Impact of Drusen Volume on Quantitative Fundus Autofluorescence in Early and Intermediate Age-Related Macular Degeneration

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Changes in drusen-associated autofluorescence over time observed by fluorescence lifetime imaging ophthalmoscopy in age-related macular degeneration

PURPOSE

To observe fundus autofluorescence (FAF) lifetimes and peak emission wavelength (PEW) of drusen with respect to the pathology of the overlying RPE in the follow-up of AMD-patients.

METHODS

Forty eyes of 38 patients (age: 75.1 ± 7.1 years) with intermediate AMD were included. FAF lifetimes and PEW were recorded by fluorescence lifetime imaging ophthalmoscopy (FLIO). Twenty-six eyes had a follow-up investigation between months 12 and 36, and 10 at months 37-72. AMD progression was retrieved from color fundus photography (CFP) and OCT. Drusen were classified with respect to changes in the overlying RPE into groups no, questionable or faint, and apparent hyperpigmentation based on CFP.

RESULTS

Among the 210 hyperautofluorescent drusen found at baseline, those with hyperpigmentation had longer lifetimes and shorter PEW than those without. Drusen without hyperpigmentation had shorter lifetimes and PEW than neighboring RPE (all p < 0.001) at baseline, but drusen lifetimes increased, and PEW shortened further over follow-up. Eyes, showing AMD progression, had significantly longer FAF lifetimes at baseline than non-progressing eyes: 282 ± 102 ps versus 245 ± 98 ps, p < 0.001 and 365 ± 44 ps vs. 336 ± 48 ps, p = 0.025 for short and long wavelength FLIO channel, respectively.

CONCLUSIONS

Depending on hyperpigmentation properties, drusen show lifetimes and PEW different from that of adjacent RPE which change over the natural history of AMD. This difference and change, however, might reflect progressive dysmorphia of the RPE rather than representing fluorescence of drusen material itself. Nevertheless, the observed FAF changes could make FLIO a useful tool for the early detection of AMD progression risk.

Quantitative Autofluorescence in Non-Neovascular Age Related Macular Degeneration

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

Impact of the Aging Lens and Posterior Capsular Opacification on Quantitative Autofluorescence Imaging in Age-Related Macular Degeneration

Purpose

The purpose of this study was to investigate quantitative autofluorescence (qAF8) in patients with and without early or intermediate age-related macular degeneration (AMD); to determine the impact of the aged crystalline lens and posterior capsular opacification (PCO).

Methods

In phakic and pseudophakic eyes ≥60 years, AMD status was determined by the Beckman system. PCO presence and severity was extracted from clinical records. qAF8 was calculated using custom FIJI plugins. Differences in qAF8, stratified by lens status, PCO severity, and AMD status, were analyzed using generalized estimating equations.

Results

In 210 eyes of 115 individuals (mean age = 75.7 ± 6.6 years), qAF8 was lower in intermediate AMD compared to early AMD (P = 0.05). qAF8 did not differ between phakic and pseudophakic eyes (P = 0.8909). In phakic (n = 83) and pseudophakic (n = 127) eyes considered separately, qAF8 did not differ by AMD status (P = 0.0936 and 0.3494, respectively). Qualitative review of qAF images in phakic eyes illustrated high variability. In pseudophakic eyes, qAF8 did not differ with PCO present versus absent (54.5% vs. 45.5%). Review of implanted intraocular lenses (IOLs) revealed that 43.9% were blue-filter IOLs.

Conclusions

qAF8 was not associated with AMD status, up to intermediate AMD, considering only pseudophakic eyes to avoid noisy images in phakic eyes. In pseudophakic eyes, qAF8 was not affected by PCO. Because blue-filter IOLs may reduce levels of exciting light for qAF8, future studies investigating qAF in eyes with different IOL types are needed.

Translational Relevance

To reduce variability in observational studies and clinical trials requiring qAF8, pseudophakic participants without blue-filter IOLs or advanced PCO should be preferentially enrolled.

Histologic Cell Shape Descriptors for the Retinal Pigment Epithelium in Age-Related Macular Degeneration: A Comparison to Unaffected Eyes

Purpose

Phenotype alterations of the retinal pigment epithelium (RPE) are a main characteristic of age-related macular degeneration (AMD). Individual RPE cell shape descriptors may help to delineate healthy from AMD-affected cells in early disease stages.

