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.

INFLAMMATORY CELL ACTIVITY IN TREATED NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: A Histologic Case Study.

BACKGROUND: Imaging indicators of macular neovascularization risk can help determine patient eligibility for new treatments for geographic atrophy secondary to age-related macular degeneration. Because type 1 macular neovascularization includes inflammation, we assessed by histology the distribution of cells with inflammatory potential in two fellow eyes with age-related macular degeneration. METHODS: Two eyes of a White woman in her 90's with type 3 macular neovascularization treated with antivascular endothelial growth factor were prepared for high-resolution histology. Eye-tracked spectral domain optical coherence tomography applied to the preserved donor eyes linked in vivo imaging to histology. Cells were enumerated in the intraretinal, subretinal, and subretinal retinal pigment epithelium (RPE)-basal lamina compartments on 199 glass slides. Cells with numerous organelles were considered to RPE-derived; cells with sparse RPE organelles were considered non-RPE phagocytes. RESULTS: Both eyes had soft drusen and abundant subretinal drusenoid deposit. In the retina and subretinal space, RPE-derived cells, including hyperreflective foci, were common (n = 125 and 73, respectively). Non-RPE phagocytes were infrequent (n = 5 in both). Over drusen, RPE morphology transitioned smoothly from the age-normal layer toward the top, suggesting transdifferentiation. The sub-RPE-basal lamina space had RPE-derived cells (n = 87) and non-RPE phagocytes (n = 49), including macrophages and giant cells. CONCLUSION: Numerous sub-RPE-basal lamina cells of several types are consistent with the documented presence of proinflammatory lipids in drusen and aged Bruch's membrane. The relatively compartmentalized abundance of infiltrating cells suggests that drusen contents are more inflammatory than subretinal drusenoid deposit, perhaps reflecting their environments. Ectopic RPE occurs frequently. Some manifest as hyperreflective foci. More cells may be visible as optical coherence tomography technologies evolve.

Untargeted Lipidomic Profiling of Aged Human Retina With and Without Age-Related Macular Degeneration (AMD).

The molecular characterization of extracellular deposits is crucial to understanding the clinical progression of AMD. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis is a powerful analytical discovery tool capable of identifying lipids in an untargeted manner. NanoLC-MS/MS is an analytical tool capable of identifying lipids with high sensitivity and minimum sample usage. Hence, the purpose of this study was to compare retina lipid identification from RPE-choroid samples using high flow LC-MS/MS and nanoLC-MS/MS. Manually dissected paraformaldehyde-fixed human donor tissues sections were used for LC-MS/MS and nanoLC-MS/MS analysis. Lipids were extracted with MeOH/MTBE/CHCl3 (MMC) and were analyzed by LC-MS/MS and nanoLC-MS/MS using negative and positive ionization modes. Untargeted lipidomics using LC-MS/MS identified 215 lipids from 4 lipid classes and 15 subclasses. We observed a 78% increase in lipid identifications using nanoLC-MS/MS with lipid numbers totaling 384. The nanoLC-MS/MS method is expected to provide extensive lipid identifications from small retina samples, e.g., from drusen and drusenoid deposits in aged and AMD eyes, and could help elucidate how lipids are involved in extracellular deposit formation in AMD.

High-Resolution Imaging Mass Spectrometry of Human Donor Eye: Photoreceptors Cells and Basal Laminar Deposit of Age-Related Macular Degeneration.

Pathologies of the retina are clinically visualized in vivo with OCT and ex vivo with immunohistochemistry. Although both techniques provide valuable information on prognosis and disease state, a comprehensive method for fully elucidating molecular constituents present in locations of interest is desirable. The purpose of this work was to use multimodal imaging technologies to localize the vast number of molecular species observed with matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) in aged and diseased retinal tissues. Herein, MALDI IMS was utilized to observe molecular species that reside in photoreceptor cells and also a basal laminar deposit from two human donor eyes. The molecular species observed to accumulate in these discrete regions can be further identified and studied to attempt to gain a greater understanding of biological processes occurring in debilitating eye diseases such as age-related macular degeneration (AMD).

