Age-related scattered hypofluorescent spots on late-phase indocyanine green angiography: the multimodal imaging and relevant factors

Bruch's Membrane Calcification in Pseudoxanthoma Elasticum: Comparing Histopathology and Clinical Imaging

Purpose

To investigate the histology of Bruch's membrane (BM) calcification in pseudoxanthoma elasticum (PXE) and correlate this to clinical retinal imaging.

Design

Experimental study with clinicopathological correlation.

Subjects and Controls

Six postmortem eyes from 4 PXE patients and 1 comparison eye from an anonymous donor without PXE. One of the eyes had a multimodal clinical image set for comparison.

Methods

Calcification was labeled with OsteSense 680RD, a fluorescent dye specific for hydroxyapatite, and visualized with confocal microscopy. Scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (SEM-EDX) and time-of-flight secondary ion mass spectrometry (TOF-SIMs) were used to analyze the elemental and ionic composition of different anatomical locations. Findings on cadaver tissues were compared with clinical imaging of 1 PXE patient.

Main Outcome Measures

The characteristics and topographical distribution of hydroxyapatite in BM in eyes with PXE were compared with the clinical manifestations of the disease.

Results

Analyses of whole-mount and sectioned PXE eyes revealed an extensive, confluent OsteoSense labeling in the central and midperipheral BM, transitioning to a speckled labeling in the midperiphery. These areas corresponded to hyperreflective and isoreflective zones on clinical imaging. Scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy and TOF-SIMs analyses identified these calcifications as hydroxyapatite in BM of PXE eyes. The confluent fluorescent appearance originates from heavily calcified fibrous structures of both the collagen and the elastic layers of BM. Calcification was also detected in an aged comparison eye, but this was markedly different from PXE eyes and presented as small snowflake-like deposits in the posterior pole.

Conclusions

Pseudoxanthoma elasticum eyes show extensive hydroxyapatite deposition in the inner and outer collagenous and elastic BM layers in the macula with a gradual change toward the midperiphery, which seems to correlate with the clinical phenotype. The snowflake-like calcification in BM of an aged comparison eye differed markedly from the extensive calcification in PXE.

Financial Disclosures

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

Value and Significance of Hypofluorescent Lesions Seen on Late-Phase Indocyanine Green Angiography

Background and Purpose

The hypofluorescence of fundus lesions observed during the late phase of indocyanine green angiography (ICGA) in various diseases has often been overlooked or misinterpreted. This article explores the significance of fundus lesions that are initially isofluorescent during the early phase of ICGA but become hypofluorescent later in the examination.

Findings

Pathologies such as multiple evanescent white spot syndrome, acute posterior placoid syphilitic chorioretinitis, chronic central serous chorioretinopathy, choroidal hemangioma, and some fundus with drusen, present this phenomenon of late hypofluorescence.

Interpretation

The interpretation of ICGA images and the role of indocyanine green (ICG) uptake by the retinal pigment epithelium (RPE) in late fundus fluorescence is debated. Experimental evidence suggests that ICG accumulates progressively in the RPE after intravenous injection of the dye or after direct contact in vitro, making it a potential marker of RPE activity. Although the exact mechanisms of ICG diffusion through the choroid and its binding to the RPE require further investigation, the late hypofluorescence observed in certain ICGA diseases provides information on different modalities of RPE dysfunction.

Financial Disclosures

The author has no proprietary or commercial interest in any materials discussed in this article.

Incidence and multimodal imaging characteristics of macular neovascularisation subtypes in Chinese neovascular age-related macular degeneration patients

AIMS

To investigate the incidence of macular neovascularisation (MNV) subtypes of neovascular age-related macular degeneration (nAMD) and summarise these subtypes' clinical features in the Chinese population using multimodal imaging.

METHODS

We retrospectively analysed 506 consecutive treatment-naïve nAMD patients (582 eyes). Incidence of MNV subtypes and clinical features were recorded based on their multimodal images. The classification of MNV subtypes in nAMD patients were referred to Consensus on Neovascular Age-related Macular Degeneration Nonmenclature (CONAN) study group classifications.