Methods

Twenty-two human RPE flatmounts (7 eyes with AMD [early, 3; geographic atrophy, 1; neovascular, 3); 15 unaffected eyes [8 aged ≤51 years; 7 aged >80 years)] were imaged at the fovea, perifovea, and near periphery (predefined sample locations) using a laser-scanning confocal fluorescence microscope. RPE cell boundaries were manually marked with computer assistance. For each cell, 11 shape descriptors were calculated and correlated with donor age, cell autofluorescence (AF) intensity, and retinal location. Statistical analysis was performed using an ensemble classifier based on logistic regression.

Results

In AMD, RPE was altered at all locations (most pronounced at the fovea), with area, solidity, and form factor being the most discriminatory descriptors. In the unaffected macula, aging had no significant effect on cell shape factors; however, with increasing distance to the fovea, area, solidity, and convexity increased while form factor decreased. Reduced AF in AMD was significantly associated with decreased roundness and solidity.

Conclusions

AMD results in an altered RPE with enlarged and deformed cells that could precede clinically visible lesions and thus serve as early biomarkers for AMD onset. Our data may also help guide the interpretation of RPE morphology in in vivo studies utilizing high-resolution single-cell imaging.

Translational Relevance

Our histologic RPE cell shape data have the ability to identify robust biomarkers for the early detection of AMD-affected cells, which also could serve as a basis for automated segmentation of RPE sheets.

Histology and Clinical Lifecycle of Acquired Vitelliform Lesion, a Pathway to Advanced Age-Related Macular Degeneration

PURPOSE

To evaluate hypotheses about the role of acquired vitelliform lesion (AVL) in age-related macular degeneration pathophysiology.

DESIGN

Laboratory histology study; retrospective, observational case series.

METHODS

Two donor eyes in a research archive with AVL and age-related macular degeneration were analyzed with light and electron microscopy for AVL content at locations matched to ex vivo B-scans. A retrospective, observational clinical cohort study of 42 eyes of 30 patients at 2 referral clinics determined the frequency of optical coherence tomography features stratified by AVL fate.

RESULTS

Histologic and clinical cases showed subretinal drusenoid deposit and drusen. Ultrastructural AVL components in 2 donor eyes included retinal pigment epithelium (RPE) organelles (3%-22% of volume), outer segments (2%-10%), lipid droplets (0.2%-12%), and a flocculent material (57%-59%). Of 48 AVLs (mean follow-up 46 ± 39 months), 50% collapsed to complete RPE and outer retinal atrophy, 38% were stable, 10% resorbed, and 2% developed neovascularization. The Early Treatment Diabetic Retinopathy Study grid central subfield contained 77% of AVLs. Hyperreflective foci, ellipsoid zone disruption, and hyperreflective thickening of the RPE-basal lamina-Bruch membrane band were common at maximum AVL expansion. Collapsing and noncollapsing AVLs had different growth rates (rapid vs slow, respectively).

CONCLUSIONS

AVL deposits contain unexpectedly low levels of RPE organelles and outer segments. Subfoveal predilection, reflectivity on optical coherence tomography, hyperautofluorescence, yellow color, and growth-regression phases suggest dysregulation of lipid transfer pathways specific to cone photoreceptors and supporting cells in formation of AVL deposit, analogous to drusen and subretinal drusenoid deposit. Prediction of AVL outcomes via growth rates should be confirmed in larger clinical studies.

Quantitative autofluorescence findings in patients undergoing hydroxychloroquine treatment

Background

Methods

Results

Conclusions

Autofluorescent Organelles Within the Retinal Pigment Epithelium in Human Donor Eyes With and Without Age-Related Macular Degeneration

Purpose

Human retinal pigment epithelium (RPE) cells contain lipofuscin, melanolipofuscin, and melanosome organelles that impact clinical autofluorescence (AF) imaging. Here, we quantified the effect of age-related macular degeneration (AMD) on granule count and histologic AF of RPE cell bodies.

Methods

Seven AMD-affected human RPE-Bruch's membrane flatmounts (early and intermediate = 3, late dry = 1, and neovascular = 3) were imaged at fovea, perifovea, and near periphery using structured illumination and confocal AF microscopy (excitation 488 nm) and compared to RPE-flatmounts with unremarkable macula (n = 7, >80 years). Subsequently, granules were marked with computer assistance, and classified by their AF properties. The AF/cell was calculated from confocal images. The total number of granules and AF/cell was analyzed implementing a mixed effect analysis of covariance (ANCOVA).

