD, exudative macular neovascularization, or cRORA.

MAIN OUTCOME MEASURES

Incidence of cRORA, odds ratio for demographics, and OCT features.

RESULTS

At month 24, 16.36% (54/330) of the iAMD eyes developed cRORA. Several baseline features, including high-central DV, IHRF, SDD, hDC, thin DLS, and cRORA in the fellow eye, were associated with a significantly greater risk for development of cRORA at 2 years. The odds ratio, 95% confidence interval, P value, and baseline frequencies of these biomarkers were DV (6.510, 2.467-17.176, P < 0.001, 49.1%), IHRF (12.763, 4.763-34.202, P < 0.001, 38.8%), SDD (2.307, 1.003-5.304, P = 0.049, 34.2%), hDC (3.012, 1.152-7.873, P = 0.024, 13.0%), thin DLS (4.517, 1.555-13.126, P = 0.006, 11.8%), and cRORA in the fellow eye (7.184, 1.938-26.623, P = 0.003, 8.2%).

CONCLUSIONS

In addition to the 4 previously reported factors that are present in a significant proportion of iAMD (DV, IHRF, hDC, and SDD), a thin DLS and cRORA in the fellow eye were associated with an increased risk of progression to cRORA over 2 years. These biomarkers may aid in prognostication, risk stratification, and selection of patients for clinical trials.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Histology of type 3 macular neovascularization and microvascular anomalies in treated age-related macular degeneration: a case study

Purpose

To investigate intraretinal neovascularization and microvascular anomalies by correlating in vivo multimodal imaging with corresponding ex vivo histology in a single patient.

Design

A case study comprising clinical imaging from a community-based practice, and histologic analysis at a university-based research laboratory (clinicopathologic correlation).

Participants

A White woman in her 90s treated with numerous intravitreal anti-VEGF injections for bilateral type 3 macular neovascularization (MNV) secondary to age-related macular degeneration (AMD).

Methods

Clinical imaging comprised serial infrared reflectance, eye-tracked spectral-domain OCT, OCT angiography, and fluorescein angiography. Eye tracking, applied to the 2 preserved donor eyes, enabled the correlation of clinical imaging signatures with high-resolution histology and transmission electron microscopy.

Main Outcome Measures

Histologic/ultrastructural descriptions and diameters of vessels seen in clinical imaging.

Results

Six vascular lesions were histologically confirmed (type 3 MNV, n = 3; deep retinal age-related microvascular anomalies [DRAMAs], n = 3). Pyramidal (n = 2) or tangled (n = 1) morphologies of type 3 MNV originated at the deep capillary plexus (DCP) and extended posteriorly to approach without penetrating persistent basal laminar deposit. They did not enter the subretinal pigment epithelium (RPE)-basal laminar space or cross the Bruch membrane. Choroidal contributions were not found. The neovascular complexes included pericytes and nonfenestrated endothelial cells, within a collagenous sheath covered by dysmorphic RPE cells. Deep retinal age-related microvascular anomaly lesions extended posteriorly from the DCP into the Henle fiber and the outer nuclear layers without evidence of atrophy, exudation, or anti-VEGF responsiveness. Two DRAMAs lacked collagenous sheaths. External and internal diameters of type 3 MNV and DRAMA vessels were larger than comparison vessels in the index eyes and in aged normal and intermediate AMD eyes.

Conclusions

Type 3 MNV vessels reflect specializations of source capillaries and persist during anti-VEGF therapy. The collagenous sheath of type 3 MNV lesions may provide structural stabilization. If so, vascular characteristics may be useful in disease monitoring in addition to fluid and flow signal detection. Further investigation with longitudinal imaging before exudation onset will help determine if DRAMAs are part of the type 3 MNV progression sequence.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

[Diagnosis and clinical features of non-exudative macular neovascularization]