RESULTS

460 eyes of 389 nAMD patients were included in our study. 68.5% (315/460) of nAMD eyes were from male. According to CONAN, we identified type 1 macular neovascularisation (MNV) in 61.1% of eyes (281/460), type 2 MNV in 16.3% of eyes (75/460), type 3 MNV in 2.0% of eyes (9/460), mixed type 1 and type 2 MNV in 20.6% of eyes (95/460). 58% of eyes (267/460) were diagnosed as polypoidal choroidal vasculopathy lesions (PCV). 45.2% of eyes (208/460) with PCV lesions were type 1 MNV and 12.8% of eyes (59/460) with PCV lesions were co-occurred with type 2 MNV.

CONCLUSION

Based on the consensus anatomical classification system developed by the CONAN Study Group, we updated the incidence of MNV subtypes and found that PCV was the most common subtype and type 3 MNV was the least common subtype among Chinese nAMD patients. In addition, the co-occurrence of PCV and type 2 MNV was typically observed, and its frequency was reported in our study.

APOB100 transgenic mice exemplify how the systemic circulation content may affect the retina without altering retinal cholesterol input

Apolipoprotein B (APOB) is a constituent of unique lipoprotein particles (LPPs) produced in the retinal pigment epithelium (RPE), which separates the neural retina from Bruch's membrane (BrM) and choroidal circulation. These LPPs accumulate with age in BrM and contribute to the development of age-related macular degeneration, a major blinding disease. The APOB100 transgenic expression in mice, which unlike humans lack the full-length APOB100, leads to lipid deposits in BrM. Herein, we further characterized APOB100 transgenic mice. We imaged mouse retina in vivo and assessed chorioretinal lipid distribution, retinal sterol levels, retinal cholesterol input, and serum content as well as tracked indocyanine green-bound LPPs in mouse plasma and retina after an intraperitoneal injection. Retinal function and differentially expressed proteins were also investigated. APOB100 transgenic mice had increased serum LDL content and an additional higher density HDL subpopulation; their retinal cholesterol levels (initially decreased) became normal with age. The LPP cycling between the RPE and choroidal circulation was increased. Yet, LPP trafficking from the RPE to the neural retina was limited, and total retinal cholesterol input did not change. There were lipid deposits in the RPE and BrM, and retinal function was impaired. Retinal proteomics provided mechanistic insights. Collectively, our data suggested that the serum LDL/HDL ratio may not affect retinal pathways of cholesterol input as serum LPP load is mainly handled by the RPE, which offloads LPP excess to the choroidal circulation rather than neural retina. Different HDL subpopulations should be considered in studies linking serum LPPs and age-related macular degeneration.

Hyperfluorescence of choroidal arteries in the peripheral fundus on late-phase ICGA

AIMS

To correlate the hyperfluorescent lines in the peripheral fundus on late-phase indocyanine green angiography (ICGA) to infrared and optical coherence tomography (OCT) findings.

METHODS

This is a retrospective, cross-sectional study. Multimodal imaging data, including ICGA, fluorescein angiography, infrared imaging, and OCT were analyzed. The hyperfluorescent lines were categorized into 2 grades according to their extents. In addition, serum levels of apolipoprotein (Apo) A and B were measured by enzyme linked immunosorbent assay.

RESULTS

A total of 247 patients who underwent multimodal imaging were reviewed. The hyperfluorescent lines in the peripheral fundus on late-phase ICGA were detected in 96 patients, and were correlated to superficial choroidal arteries by infrared imaging and OCT. The incidence of hyperfluorescent choroidal arteries in the peripheral fundus (HCAP) on late-phase ICGA increased in groups of older ages (0-20 years, 4.3%; 20-40 years, 2.6%; 40-60 years, 48.9%; >60 years, 88.7%; p < 0.001). In addition, the mean age increased with the grades of HCAP (grade 1, 52.3 ± 10.8 years; grade 2, 63.3 ± 10.5 years; p < 0.001). The hyperfluorescence was also detected in posterior choroidal arteries in 11 eyes, all patients in grade 2. There was no significant correlation between grades of HCAP and gender, or serum level of ApoA and ApoB.