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.

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

PURPOSE: Type 1 macular neovascularization (MNV) secondary to age-related macular degeneration (AMD) may sustain hypoxic and micronutrient-insufficient outer retinal cells compensatorily. We explored this hypothesis via histologic analysis of an eye with a shallow irregular retinal pigment epithelial elevation (SIRE) on OCT and good vision. DESIGN: Case study and clinicopathologic correlation. PARTICIPANT: A white woman with untreated nonexudative neovascular AMD and 20/30 visual acuity (left eye) and neovascular AMD (right eye), with 9 years' multimodal imaging before dying at 90 years of age. METHODS: The left eye was preserved 6.25 hours after death and prepared for submicrometer epoxy resin sections and transmission electron microscopy aligned to clinical OCT B-scans. Inside and outside the MNV area, layer thicknesses, phenotypes, and vascular density of native choriocapillaris and neovessels were measured. Lengths of choriocapillaries and intervening gaps in the index eye and in early AMD eyes and healthy eyes with similar age (n = 19 each) from the Project MACULA (Maculopathy Unveiled by Laminar Analysis) online histopathologic resource (http://projectmacula.cis.uab.edu/) were measured with custom software (Caps and Gaps). MAIN OUTCOME MEASURES: Descriptive features, vascular density, histologic and OCT layer thicknesses, and distribution of choriocapillaries and intervening gaps. RESULTS: The SIRE correlated to a type 1 MNV that expanded slowly without evidence of exudation and with numerous choroidal vessels traversing Bruch's membrane defects, some visible on OCT. Tissue layers in and adjacent to the MNV area showed continuous RPE and characteristic AMD deposits. Capillary-like neovessels with fenestrations and caveolae resembling native choriocapillaris lined the retinal pigment epithelium (RPE) with a vascular density comparable with surrounding non-MNV areas. Relative to early AMD and healthy aged eyes, the index eye showed similar capillary lengths but larger gaps between vessels, indicating dropout. Outer nuclear layer thickness was preserved and showed less photoreceptor degeneration over areas of relative choriocapillaris health, including the type 1 MNV. CONCLUSIONS: Eyes with nonexudative type 1 MNV in AMD may progress to exudation, yet this stable MNV complex supported outer retinal structure for 9 years. Distinguishing features were numerous connecting vessels, high density of neovessels, continuous RPE, and slow growth. Maintaining beneficial type 1 MNV may be a therapeutic strategy.

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

PURPOSE: To clarify the role of subretinal drusenoid deposits (SDD; pseudodrusen) in the progression of age-related macular degeneration through high-resolution histology. METHODS: In 33 eyes of 32 donors (early age-related macular degeneration, n = 15; geographic atrophy, n = 9; neovascular age-related macular degeneration, n = 7; unremarkable, n = 2), and 2 eyes of 2 donors with in vivo multimodal imaging including optical coherence tomography, examples of SDD contacting photoreceptors were assessed. RESULTS: Subretinal drusenoid deposits were granular extracellular deposits at the apical retinal pigment epithelium (RPE); the smallest were 4-µm wide. Outer segment (OS) fragments and RPE organelles appeared in some larger deposits. A continuum of photoreceptor degeneration included OS disruption, intrusion into inner segments, and disturbance of neurosensory retina. In a transition to outer retinal atrophy, SDD appeared to shrink, OS disappeared, inner segment shortened, and the outer nuclear layer thinned and became gliotic. Stage 1 SDD on optical coherence tomography correlated with displaced OS. Confluent and disintegrating Stage 2 to 3 SDD on optical coherence tomography and dot pseudodrusen by color fundus photography correlated with confluent deposits and ectopic RPE. CONCLUSION: Subretinal drusenoid deposits may start at the RPE as granular, extracellular deposits. Photoreceptor OS, RPE organelles, and cell bodies may appear in some advanced deposits. A progression to atrophy associated with deposit diminution was confirmed. Findings support a biogenesis hypothesis of outer retinal lipid cycling.