Macular neovascularization (MNV) is the process of new abnormal blood vessels formation in the choroid and/or retina. The widespread adoption of optical coherence tomography angiography (OCTA) has significantly expanded the possibilities of not only detecting pathological blood flow before the development of exudation and deterioration of visual acuity, but also determining its characteristics. The purpose of this review is to substantiate the criteria for choosing terminology and diagnostic markers of MNV. The term "non-exudative MNV" refers to type 1 neovascularization without intraretinal or subretinal exudation detected on repeated OCT scans in the course of at least 6 months. This type of MNV may include previously untreated, non-exudative membranes with a low tendency to exudate, as well as previously treated membranes that have become inactive or dormant and no longer require anti-angiogenic therapy. The criterion for dividing the non-exudative form of MNV into inactive (with a low growth rate and vascular density (VD) at baseline) and subclinical (with a high growth rate and VD) is the time of its activation, generally recognized as 6 months. The diagnostic criteria is the visualized "double layer" sign on OCT scans (retinal pigment epithelium and Bruch's membrane), as well as patterns of neovascular membranes of varying sizes, morphology and localization on OCTA scans. The cumulative risk of conversion from subclinical to exudative at two years of follow-up is 13.6 times higher than in eyes without detectable neovascularization, which highlights the importance of frequent monitoring in this healthy eye population for early detection of MNV signs.

Towards a better understanding of non-exudative choroidal and macular neovascularization

Non-exudative macular and choroidal neovascularization (MNV and CNV) usually refers to the entity of treatment-naïve type 1 neovascularization in the absence of associated signs of exudation. Histopathological studies, dating back in the early 70s, identified the presence of non-exudative MNV, but the first clinical report of this finding was in the late 90s using indocyanine green angiography in eyes with age-related macular degeneration (AMD). With more advanced retinal imaging, there has been an ever increasing appreciation of non-exudative MNV associated with AMD and CNV with other macular disorders. However, consensus regarding the exact definition and the clinical management of this entity is lacking. Furthermore, there may be variation in the imaging features and clinical course suggesting that a spectrum of disease may exist. Herein, we review the large body of published work that has provided a better understanding of non-exudative MNV and CNV in the last decade. The prevalence, multimodal imaging features, clinical course, and response to treatment are discussed to elucidate further key insights about this entity. Based on these observations, this review also proposes a new theory about the origin and course of different sub-types of non-exudative MNV/CNV which can have different etiologies and pathways according to the clinical context of disease.

The Essential Role of the Choriocapillaris in Vision: Novel Insights from Imaging and Molecular Biology

The choriocapillaris, a dense capillary network located at the posterior pole of the eye, is essential for supporting normal vision, supplying nutrients, and removing waste products from photoreceptor cells and the retinal pigment epithelium. The anatomical location, heterogeneity, and homeostatic interactions with surrounding cell types make the choroid complex to study both in vivo and in vitro. Recent advances in single-cell RNA sequencing, in vivo imaging, and in vitro cell modeling are vastly improving our knowledge of the choroid and its role in normal health and in age-related macular degeneration (AMD). Histologically, loss of endothelial cells (ECs) of the choriocapillaris occurs early in AMD concomitant with elevated formation of the membrane attack complex of complement. Advanced imaging has allowed us to visualize early choroidal blood flow changes in AMD in living patients, supporting histological findings of loss of choroidal ECs. Single-cell RNA sequencing is being used to characterize choroidal cell types transcriptionally and discover their altered patterns of gene expression in aging and disease. Advances in induced pluripotent stem cell protocols and 3D cultures will allow us to closely mimic the in vivo microenvironment of the choroid in vitro to better understand the mechanism leading to choriocapillaris loss in AMD.

Visualizing lipid behind the retina in aging and age-related macular degeneration, via indocyanine green angiography (ASHS-LIA)