Results

A total of 152 AMD-affected RPE cells were analyzed (fovea = 22, perifovea = 60, and near-periphery = 70). AMD-affected RPE cells showed increased variability in size and a significantly increased granule load independent of the retinal location (fovea: P = 0.02, perifovea: P = 0.04, and near periphery: P < 0.01). The lipofuscin fraction of total organelles decreased and the melanolipofuscin fraction increased in AMD, at all locations (especially the fovea). AF was significantly lower in AMD-affected cells (fovea: <0.01, perifovea: <0.01, and near periphery: 0.02).

Conclusions

In AMD RPE, lipofuscin was proportionately lowest in the fovea, a location also known to be affected by accumulation of soft drusen and preservation of cone-mediated visual acuity. Enlarged RPE cell bodies displayed increased net granule count but diminished total AF. Future studies should also assess the impact on AF imaging of RPE apical processes containing melanosomes.

Spectral fundus autofluorescence peak emission wavelength in ageing and AMD

PURPOSE

To investigate the spectral characteristics of fundus autofluorescence (FAF) in AMD patients and controls.

METHODS

Fundus autofluorescence spectral characteristics was described by the peak emission wavelength (PEW) of the spectra. Peak emission wavelength (PEW) was derived from the ratio of FAF recordings in two spectral channels at 500-560 nm and 560-720 nm by fluorescence lifetime imaging ophthalmoscopy. The ratio of FAF intensity in both channels was related to PEW by a calibration procedure. Peak emission wavelength (PEW) measurements were done in 44 young (mean age: 24.0 ± 3.8 years) and 18 elderly (mean age: 67.5 ± 10.2 years) healthy subjects as well as 63 patients with AMD (mean age: 74.0 ± 7.3 years) in each pixel of a 30° imaging field. The values were averaged over the central area, the inner and the outer ring of the ETDRS grid.

RESULTS

There was no significant difference between PEW in young and elderly controls. However, PEW was significantly shorter in AMD patients (ETDRS grid centre: 571 ± 26 nm versus 599 ± 17 nm for elderly controls, inner ring: 596 ± 17 nm versus 611 ± 11 nm, outer ring: 602 ± 16 nm versus 614 ± 11 nm). After a mean follow-up time of 50.8 ± 10.8 months, the PEW in the patients decreased significantly by 9 ± 19 nm in the inner ring of the grid. Patients, showing progression to atrophic AMD in the follow up, had significantly (p ≤ 0.018) shorter PEW at baseline than non-progressing patients.

CONCLUSIONS

Peak emission wavelength (PEW) is related to AMD pathology and might be a diagnostic marker in AMD. Possibly, a short PEW can predict progression to retinal and/or pigment epithelium 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.

INVESTIGATING A GROWTH PREDICTION MODEL IN ADVANCED AGE-RELATED MACULAR DEGENERATION WITH SOLITARY GEOGRAPHIC ATROPHY USING QUANTITATIVE AUTOFLUORESCENCE

PURPOSE

To investigate geographic atrophy (GA) progression using quantitative autofluorescence (qAF) in eyes with solitary GA.

METHODS

Forty-three eyes of 26 patients (age 79.7 ± 7.2 years; 28 women; 16 pseudophakic) underwent spectral-domain optical coherence tomography and qAF imaging at baseline and after 12 months. The junctional zone (AJZ) and a nonaffected 300-µm-wide control area (AC) were delineated on spectral-domain optical coherence tomography scans and transferred to the qAF image. Linear mixed models were calculated to investigate the association between GA progression and qAF, age, and baseline GA area. Mixed model analyses of variance were used to investigate differences in qAF between areas.

RESULTS

Quantitative autofluorescence of the three inferior sections of both the AJZ (P = 0.028; P = 0.014 and P = 0.032) and the AC (P = 0.043; P = 0.02 and P = 0.028) were significantly associated with GA progression after 12 months. However, qAF measurements were not associated with GA progression in the overall model (P > 0.05). Mean qAF was significantly lower in the AJZ and growth area (AG12) than in the AC (both P ≤ 0.001).

CONCLUSION

The authors report a statistically significant association between GA growth area and qAF measurements at specific retinal locations and a significant difference in qAF between the GA border and unaffected areas outside the lesion. Quantitative autofluorescence measurements may be limitedly useful for predicting GA progression.