ABUNDANCE AND MULTIMODAL VISIBILITY OF SOFT DRUSEN IN EARLY AGE-RELATED MACULAR DEGENERATION: A Clinicopathologic Correlation.

PURPOSE: To determine the abundance and multimodal visibility of drusen and basal linear deposit (BLinD) in early age-related macular degeneration. METHODS: A 69-year-old white man was imaged by color fundus photography and red free photography, fundus autofluorescence, and optical coherence tomography. From en face images, we determined the drusen field, drusen area, and equivalent diameters of individual drusen. From high-resolution light-microscopic histology (6 months after the last clinic visit), we determined the area of drusen, BLinD, and pre-BLinD in a subretinal pigment epithelium-basal lamina lipid field. RESULTS: In right and left eyes, respectively, BLinD covered 40% and 46% of the lipid field, versus 21% and 14% covered by drusen. The lipid field was covered 60% to 61% by Drusen + BLinD and 65% to 72% by BLinD + pre-BLinD. In the left eye, the drusen area on color fundus photography (0.18 mm) and red free (0.28 mm) was smaller than the drusen area on histology (1.16 mm). Among drusen confirmed by optical coherence tomography, 55.1% and 56.6% were observed on red free and fundus autofluorescence, respectively. CONCLUSION: Basal linear deposit covered 1.9 and 3.4-fold more fundus area than soft drusen, silently increasing progression risk. Improved visualization of BLinD and readouts of the retinal pigment epithelium health over lipid will assist population surveillance, early detection, and trial outcome measures.

CLINICOPATHOLOGIC CORRELATION OF GEOGRAPHIC ATROPHY SECONDARY TO AGE-RELATED MACULAR DEGENERATION.

PURPOSE: In an eye with geographic atrophy (GA) secondary to age-related macular degeneration, we correlated ex vivo histologic features with findings recorded in vivo using optical coherence tomography (OCT), near-infrared reflectance imaging, and fundus autofluorescence. METHODS: In the left eye of an 86-year-old white woman, in vivo near-infrared reflectance and eye-tracked OCT B-scans at each of 6 clinic visits and a baseline fundus autofluorescence image were correlated with high-resolution histologic images of the preserved donor eye. RESULTS: Clinical imaging showed a small parafoveal multilobular area of GA, subfoveal soft drusen, refractile drusen, hyperreflective lines near the Bruch membrane, subretinal drusenoid deposit (reticular pseudodrusen), and absence of hyperautofluorescent foci at the GA margin. By histology, soft drusen end-stages included avascular fibrosis with highly reflective cholesterol crystals. These accounted for hyperreflective lines near the Bruch membrane in OCT and plaques in near-infrared reflectance imaging. Subretinal drusenoid deposit was thick, continuous, extracellular, extensive outside the fovea, and associated with distinctive retinal pigment epithelium dysmorphia and photoreceptor degeneration. A hyporeflective wedge corresponded to ordered Henle fibers without cellular infiltration. The external limiting membrane descent, which delimits GA, was best visualized in high-quality OCT B-scans. Retinal pigment epithelium and photoreceptor changes at the external limiting membrane descent were consistent with our recent histologic survey of donor eyes. CONCLUSION: This case informs on the extent, topography, and lifecycle of extracellular deposits. High-quality OCT scans are required to reveal all tissue features relevant to age-related macular degeneration progression to GA, especially the external limiting membrane descent. Histologically validated signatures of structural OCT B-scans can serve as references for other imaging modalities.

Clinicopathologic Correlation of Anti-Vascular Endothelial Growth Factor-Treated Type 3 Neovascularization in Age-Related Macular Degeneration.