Age-related macular degeneration (AMD) causes legal blindness in older adults worldwide. Soft drusen are the most extensively documented intraocular risk factor for progression to advanced AMD. A long-standing paradox in AMD pathophysiology has been the vulnerability of Asian populations to polypoidal choroidal vasculopathy (PCV) in the presence of relatively few drusen. Age-related scattered hypofluorescent spots on late phase indocyanine green angiography (ASHS-LIA) was recently proposed as precursors of PCV. Herein, we offer a resolution to the paradox by reviewing evidence that ASHS-LIA indicates the diffuse form of lipoprotein-related lipids accumulating in Bruch's membrane (BrM) throughout adulthood. Deposition of these lipids leads to soft drusen and basal linear deposit (BLinD), a thin layer of soft drusen material in AMD; Pre-BLinD is the precursor. This evidence includes: 1. Both ASHS-LIA and pre-BLinD/BLinD accumulate in older adults and start under the macula; 2. ASHS-LIA shares hypofluorescence with soft drusen, known to be physically continuous with pre-BLinD/BLinD. 3. Model system studies illuminated a mechanism for indocyanine green uptake by retinal pigment epithelium. 4. Neither ASHS-LIA nor pre-BLinD/ BLinD are visible by multimodal imaging anchored on current optical coherence tomography, as confirmed with direct clinicopathologic correlation. To contextualize ASHS-LIA, we also summarize angiographic characteristics of different drusen subtypes in AMD. As possible precursors for PCV, lipid accumulation in forms beyond soft drusen may contribute to the pathogenesis of this prevalent disease in Asia. ASHS-LIA also might help identify patients at risk for progression, of value to clinical trials for therapies targeting early or intermediate AMD.

Association between retinal sensitivity and the presence of quiescent choroidal neovascularization in pachychoroid diseases

This study was conducted to examine retinal sensitivity (RS) in eyes with pachychoroid diseases and to analyze its association with the presence or absence of quiescent choroidal neovascularization (CNV), that can be protective against retinal dysfunction or atrophy in other macular diseases such as age-related macular degeneration. A total of 12 eyes of 12 patients aged ≥45 years having the characteristic findings of central serous chorioretinopathy but not presenting any exudative changes were included in this study. Choroidal vascular hyper permeability (CVH) was identified by indocyanine green angiography, and the presence or absence of CNV was evaluated by optical coherence tomography angiography. RS at 68 points was examined by microperimetry. The average RS corresponding to within and outside CVH was compared. The association between the difference in RS and the presence or absence of CNV was also analyzed. CNV was detected in six eyes (50%). In eyes without CNV, the RS within CVH was similar compared with that outside CVH. However, in eyes with CNV, the RS within CVH was significantly decreased compared with that outside CVH. Multiple regression analysis revealed the presence of CNV as an independent factor associated with RS. In eyes with pachychoroid diseases, RS decreased within the CVH area under the coexistence of nonexudative CNV.

Relationship between retinal fluid characteristics and vision in neovascular age-related macular degeneration: HARBOR post hoc analysis

Purpose

To evaluate the relationship between retinal fluid location, amount/severity, and vision with ranibizumab-treated neovascular age-related macular degeneration (nAMD).

Methods

In the phase 3 HARBOR trial (NCT00891735), treatment-naive patients with nAMD received ranibizumab 0.5 or 2.0 mg through month 24. This post hoc analysis included eyes with subretinal fluid (SRF) and/or intraretinal fluid (IRF) at screening, baseline, or week 1, and optical coherence tomography data at months 12 and 24 (n = 917). Outcomes were best-corrected visual acuity (BCVA) change from baseline and proportion of eyes with 20/40 or better vision at months 12 and 24. Eyes were stratified by the location, amount, and/or severity of fluid.

Results

At baseline, 86% and 63% of eyes had SRF and IRF, respectively. Among eyes with residual SRF, mean BCVA gains at each time point were greater in eyes with central versus noncentral SRF; location did not affect the odds of having 20/40 or better vision over 24 months. Eyes with 20/40 or better BCVA at month 12 had significantly lower SRF thickness versus eyes with worse vision; however, no difference was apparent at month 24. Vision was comparatively worse in eyes with residual IRF at months 12 and 24; location and severity did not appear to affect this outcome.

Conclusion

Residual IRF was associated with worse vision outcomes, regardless of location/severity, whereas, despite continued treatment, residual SRF was not associated with worse vision outcome at 24 months, regardless of location/thickness. These data suggest complex relationships between residual fluid, severity, and vision.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-022-05716-4.

Differences in long-term progression of atrophy between neovascular and non-neovascular age-related macular degeneration

PURPOSE

To compare enlargement rates over 5 years of follow-up in geographic atrophy (GA) versus macular atrophy (MA) associated with macular neovascularization (MNV).