Influence of lens opacities and cataract severity on quantitative fundus autofluorescence as a secondary outcome of a randomized clinical trial

The aim of this study is to investigate the impact of age-related lens opacities and advanced cataract, quantified by LOCS III grading, on quantitative autofluorescence (qAF) measurements in patients before and after cataract surgery. Images from a randomized controlled trial evaluating the impact of femtosecond-laser assisted cataract surgery (FLACS) on retinal thickness were analyzed post-hoc. One-hundred and twenty eyes from 60 consecutive patients with age-related cataract were included and assessed with qAF and optical coherence tomography (OCT) before, 1, 3 and 6 weeks after cataract surgery (randomized 1:1 to FLACS or phacoemulsification). LOCS III grading was performed before surgery. Pre- to post-surgical qAF values, as well as the impact of LOCS III gradings, surgery technique, gender, axial length and age on post-surgery qAF values was investigated using generalized linear mixed models. For this analysis, 106 eyes from 53 patients were usable. No difference in qAF was found between FLACS and phacoemulsification (p > 0.05) and results were pooled for the total cohort. Mean pre-surgical qAF was 89.45 ± 44.9 qAF units, with a significant mean increase of 178.4–191.6% after surgery (p < 0.001). No significant difference was found between the three follow-up visits after surgery (p > 0.05). Higher LOCS III cortical opacity quantifications were associated with a significantly greater increase in qAF after surgery (estimate: 98.56, p = 0.006) and nuclear opacities showed a trend toward an increased change (estimate: 48.8, p = 0.095). Considerable interactions were identified between baseline qAF and cortical opacities, nuclear opacities and posterior subcapsular opacities, as well as nuclear opacities and cortical opacities (p = 0.012, p = 0.064 and p = 0.069, respectively). Quantitative autofluorescence signals are significantly reconstituted after cataract surgery and LOCS III gradings are well associated with post-surgical qAF values. Careful consideration of age-related lens opacities is vital for the correct interpretation of qAF, especially in retinal diseases affecting the elderly.

ClinicalTrials.gov Identifier: NCT03465124.

LONGITUDINAL CHANGES IN QUANTITATIVE AUTOFLUORESCENCE DURING PROGRESSION FROM INTERMEDIATE TO LATE AGE-RELATED MACULAR DEGENERATION

PURPOSE

To prospectively investigate the development of quantitative autofluorescence (qAF) during progression from intermediate to late age-related macular degeneration (AMD).

METHODS

Quantitative autofluorescence images from patients with intermediate AMD were acquired every three months with a Spectralis HRA + OCT (Heidelberg Engineering, Heidelberg, Germany) using a built-in autofluorescence reference. The association between changes in longitudinal qAF and progression toward late AMD was assessed using Cox regression models with time-dependent covariates.

RESULTS

One hundred and twenty-one eyes of 71 patients were included, and 653 qAF images were acquired. Twenty-one eyes of 17 patients converted to late AMD (median follow-up: 21 months; 12 eyes: atrophic AMD; nine eyes: neovascular AMD). The converting patients' mean age was 74.6 ± 4.4 years. Eleven eyes in the converting group (52.4%) were pseudophakic. The presence of an intraocular lens did not affect the qAF regression slopes (P > 0.05). The median change for atrophic AMD was -2.34 qAF units/3 months and 0.78 qAF units/3 months for neovascular AMD. A stronger decline in qAF was significantly associated with an increased risk of developing atrophic AMD (hazard ratio = 1.022, P < 0.001). This association, however, was not present in the group progressing toward neovascular AMD (hazard ratio = 1.001, P = 0.875).

CONCLUSION

The qAF signal declines with progression to atrophy, contrary to developing neovascularization. Quantitative autofluorescence may allow identification of patients at risk of progressing to late AMD and benefits individualized patient care in intermediate AMD.

Quantitative autofluorescence: Review of Current Technical Aspects and Applications in Chorioretinal Disease

Purpose: In this review we discuss the broad clinical application of qAF and provide a descriptive summary of the phenotypic findings of different chorioretinal pathologies.Background: Quantitative Fundus autofluorescence (qAF) is a novel developing technology that can aid in diagnosis and longitudinal disease monitoring by measuring and comparing autofluorescence intensities. Fundus autofluorescence (FAF) is a noninvasive imaging method that creates a density map of the fluorophores of the ocular fundus and provides both functional and topographic anatomic information about retinal cells. Fluorophores are molecules that have the ability to temporarily absorb irradiated light, and emit a small amount of light of a different wavelength. Different endogenous fluorophores can be found in the ocular fundus. Changes in accumulation of retinal fluorophores usually indicate retinal pathology and create characteristic patterns of hyper-autofluorescence and hypo-autofluorescence that help establish a diagnosis.Conclusion: qAF allows a safe non-invasive visualization of the retina, enables a standard for AF intensities comparison and aids to the understanding of the genotype-phenotype correlations.