PURPOSE: To correlate histologic results with previously recorded multimodal imaging results from a patient with type 3 neovascularization secondary to age-related macular degeneration (AMD). DESIGN: Case study, clinical imaging, laboratory imaging, and eye-tracked clinicopathologic correlation. PARTICIPANT: An 86-year-old white woman with type 3 neovascularization secondary to AMD treated with 6 intravitreal injections of bevacizumab. METHODS: Multimodal retinal imaging at each clinic visit was correlated with ex vivo and high-resolution histologic images of the preserved donor eye. Clinical imaging included serial near-infrared reflectance and eye-tracked spectral-domain OCT. Eye tracking, applied to the donor eye, enabled identification of histologic features corresponding to clinical OCT signatures. MAIN OUTCOME MEASURES: Histologic correlates for clinical OCT signatures were sought, including reflectivity of the vascular complex, intraretinal hyperreflective foci and intraretinal cellularity, analysis of the topography of pathologic features, and evaluation of the sub-retinal pigment epithelium (RPE) plus basal lamina (BL) space. RESULTS: Clinical imaging showed a deep neovascular lesion in close relationship with a mixed serous and drusenoid pigment epithelium detachment (PED), characteristic of type 3 neovascularization. Antiangiogenic therapy achieved a complete resolution of exudation. The PED progressively flattened with each treatment, leaving a persistent triangular hyperreflectivity in the outer retina. This persistent deep lesion histologically correlated with a vascular complex implanted into sub-RPE basal laminar deposit. No connection between the choriocapillaris and the sub-RPE plus BL space was observed. Both RPE-derived and lipid-filled cells were correlated with clinical intraretinal hyperreflective foci. The sub-RPE plus BL space contained macrophages, lymphocytes, Müller cell processes, and subducted RPE. CONCLUSIONS: Clinicopathologic correlation of type 3 neovascularization showed vascular elements of retinal origin accompanied by collagenous material and Müller cell processes implanting into thick sub-RPE basal laminar deposit, which may simulate the appearance of chorioretinal anastomosis. Surrounding RPE-derived and lipid-filled cells thought to be microglia correlated with clinical intraretinal hyperreflective foci.

Choroidal and Sub-Retinal Pigment Epithelium Caverns: Multimodal Imaging and Correspondence with Friedman Lipid Globules.

PURPOSE: To survey Friedman lipid globules by high-resolution histologic examination and to compare with multimodal imaging of hyporeflective caverns in eyes with geographic atrophy (GA) secondary to age-related macular (AMD) and other retinal diseases. DESIGN: Histologic survey of donor eyes with and without AMD. Clinical case series with multimodal imaging analysis. PARTICIPANTS: Donor eyes (n = 139; 26 with early AMD, 13 with GA, 40 with nAMD, 52 with a healthy macula, and 8 with other or unknown characteristics) and 41 eyes of 28 participants with GA (n = 16), nAMD (n = 8), Stargardt disease (n = 4), cone dystrophy (n = 2), pachychoroid spectrum (n = 6), choroidal hemangioma (n = 1), and healthy eyes (n = 4). METHODS: Donor eyes were prepared for macula-wide epoxy resin sections through the foveal and perifoveal area. In patients, caverns were identified as nonreflective spaces on OCT images. Multimodal imaging included color and red-free fundus photography; fundus autofluorescence; fluorescein and, indocyanine green angiography; OCT angiography; near-infrared reflectance; and confocal multispectral (MultiColor [Spectralis, Heidelberg Engineering, Germany]) imaging. MAIN OUTCOME MEASURES: Presence and morphologic features of globules, and presence and appearance of caverns on multimodal imaging. RESULTS: Globules were found primarily in the inner choroidal stroma (91.0%), but also localized to the sclera (4.9%) and neovascular membranes (2.1%). Mean diameters of solitary and multilobular globules were 58.9±37.8 µm and 65.4±27.9 µm, respectively. Globules showed morphologic signs of dynamism including pitting, dispersion, disintegration, and crystal formation. Evidence for inflammation in the surrounding tissue was absent. En face OCT rendered sharply delimited hyporeflective areas as large as choroidal vessels, frequently grouped around choroid vessels or in the neovascular tissue. Cross-sectional OCT revealed a characteristic posterior hypertransmission. OCT angiography showed absence of flow signal within caverns. CONCLUSIONS: Based on prior literature documenting OCT signatures of tissue lipid in atheroma and nAMD, we speculate that caverns are lipid rich. Globules, with similar sizes and tissue locations in AMD and healthy persons, are candidates for histologic correlates of caverns. The role of globules in chorioretinal physiologic features, perhaps as a lipid depot for photoreceptor metabolism, is approachable through clinical imaging.