DESIGN

Retrospective, longitudinal comparative case series.

PARTICIPANTS

Consecutive series of age-related macular degeneration (AMD) patients with GA (dry) or MA with MNV.

METHODS

Atrophic regions on serial registered fundus autofluorescence (FAF) images were semiautomatically delineated and area measurements were recorded every 6±3 months for the first 2 years of follow-up and at yearly intervals up to 5 years.

MAIN OUTCOME MEASURES

Annual raw and square root transformed atrophy growth rates.

RESULTS

117 eyes of 95 patients were included (61 in the GA and 56 in the MA cohort); 100% and 38.5% of eyes completed 2 and 5 years of follow-up, respectively. Mean baseline lesion size was similar between the two groups (raw: 1.74 vs. 1.53 mmˆ2, p = 0.56; sqrt transformed: 1.17 vs. 1.02 mm, p = 0.26). Overall enlargement rates were greater for the GA cohort (raw: 1.72 vs. 1.32 mmˆ2/year, p = 0.002; sqrt transformed: 0.41 vs. 0.33 mm/year; p = 0.03), as well as the area of atrophy growth at 5 years (raw: +8.06 vs. +4.55 mmˆ2, p = 0.001; sqrt transformed: +1.93 vs. +1.38 mm, p = 0.02). Estimated sqrt transformed area was also significantly greater for the GA cohort at 2 years (1.84 vs. 1.67 mm, p = 0.01).

CONCLUSIONS

Presence of MNV was associated with a slower rate of expansion resulting in overall smaller areas of atrophy over time. These findings support the hypothesis that MNV may protect against the progression of atrophy.

Neovascular age-related macular degeneration: advancement in retinal imaging builds a bridge between histopathology and clinical findings

PURPOSE

To provide a review of the salient histological and imaging features in neovascular age-related macular degeneration (AMD) that will be integrated in order to have a better comprehension of the pathogenesis and clinical aspects of this disease.

METHODS

A literature review of histology and imaging features in neovascular AMD was conducted.

RESULTS

Histology has granted a detailed characterization of neovascular AMD ex vivo. In details, histological features in these eyes have offered important insights into the pathogenesis of neovascular AMD. In addition, histology donated a detailed characterization of the different types of macular neovascularization (MNV) that may complicate AMD. The introduction of optical coherence tomography angiography (OCTA) has enormously amplified our knowledge of neovascular AMD through in vivo assessment of the anatomical and pathological characteristics of this disease. New insights elucidating the morphological features of the choriocapillaris confirmed that this vascular structure plays a crucial role in the pathogenesis of neovascular AMD. OCTA also offered a detailed visualization of MNV complicating neovascular AMD.

CONCLUSIONS

New imaging technologies offer a remarkable chance to build a bridge between histology and clinical findings in neovascular AMD.

Difference Between the Incidence of Retinal Fluid Subtypes and Their Association with Visual Outcomes According to the Types of Macular Neovascularization in a Korean Population

Purpose: To investigate differences in the incidence of retinal fluid subtypes among different subtypes of macular neovascularization (MNV) and evaluate the influence of the presence of retinal fluid subtypes on visual outcome in each subtype of MNV. Methods: This retrospective study included 248 patients (248 eyes) diagnosed with treatment-naive neovascular age-related macular degeneration and polypoidal choroidal vasculopathy (PCV). The incidence of retinal fluid subtypes at diagnosis and during the 24-month follow-up was compared among the different subtypes of MNV. In addition, visual acuity was compared between patients with and without the retinal fluid subtypes. Results: At diagnosis, there was a significant difference in the incidence of subretinal fluid (SRF), intraretinal fluid (IRF), and subretinal pigment epithelial fluid among type 1 MNV, type 2 MNV, type 3 MNV, and PCV (P < 0.001). The incidence of SRF (P < 0.001) during follow-up also differed among the 4 groups. In patients with type 1 MNV and IRF, the visual acuity at diagnosis (P = 0.004) and at 24 months (P < 0.001) were significantly worse. However, the presence of SRF was not associated with poor visual acuity. In type 3 MNV, there was no significant difference in visual acuity between patients with and without SRF/IRF. Conclusion: The results of this study indicate that the clinical significance of retinal fluid subtypes may differ in different subtypes of MNV, suggesting the need for analysis in isolation of each MNV subtype in fluid-based prognostication.