CORRELATION STUDY BETWEEN DRUSEN MORPHOLOGY AND FUNDUS AUTOFLUORESCENCE

PURPOSE

To correlate drusen morphology and outer retinal status with autofluorescence (AF) imaging in patients with intermediate age-related macular degeneration.

METHODS

Drusen type and morphology were analyzed using color fundus photography and spectral-domain optic coherence tomography, whereas fundus AF was used for drusen AF evaluation. Additional structural changes on spectral-domain optic coherence tomography, such as disruption of external limiting membrane, ellipsoid zone, and retinal pigment epithelium/Bruch membrane complex, as well as the presence of choroidal hypertransmission at correspondent locations were also evaluated and correlated with fundus AF findings. Spearman's correlation coefficient was used to analyze the correlation between spectral-domain optic coherence tomography morphological characteristics of drusen and AF appearance of the corresponding drusen. Strength of correlation was calculated (r), and a P value < 0.05 was considered statistically significant.

RESULTS

Two hundred and twenty-eight drusen from 53 eyes of 53 patients were analyzed, 130 soft drusen (57.02%) and 98 cuticular drusen (42.98%). Sixty percent of the drusen were isoautofluorescent (n = 136), 35% hyperautofluorescent (n = 80), and 5% hypoautofluorescent (n = 12). We found positive correlation between drusen AF and hyperreflective foci (r = 0.4). Outer retinal layers morphology (external limiting membrane and ellipsoid zone status and hypertransmission) also correlates with autofluorescent findings (r = 0.3).

CONCLUSION

Multimodal imaging reveals a broad spectrum of ultrastructural changes, which may reflect different stages in the evolution of drusen. Our results suggest that drusen morphological characteristics and autofluorescent findings are correlated but other factors or cofactors may be involved. The described correlations will help us understand new progression biomarkers of nonexudative age-related macular degeneration.

Quantitative Fundus Autofluorescence in Systemic Chloroquine/Hydroxychloroquine Therapy

Purpose

To investigate the effect of systemic chloroquine/hydroxychloroquine (CQ/HCQ) on outer retinal health using quantitative fundus autofluorescence (QAF) imaging.

Methods

For this prospective, cross-sectional study, 44 CQ/HCQ patients and 25 age-matched controls underwent multimodal retinal imaging including QAF (488 nm) and spectral-domain optical coherence tomography (SD-OCT) in addition to the recommended CQ/HCQ screening procedures. Custom written FIJI plugins enabled detailed QAF analysis and correlation with retinal thickness and comparison to the healthy controls.

Results

Out of 44 patients, 29 (mean age 43.5 ± 12.2, range 22–59 years) exposed to CQ/HCQ (mean cumulative dose 724.2 ± 610.4 g, median 608.0 g, range 18.6–2171.0 g) met eligibility criteria. Four of these 29 patients had bull's-eye maculopathy (BEM). Mean QAF values were significantly higher in CQ/HCQ patients than in healthy controls. QAF increase started early after treatment onset, remained high even years after treatment cessation, and was not accompanied by pathologies in the other screening methods, including retinal thicknesses (except in BEM patients).

Conclusions

QAF might be a useful tool in retinal imaging and in verifying systemic CQ/HCQ intake. The early onset and preserved high levels of QAF parallel findings of CQ deposition in the retina in animal models. Whether QAF can be used as a screening tool to detect early CQ/HCQ related maculopathy is the subject of long-term ongoing studies.

Translation Relevance

Experimental QAF imaging in systemic CQ/HCQ therapy monitoring might be a useful tool to indicate the drug or its metabolites and to detect metabolic retinal changes.

Quantitative Fundus Autofluorescence: Advanced Analysis Tools

Purpose

To use multimodal retinal images (including quantitative fundus autofluorescence [QAF]) for spectral-domain optical coherence tomography (SD-OCT)-based image registration and alignment. For each age decade of healthy adults, normative fine-grained QAF retinal maps are generated and advanced methods for QAF image analysis are applied.

Methods

Multimodal retinal images were obtained from 103 healthy subjects (age 19–77 years; unremarkable retina/macula, age-appropriate clear optic media). Custom written FIJI plugins enabled: (1) determination of the fovea in SD-OCT and the edge of the optic disc in infrared (IR) images; (2) alignment and superimposition of multimodal retinal images based on foveal and optic disc position; (3) plotting of normative QAF retinal maps for each decade; and (4) comparison of individual retinas with normative retinas of different decades using newly introduced analysis patterns (QAF97, freehand tool).