Visualizing melanosomes, lipofuscin, and melanolipofuscin in human retinal pigment epithelium using serial block face scanning electron microscopy.

To assess serial section block-face scanning electron microscopy (SBFSEM) for retinal pigment epithelium (RPE) ultrastructure, we determined the number and distribution within RPE cell bodies of melanosomes (M), lipofuscin (L), and melanolipofuscin (ML). Eyes of 4 Caucasian donors (16M, 32F, 76F, 84M) with unremarkable maculas were sectioned and imaged using an SEM fitted with an in-chamber automated ultramicrotome. Aligned image stacks were generated by alternately imaging an epoxy resin block face using backscattered electrons, then removing a 125 nm-thick layer. Series of 249-499 sections containing 5-24 nuclei were examined per eye. Trained readers manually assigned boundaries of individual cells and x,y,z locations of M, L, and ML. A Density Recovery Profile was computed in three dimensions for M, L, and ML. The number of granules per RPE cell body in 16M, 32F, 76F, and 84M eyes, respectively, was 465 ± 127 (mean ± SD), 305 ± 92, 79 ± 40, and 333 ± 134 for L; 13 ± 9; 6 ± 7, 131 ± 55, and 184 ± 66 for ML; and 29 ± 19, 24 ± 12, 12 ± 7, and 7 ± 3 for M. Granule types were spatially organized, with M near apical processes. The effective radius, a sphere of decreased probability for granule occurrence, was 1 µm for L, ML, and M combined. In conclusion, SBFEM reveals that adult human RPE has hundreds of L, LF, and M and that granule spacing is regulated by granule size alone. When obtained for a larger sample, this information will enable hypothesis testing about organelle turnover and regulation in health, aging, and disease, and elucidate how RPE-specific signals are generated in clinical optical coherence tomography and autofluorescence imaging.

Histologic and Optical Coherence Tomographic Correlates in Drusenoid Pigment Epithelium Detachment in Age-Related Macular Degeneration.

PURPOSE: Drusenoid pigment epithelium detachment (DPED) is a known precursor to geographic atrophy in age-related macular degeneration (AMD). We sought histologic correlates for spectral-domain (SD) optical coherence tomography (OCT) signatures in DPED and determined the frequency and origin of these OCT signatures in a clinical cohort of DPED eyes. DESIGN: Laboratory imaging and histologic comparison, and retrospective, observational cohort study. PARTICIPANTS: Four donor eyes with histopathologic diagnosis of AMD (2 with nonneovascular DPED and 2 with neovascular pigment epithelium detachment [PED]) and 49 eyes of 33 clinic patients with nonneovascular DPED more than 2 mm in diameter. METHODS: Donor eyes underwent multimodal ex vivo imaging, including SD OCT, then processing for high-resolution histologic analysis. All clinic patients underwent SD OCT, near-infrared reflectance, and color photography. MAIN OUTCOME MEASURES: Histologic correlates for SD OCT signatures in DPED, estimate of coverage by different retinal pigment epithelium (RPE) phenotypes in the DPED surface; frequency and origin of histologically verified SD OCT signatures in a clinical cohort of DPED eyes, and comparisons of histologic features between neovascular PED and DPED resulting from AMD. RESULTS: Intraretinal and subretinal hyperreflective foci as seen on SD OCT correlated to RPE cells on histologic examination. Hypertransmission of light below the RPE-basal lamina band correlated with dissociated RPE. Subretinal hyperreflective material resulting from acquired vitelliform lesions corresponded to regions of apically expelled RPE organelles. In the clinical cohort, all histologically verified reflectivity signatures were visible and quantifiable. The appearance of intraretinal hyperreflective foci was preceded by thickening of the RPE-basal lamina band. Compared with PEDs associated with neovascular AMD, DPEDs had different crystallization patterns, no lipid-filled cells, and thinner basal laminar deposits. CONCLUSIONS: Multiple RPE fates in AMD, including intraretinal cells that are highly prognostic for progression, can be followed and quantified reliably using eye-tracked serial SD OCT. This information may be particularly useful for obtaining an accurate timeline of incipient geographic atrophy in clinic populations and for quantifying anatomic end points and response to therapy in AMD clinical trials.