Spatial Dissociation of Subretinal Drusenoid Deposits and Impaired Scotopic and Mesopic Sensitivity in AMD

Purpose

Subretinal drusenoid deposits (SDD) first appear in the rod-rich perifovea and can extend to the cone-rich fovea. To refine the spatial relationship of visual dysfunction with SDD burden, we determined the topography of mesopic and scotopic light sensitivity in participants with non-neovascular AMD with and without SDD.

Methods

Thirty-three subjects were classified into three groups: normal (n = 9), AMD-Drusen (with drusen and without SDD; n = 12), and AMD-SDD (predominantly SDD; n = 12). Mesopic and scotopic microperimetry were performed using 68 targets within the Early Treatment Diabetic Retinopathy Study grid, including points at 1.7° from the foveal center (rod:cone ratio, 0.35). Age-adjusted linear regression was used to compare mesopic and scotopic light sensitivities across groups.

Results

Across the entire Early Treatment Diabetic Retinopathy Study grid and within individual subfields, the three groups differed significantly for mesopic and scotopic light sensitivities (all P < 0.05). The AMD-SDD group exhibited significantly decreased mesopic and scotopic sensitivity versus both the normal and the AMD-Drusen groups (all P < 0.05), while AMD-Drusen and normal eyes did not significantly differ (all P > 0.05). The lowest relative sensitivities were recorded for scotopic light levels, especially in the central subfield, in the AMD-SDD group.

Conclusions

SDD-associated decrements in rod-mediated vision can be detected close to the foveola, and these deficits are proportionately worse than functional loss in the rod-rich perifovea. This finding suggests that factors other than the previously hypothesized direct cytotoxicity to photoreceptors and local transport barrier limitations may negatively impact vision. Larger prospective studies are required to confirm these observations.

Pigmentary abnormality without significant drusen as a risk factor for late age-related macular degeneration

We investigated the incidence and risk factors of late age-related macular degeneration (AMD) in the fellow eye (FE) without significant drusen of patients with unilateral exudative macular neovascularization (MNV). In this retrospective study, 241 eligible patients who were followed-up for more than 3 years were enrolled. We analyzed the incidence and hazard ratios (HRs) of late AMD in the FE according to demographic and ophthalmologic variables. Hypopigmentation on color fundus photography (CFP) corresponds to shallow irregular RPE elevation (SIRE), so-called "double-layer sign" and/or "attenuation or disruption of RPE and/or ellipsoid zone" on OCT. The 5-year incidence of FE exudative MNV conversion was 8.6%. The 5-year incidence of FE exudative MNV of large hypopigmentation (≥ 0.5 disc area; DA) and small hypopigmentation (< 0.5 DA) on CFP, and SIRE (≥ 1000 µm) and small RPE elevation (< 1000 µm) on OCT were 36.2%, 14.2%, 55.0%, and 15.6%, respectively. The multivariate Cox proportional hazard model revealed that large hypopigmentation, small hypopigmentation, SIRE, and small RPE elevation showed HRs of 23.230, 8.037, 132.589, and 41.823 for FE exudative MNV occurrence, respectively. Hypopigmentation on CFP and SIRE on OCT could represent the same lesion. Even small hypopigmentation and small RPE elevation were significant risk factors for progression to exudative MNV.

Histology and clinical imaging lifecycle of black pigment in fibrosis secondary to neovascular age-related macular degeneration

PURPOSE

Melanotic cells with large spherical melanosomes, thought to originate from retinal pigment epithelium (RPE), are found in eyes with neovascular age-related macular degeneration (nvAMD). To generate hypotheses about RPE participation in fibrosis, we correlate histology to clinical imaging in an eye with prominent black pigment in fibrotic scar secondary to nvAMD.