Results

SD-OCT based image registration enables easy image registration, alignment, and analysis of different modalities (QAF, IR, and SD-OCT here reported). In QAF, intensities significantly increase with age with two major inclines between the third/fourth and seventh/eighth decades. With aging, the parafoveal area of maximum QAF intensity slightly shifts from temporal-superior to temporal. Compared with standard QAF analysis, refined QAF analysis patterns reveal a more detailed analysis of QAF, especially in the diseased retina.

Conclusions

Age-related QAF normative retinal maps can be used to directly compare and classify individual's QAF intensities. Advanced QAF analysis tools will further help to interpret autofluorescence changes in normal aging and in the diseased retina in a multimodal imaging setting.

Translational Relevance

Advanced methods for QAF analysis link basic findings with clinical observations in normal aging and in the diseased macula.

Translational Retinal Imaging

The diagnosis and treatment of medical retinal disease is now inseparable from retinal imaging in all its multimodal incarnations. The purpose of this article is to present a selection of very different retinal imaging techniques that are truly translational, in the sense that they are not only new, but can guide us to new understandings of disease processes or interventions that are not accessible by present methods. Quantitative autofluorescence imaging, now available for clinical investigation, has already fundamentally changed our understanding of the role of lipofuscin in age-related macular degeneration. Hyperspectral autofluorescence imaging is bench science poised not only to unravel the molecular basis of retinal pigment epithelium fluorescence, but also to be translated into a clinical camera for earliest detection of age-related macular degeneration. The ophthalmic endoscope for vitreous surgery is a radically new retinal imaging system that enables surgical approaches heretofore impossible while it captures subretinal images of living tissue. Remote retinal imaging coupled with deep learning artificial intelligence will transform the very fabric of future medical care.

Genetic LAMP2 deficiency accelerates the age-associated formation of basal laminar deposits in the retina

Extracellular tissue debris accumulates with aging and in the most prevalent central-vision-threatening eye disorder, age-related macular degeneration (AMD). In this work, we discovered that lysosome-associated membrane protein-2 (LAMP2), a glycoprotein that plays a critical role in lysosomal biogenesis and maturation of autophagosomes/phagosomes, is preferentially expressed in the outermost, neuroepithelial layer of the retina, the retinal pigment epithelium (RPE), and contributes to the prevention of ultrastructural changes in extracellular basolaminar deposits including lipids and apolipoproteins. LAMP2 thus appears to play an important role in RPE biology, and its apparent decrease with aging and in AMD specimens suggests that its deficiency may accelerate the basolaminar deposit formation and RPE dysfunction seen in these conditions.

The early stages of age-related macular degeneration (AMD) are characterized by the accumulation of basal laminar deposits (BLamDs). The mechanism for BLamDs accumulating between the retinal pigment epithelium (RPE) and its basal lamina remains elusive. Here we examined the role in AMD of lysosome-associated membrane protein-2 (LAMP2), a glycoprotein that plays a critical role in lysosomal biogenesis and maturation of autophagosomes/phagosomes. LAMP2 was preferentially expressed by RPE cells, and its expression declined with age. Deletion of the Lamp2 gene in mice resulted in age-dependent autofluorescence abnormalities of the fundus, thickening of Bruch’s membrane, and the formation of BLamDs, resembling histopathological changes occurring in AMD. Moreover, LAMP2-deficient mice developed molecular signatures similar to those found in human AMD—namely, the accumulation of APOE, APOA1, clusterin, and vitronectin—adjacent to BLamDs. In contrast, collagen 4, laminin, and fibronectin, which are extracellular matrix proteins constituting RPE basal lamina and Bruch’s membrane were reduced in Lamp2 knockout (KO) mice. Mechanistically, retarded phagocytic degradation of photoreceptor outer segments compromised lysosomal degradation and increased exocytosis in LAMP2-deficient RPE cells. The accumulation of BLamDs observed in LAMP2-deficient mice was eventually followed by loss of the RPE and photoreceptors. Finally, we observed loss of LAMP2 expression along with ultramicroscopic features of abnormal phagocytosis and exocytosis in eyes from AMD patients but not from control individuals. Taken together, these results indicate an important role for LAMP2 in RPE function in health and disease, suggesting that LAMP2 reduction may contribute to the formation of BLamDs in AMD.