Comprehensive analysis of gene expression in human retina and supporting tissues.

Understanding the influence of gene expression on the molecular mechanisms underpinning human phenotypic diversity is fundamental to being able to predict health outcomes and treat disease. We have carried out whole transcriptome expression analysis on a series of eight normal human postmortem eyes by RNA sequencing. Here we present data showing that ∼80% of the transcriptome is expressed in the posterior layers of the eye and that there is significant differential expression not only between the layers of the posterior part of the eye but also between locations of a tissue layer. These differences in expression also extend to alternative splicing and splicing factors. Differentially expressed genes are enriched for genes associated with psychiatric, immune and cardiovascular disorders. Enrichment categories for gene ontology included ion transport, synaptic transmission and visual and sensory perception. Lastly, allele-specific expression was found to be significant for CFH, C3 and CFB, which are known risk genes for age-related macular degeneration. These expression differences should be useful in determining the underlying biology of associations with common diseases of the human retina, retinal pigment epithelium and choroid and in guiding the analysis of the genomic regions involved in the control of normal gene expression.

VISUALIZING RETINAL PIGMENT EPITHELIUM PHENOTYPES IN THE TRANSITION TO GEOGRAPHIC ATROPHY IN AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To inform the interpretation of clinical optical coherence tomography and fundus autofluorescence imaging in geographic atrophy (GA) of age-related macular degeneration by determining the distribution of retinal pigment epithelium (RPE) phenotypes in the transition from health to atrophy in donor eyes. METHODS: In RPE-Bruch membrane flat mounts of two GA eyes, the terminations of organized RPE cytoskeleton and autofluorescent material were compared. In high-resolution histological sections of 13 GA eyes, RPE phenotypes were assessed at ±500 and ±100 µm from the descent of the external limiting membrane (ELM) toward Bruch membrane. The ELM descent was defined as curved, reflected, or oblique in shape. Thicknesses of RPE, basal laminar deposit (BLamD), and RPE plus BLamD were measured. RESULTS: A border of atrophy that can be precisely delimited is the ELM descent, as opposed to the termination of the RPE layer itself, because of dissociated RPE in the atrophic area. Approaching the ELM descent, the percentage of abnormal RPE morphologies increases, the percentage of age-normal cells decreases, overall RPE thickens, and BLamD does not thin. The combination of RPE plus BLamD is 19.7% thicker at -100 µm from the ELM descent than that at -500 µm (23.1 ± 10.7 µm vs. 19.3 ± 8.2 µm; P = 0.05). CONCLUSION: The distribution of RPE phenotypes at the GA transition supports the idea that these morphologies represent defined stages of a degeneration sequence. The idea that RPE dysmorphia including rounding and stacking helps explain variable autofluorescence patterns in GA is supported. The ELM descent and RPE plus BLamD thickness profile may have utility as spectral domain optical coherence tomography metrics in clinical trials.