METHODS

Macular findings in a white woman with untreated inactive subretinal fibrosis due to nvAMD in her right eye were documented over 9 years with color fundus photography (CFP), fundus autofluorescence (FAF) imaging, and optical coherence tomography (OCT). After death (age 90 years), this index eye was prepared for light and electron microscopy to analyze 7 discrete zones of pigmentation in the fibrotic scar. In additional donor eyes with nvAMD, we determined the frequency of black pigment (n = 36 eyes) and immuno-labeled for retinoid, immunologic, and microglial markers (RPE65, CD68, Iba1, TMEM119; n = 3 eyes).

RESULTS

During follow-up of the index eye, black pigment appeared and expanded within a hypoautofluorescent fibrotic scar. The blackest areas correlated to melanotic cells (containing large spherical melanosomes), some in multiple layers. Pale areas had sparse pigmented cells. Gray areas correlated to cells with RPE organelles entombed in the scar and multinucleate cells containing sparse large spherical melanosomes. In 94% of nvAMD donor eyes, hyperpigmentation was visible. Certain melanotic cells expressed some RPE65 and mostly CD68. Iba1 and TMEM119 immunoreactivity, found both in retina and scar, did not co-localize with melanotic cells.

CONCLUSION

Hyperpigmentation in CFP results from both organelle content and optical superimposition effects. Black fundus pigment in nvAMD is common and corresponds to cells containing numerous large spherical melanosomes and superimposition of cells containing sparse large melanosomes, respectively. Melanotic cells are molecularly distinct from RPE, consistent with a process of transdifferentiation. The subcellular source of spherical melanosomes remains to be determined. Detailed histology of nvAMD eyes will inform future studies using technologies for spatially resolved molecular discovery to generate new therapies for fibrosis. The potential of black pigment as a biomarker for fibrosis can be investigated in clinical multimodal imaging datasets.

Retinal Progression Biomarkers of Early and Intermediate Age-Related Macular Degeneration

Early and intermediate AMD patients represent a heterogeneous population with an important but variable risk of progression to more advanced stages of the disease. The five-year progression from early and intermediate AMD to late disease is known to range from 0.4% to 53%. This wide variation explains the particular interest in searching predictive AMD biomarkers. Clinical parameters such as drusen size, presence of pigmentary abnormalities, and fellow eye status were, traditionally, the more important predictive elements. Multimodal retinal assessment (Color Fundus Photography, Optical Coherence Tomography, Optical Coherence Angiography and Fundus Autofluorescence) is providing new and accurate image biomarkers, useful in research and in daily practice. If individual progression risk could be anticipated, then management plans should be adapted accordingly, considering follow-up intervals and therapeutic interventions. Here, we reviewed the most important image progression biomarkers of early and intermediate AMD with relevant interest in clinical practice.

MASSIVE ADVANCING NONEXUDATIVE TYPE 1 CHOROIDAL NEOVASCULARIZATION IN CTRP5 LATE-ONSET RETINAL DEGENERATION: Longitudinal Findings on Multimodal Imaging and Implications for Age-Related Macular Degeneration

PURPOSE

To describe longitudinal multimodal imaging findings of nonexudative choroidal neovascularization in CTRP5 late-onset retinal degeneration.

METHODS

Four patients with CTRP5-positive late-onset retinal degeneration underwent repeated ophthalmoscopic examination and multimodal imaging. All four patients (two siblings and their cousins, from a pedigree described previously) had the heterozygous S163R mutation.

RESULTS

All four patients demonstrated large subretinal lesions in the mid-peripheral retina of both eyes. The lesions were characterized by confluent hypercyanescence with hypocyanescent borders on indocyanine green angiography, faintly visible branching vascular networks with absent/minimal leakage on fluorescein angiography, Type 1 neovascularization on optical coherence tomography angiography, and absent retinal fluid, consistent with nonexudative choroidal neovascularization. The neovascular membranes enlarged substantially over time and the birth of new membranes was observed, but all lesions remained nonexudative/minimally exudative. Without treatment, all involved retinal areas remained free of atrophy and subretinal fibrosis.

CONCLUSION

We report the existence of massive advancing nonexudative Type 1 choroidal neovascularization in CTRP5 late-onset retinal degeneration. These findings have implications for age-related macular degeneration. They provide a monogenic model system for studying the mechanisms underlying the distinct events of choroidal neovascularization development, enlargement, progression to exudation, and atrophy in age-related macular degeneration. They suggest that choroidal hypoperfusion precedes neovascularization and that nonexudative neovascularization may protect against atrophy.