VISUALIZING RETINAL PIGMENT EPITHELIUM PHENOTYPES IN THE TRANSITION TO ATROPHY IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To enable future studies of retinal pigment epithelium (RPE) fate in the macular atrophy occurring in eyes with neovascular age-related macular degeneration (nvAMD), the authors determined how RPE morphology changes across the transition from health to atrophy in donor eyes with nvAMD. METHOD: In RPE-Bruch membrane flat mounts of 5 nvAMD eyes, the terminations of organized RPE cytoskeleton and autofluorescent material were compared. In high-resolution histologic sections of 27 nvAMD eyes, RPE phenotypes were assessed at ±500 µm and ±100 µm from the descent of the external limiting membrane (ELM) toward the Bruch membrane. Thicknesses of RPE, basal laminar deposit (BLamD), and RPE + BLamD were determined. Shapes of the ELM descent were recorded. RESULTS: Approaching the ELM descent, the percentage of different RPE phenotypes and the thickness of RPE, BLamD, and RPE + BLamD each stayed roughly constant. Compared with a separately described cohort of eyes with geographic atrophy, eyes with nvAMD were more likely to have RPE dysmorphia that did not worsen toward the atrophy border, thinner BLamD overall (3.25 ± 3.46 µm vs. 7.99 ± 7.49 µm for geographic atrophy), and a higher proportion of oblique ELM descents (47.9 vs. 31.9%). CONCLUSION: The distribution of RPE phenotypes at the transition to macular atrophy in eyes with nvAMD differs from that in primary geographic atrophy, likely reflecting greater photoreceptor loss and the effects of exudation in nvAMD. This distribution, the shape of ELM descents, and thickness profiles may be useful metrics in clinical studies of macular atrophy using optical coherence tomography and fundus autofluorescence.

The Onion Sign in Neovascular Age-Related Macular Degeneration Represents Cholesterol Crystals.

PURPOSE: To investigate the frequency, natural evolution, and histologic correlates of layered, hyperreflective, subretinal pigment epithelium (sub-RPE) lines, known as the onion sign, in neovascular age-related macular degeneration (AMD). DESIGN: Retrospective observational cohort study and experimental laboratory study. PARTICIPANTS: Two hundred thirty eyes of 150 consecutive patients with neovascular AMD and 40 human donor eyes with histopathologic diagnosis of neovascular AMD. METHODS: Spectral-domain optical coherence tomography (SD OCT), near-infrared reflectance (NIR), color fundus images, and medical charts were reviewed. Donor eyes underwent multimodal ex vivo imaging, including SD OCT, before processing for high-resolution histologic analysis. MAIN OUTCOME MEASURES: Presence of layered, hyperreflective sub-RPE lines, qualitative analysis of their change in appearance over time with SD OCT, histologic correlates of these lines, and associated findings within surrounding tissues. RESULTS: Sixteen of 230 eyes of patients (7.0%) and 2 of 40 donor eyes (5.0%) with neovascular AMD had layered, hyperreflective sub-RPE lines on SD OCT imaging. These appeared as refractile, yellow-gray exudates on color imaging and as hyperreflective lesions on NIR. In all 16 patient eyes, the onion sign persisted in follow-up for up to 5 years, with fluctuations in the abundance of lines and association with intraretinal hyperreflective foci. Patients with the onion sign disproportionately were taking cholesterol-lowering medications (P=0.025). Histologic analysis of 2 donor eyes revealed that the hyperreflective lines correlated with clefts created by extraction of cholesterol crystals during tissue processing. The fluid surrounding the crystals contained lipid, yet was distinct from oily drusen. Intraretinal hyperreflective foci correlated with intraretinal RPE and lipid-filled cells of probable monocytic origin. CONCLUSIONS: Persistent and dynamic, the onion sign represents sub-RPE cholesterol crystal precipitation in an aqueous environment. The frequency of the onion sign in neovascular AMD in a referral practice and a pathology archive is 5% to 7%. Associations include use of cholesterol-lowering medication and intraretinal hyperreflective foci attributable to RPE cells and lipid-filled cells of monocyte origin.