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.

Physics-based modeling of Age-related Macular Degeneration-A theoretical approach to quantify retinal and choroidal contributions to macular oxygenation

We developed a mathematical model to characterize how macular oxygenation may be affected by abnormalities in the retinal and choroidal oxygen supplies. The macular region is modeled as a layered structure including: ganglion cell and nerve fiber layers, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, inner segment of photoreceptors layer and retinal pigmented epithelium. Each layer is characterized by specific levels of oxygen consumption. The vitreous and the choroid are located at the macula boundary and provide oxygen via boundary conditions of Dirichlet type. The three capillary plexi (superficial, intermediate, and deep) of the retinal circulation pierce the macular layers and provide oxygen via a volumetric source that depends on the retinal blood flow. Oxygen profiles through the macular tissue are calculated by simulating the balance among oxygen supply, consumption and diffusion in: (a) physiological baseline conditions; (b) retinal blood flow reduced by 10%, 30% and 50% with respect to baseline; (c) choroidal oxygen level diminished by 10%, 30% and 50% with respect to baseline. Model simulations predict that: (1) the oxygenation of the foveal avascular zone is not affected by reduction in retinal blood flow; (2) a reduction in choroidal oxygen supply significantly affects the outer layers, especially the photoreceptors and outer nuclear layers; (3) the impact of reduction in choroidal oxygen supply is larger in the region more proximal to the macular center; (4) the impact of reduction in retinal blood flow is larger in the region more proximal to the macular periphery. The proposed mathematical model suggests that changes in retinal and choroidal oxygen supplies impact the oxygenation of the macular tissue differentially. These results may help better understand the pathogenesis of macular degeneration.

AI-based monitoring of retinal fluid in disease activity and under therapy

Retinal fluid as the major biomarker in exudative macular disease is accurately visualized by high-resolution three-dimensional optical coherence tomography (OCT), which is used world-wide as a diagnostic gold standard largely replacing clinical examination. Artificial intelligence (AI) with its capability to objectively identify, localize and quantify fluid introduces fully automated tools into OCT imaging for personalized disease management. Deep learning performance has already proven superior to human experts, including physicians and certified readers, in terms of accuracy and speed. Reproducible measurement of retinal fluid relies on precise AI-based segmentation methods that assign a label to each OCT voxel denoting its fluid type such as intraretinal fluid (IRF) and subretinal fluid (SRF) or pigment epithelial detachment (PED) and its location within the central 1-, 3- and 6-mm macular area. Such reliable analysis is most relevant to reflect differences in pathophysiological mechanisms and impacts on retinal function, and the dynamics of fluid resolution during therapy with different regimens and substances. Yet, an in-depth understanding of the mode of action of supervised and unsupervised learning, the functionality of a convolutional neural net (CNN) and various network architectures is needed. Greater insight regarding adequate methods for performance, validation assessment, and device- and scanning-pattern-dependent variations is necessary to empower ophthalmologists to become qualified AI users. Fluid/function correlation can lead to a better definition of valid fluid variables relevant for optimal outcomes on an individual and a population level. AI-based fluid analysis opens the way for precision medicine in real-world practice of the leading retinal diseases of modern times.

Progression of macular atrophy in patients undergoing anti-vascular endothelial growth factor therapy for neovascular age-related macular degeneration

PURPOSE

To assess differences in the progression of macular atrophy (MA) between neovascular age-related macular degeneration (AMD) subtypes and to identify the risk factors associated with the foveal involvement among patients with MA undergoing long-term anti-vascular endothelial growth factor (VEGF) treatment.

METHODS

Eighty eyes of 80 patients with neovascular AMD who developed incident MA following anti-VEGF therapy were retrospectively included. Macular atrophy (MA) was quantified using autofluoresence (AF) images within 24 months after the onset of MA, and the enlargement rate was compared between neovascular AMD subtypes. Regression models were constructed to explore relationships between foveal involvement in MA and baseline characteristics.

RESULTS

The growth rate of MA was 0.18 mm² /year for type 1 neovascularization (NV), 0.24 mm² /year for type 2 NV, and 1.21 mm² /year for type 3 NV; differences between groups were significant (p = 0.022). Multivariate logistic regression analysis revealed that thin subfoveal choroidal thickness (p = 0.028), presence of subretinal drusenoid deposit (p = 0.005), type 2 or 3 NV (p = 0.023), and geographic atrophy in the fellow eye (p = 0.035) were significant risk factors for MA with foveal involvement. The number of injections showed no significant association with the progression or the foveal involvement in MA.

CONCLUSIONS

The progression of MA in patients with neovascular AMD undergoing anti-VEGF treatment differed significantly depending on the subtype of neovascularization. The risk of foveal involvement in MA was associated with the baseline factors or phenotype of neovascular AMD rather than with injection frequency of anti-VEGF.

Measuring the Contributions of Basal Laminar Deposit and Bruch's Membrane in Age-Related Macular Degeneration

Purpose

Basal laminar deposit (BLamD) is a consistent finding in age-related macular degeneration (AMD). We quantified BLamD thickness, appearance, and topography in eyes of aged donors with and without AMD and evaluated its relationship to other components of the retinal pigment epithelium-basal lamina/Bruch's membrane (RPE-BL-BrM) complex.

Methods

Donor eyes (n = 132) were classified as normal (n = 54), early to intermediate AMD (n = 24), geographic atrophy (GA; n = 13), and neovascular AMD (NV; n = 41). In high-resolution histology, we assessed RPE, BLamD, and BrM thicknesses and phenotypes at 3309 predefined locations in the central (foveal and perifovea) and superior (perifoveal) sections. Pre-mortem optical coherence tomography (OCT) imaging of a 90-year-old woman was compared to postmortem histopathology.

Results

In non-atrophic areas of AMD eyes, the RPE-BLamD is thick (normal = 13.7 µm, early-intermediate = 16.8 µm, GA = 17.4 µm, NV = 18.7 µm), because the BLamD is thick (normal = 0.3 µm, early-intermediate = 5.5 µm, GA = 4.1 µm, NV = 5.3 µm). RPE layer thickness is similar across these stages. Disease-associated variants of BLamD (thick, late, basal mounds) cluster subfoveally. A thick BLamD is visible on OCT as a hyporeflective split in the RPE-BL-BrM complex. BrM is thin (3.5 µm) in NV (normal = 4.2 µm, early to intermediate = 4.4 µm, and GA = 4.2 µm).

Conclusions

The RPE-BL-BrM complex is thick in AMD, driven by the accumulation and expansion of BLamD rather than expansion of either three-layer BrM, RPE-BL, or RPE. BLamD is clinically appreciable by OCT in some patients as a non-neovascular "split RPE-BL-BrM complex" or "double-layer sign." BLamD may contribute toward the formation and progression of high-risk drusen yet also exhibit protective properties.

Age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of legal blindness in the industrialized world. AMD is characterized by accumulation of extracellular deposits, namely drusen, along with progressive degeneration of photoreceptors and adjacent tissues. AMD is a multifactorial disease encompassing a complex interplay between ageing, environmental risk factors and genetic susceptibility. Chronic inflammation, lipid deposition, oxidative stress and impaired extracellular matrix maintenance are strongly implicated in AMD pathogenesis. However, the exact interactions of pathophysiological events that culminate in drusen formation and the associated degeneration processes remain to be elucidated. Despite tremendous advances in clinical care and in unravelling pathophysiological mechanisms, the unmet medical need related to AMD remains substantial. Although there have been major breakthroughs in the treatment of exudative AMD, no efficacious treatment is yet available to prevent progressive irreversible photoreceptor degeneration, which leads to central vision loss. Compelling progress in high-resolution retinal imaging has enabled refined phenotyping of AMD in vivo. These insights, in combination with clinicopathological and genetic correlations, have underscored the heterogeneity of AMD. Hence, our current understanding promotes the view that AMD represents a disease spectrum comprising distinct phenotypes with different mechanisms of pathogenesis. Hence, tailoring therapeutics to specific phenotypes and stages may, in the future, be the key to preventing irreversible vision loss.