OUTER RETINAL TUBULATION IN ADVANCED AGE-RELATED MACULAR DEGENERATION: Optical Coherence Tomographic Findings Correspond to Histology.

PURPOSE: To compare optical coherence tomography (OCT) and histology of outer retinal tubulation (ORT) secondary to advanced age-related macular degeneration in patients and in postmortem specimens, with particular attention to the basis of the hyperreflective border of ORT. METHOD: A private referral practice (imaging) and an academic research laboratory (histology) collaborated on two retrospective case series. High-resolution OCT raster scans of 43 eyes (34 patients) manifesting ORT secondary to advanced age-related macular degeneration were compared to high-resolution histologic sections through the fovea and superior perifovea of donor eyes (13 atrophic age-related macular degeneration and 40 neovascular age-related macular degeneration) preserved ≤4 hours after death. RESULTS: Outer retinal tubulation seen on OCT correlated with histologic findings of tubular structures consisted largely of cones lacking outer segments and lacking inner segments. Four phases of cone degeneration were histologically distinguishable in ORT lumenal walls, nascent, mature, degenerate, and end stage (inner segments and outer segments, inner segments only, no inner segments, and no photoreceptors and only Müller cells forming external limiting membrane, respectively). Mitochondria, which are normally long and bundled within inner segment ellipsoids, were small and scattered within shrunken inner segments and cell bodies of surviving cones. A lumenal border was delimited by an external limiting membrane. Outer retinal tubulation observed in closed and open configurations was distinguishable from cysts and photoreceptor islands on both OCT and histology. Hyperreflective lumenal material seen on OCT represents trapped retinal pigment epithelium and nonretinal pigment epithelium cells. CONCLUSION: The defining OCT features of ORT are location in the outer nuclear layer, a hyperreflective band differentiating it from cysts, and retinal pigment epithelium that is either dysmorphic or absent. Histologic and OCT findings of outer retinal tubulation corresponded in regard to composition, location, shape, and stages of formation. The reflectivity of ORT lumenal walls on OCT apparently does not require an outer segment or an inner/outer segment junction, indicating an independent reflectivity source, possibly mitochondria, in the inner segments.

Subretinal drusenoid deposits in non-neovascular age-related macular degeneration: morphology, prevalence, topography, and biogenesis model.

PURPOSE: To characterize the morphology, prevalence, and topography of subretinal drusenoid deposits, a candidate histological correlate of reticular pseudodrusen, with reference to basal linear deposit (BlinD), a specific lesion of age-related macular degeneration, and to propose a biogenesis model for both lesion. METHODS: Donor eyes with median death-to-preservation of 2:40 hours were postfixed in osmium tannic acid paraphenylenediamine and prepared for macula-wide high-resolution digital sections. Annotated thicknesses of 21 chorioretinal layers were determined at standard locations in sections through the fovea and the superior perifovea. RESULTS: In 22 eyes of 20 white donors (83.1 ± 7.7 years), SDD appeared as isolated or confluent drusenoid dollops punctuated by tufts of retinal pigment epithelium apical processes and associated with photoreceptor perturbation. Subretinal drusenoid deposits and BlinD were detected in 85 and 90% of non-neovascular age-related macular degeneration donors, respectively. Subretinal drusenoid deposit was thick (median, 9.4 µm) and more abundant in the perifovea than in the fovea (P < 0.0001). BlinD was thin (median, 2.1 µm) and more abundant in the fovea than in the perifovea (P < 0.0001). CONCLUSION: Subretinal drusenoid deposits and BlinD prevalence in age-related macular degeneration eyes are high. Subretinal drusenoid deposits organized morphology, topography, and impact on surrounding photoreceptors imply specific processes of biogenesis. Contrasting topographies of subretinal drusenoid deposits and BlinD suggest relationships with differentiable aspects of rod and cone physiology, respectively. A 2-lesion 2-compartment biogenesis model incorporating outer retinal lipid homeostasis is presented.