CONCLUSION

The occurrence and grades of HCAP increased with age. The superficial location of choroidal arteries in the peripheral fundus exposes their hyperfluorescence on late-phase ICGA. HCAP might reveal the local lipid degeneration of choroidal artery walls, according to ICG binding properties.

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.

AGE-RELATED RETENTIONAL AVASCULAR PIGMENT EPITHELIAL DETACHMENT VIEWED WITH INDOCYANINE GREEN ANGIOGRAPHY

PURPOSE

Age-related scattered hypofluorescent spots on late-phase indocyanine green angiography (ASHS-LIA) might represent hydrophobic neutral lipid deposits in the Bruch membrane. This study aimed to report retentional avascular pigment epithelial detachment (PED) associated with ASHS-LIA.

METHODS

Patients aged ≥50 years who presented a single avascular serous PED without soft drusen or any other retinal or choroidal diseases were retrospectively included. Pigment epithelial detachment was classified as retentional, effusional, or mixed PED based on indocyanine green angiography. Multimodal images were qualitatively and quantitatively evaluated.

RESULTS

This study included 74 eyes of 57 patients. Retentional PED, effusional PED, and mixed PED accounted for 91.9%, 4.1%, and 4.1%, respectively. All PEDs were located in the macular region. Seventeen (29.8%) included patients had bilateral PEDs and all were retentional PEDs with a high level of bilateral consistency in the characteristics of PED and ASHS-LIA. All retentional PEDs were within the bounds of ASHS-LIA. The area of retentional PED increased with the ASHS-LIA grade ( P = 0.030).

CONCLUSION

Most age-related avascular serous PEDs are retentional PEDs. The location and area of retentional PEDs are consistent with the distribution of ASHS-LIA. These findings suggest that the hydrophobic neutral lipid deposits in the Bruch membrane might be involved in the pathogenesis and be a therapeutic target in age-related retentional avascular PED.

The Natural History of Bruch’s Membrane Calcification in Pseudoxanthoma Elasticum

Purpose

To describe the natural history of Bruch’s membrane (BM) calcification in patients with pseudoxanthoma elasticum (PXE).

Design

Retrospective cohort study.

Participants

Both eyes of 120 PXE patients younger than 50 years, 78 of whom had follow-up imaging after more than 1 year.

Methods

All patients underwent multimodal imaging, including color fundus photography, near-infrared reflectance (NIR) imaging, and late phase indocyanine green angiography (ICGA). We determined the distance from the optic disc to the central and temporal border of peau d’orange on NIR, expressed in horizontal optic disc diameter (ODD). The length of the longest angioid streak was classified into 5 zones.

Main Outcome Measures

Age-specific changes of peau d’orange, angioid streaks, and ICGA hypofluorescence as surrogate markers for the extent of BM calcification.

Results

In cross-sectional analysis, longer angioid streaks were associated with increasing age (P < 0.001 for trend). The temporal border of peau d’orange showed a weak association with increasing age (β = 0.02; 95% confidence interval [CI], 0.00–0.04), whereas the central border showed a strong association (β = 0.12; 95% CI, 0.09–0.15). Longitudinal analysis revealed a median shift of the central border to the periphery of 0.08 ODD per year (interquartile range [IQR], 0.00–0.17; P < 0.001). This shift was more pronounced in patients younger than 20 years (0.12 ODD per year [IQR, 0.08–0.28]) than in patients older than 40 years (0.07 ODD per year [IQR, –0.05 to 0.15]). The temporal border did not shift during follow-up (P = 0.69). New or growing angioid streaks were detected in 39 of 156 eyes (25%). The hypofluorescent area on ICGA was visible only in the fourth or fifth decade and correlated with longer angioid streaks.

Conclusions

In PXE patients, the speckled BM calcification slowly confluences during life. The location of the temporal border of peau d’orange remains rather constant, whereas the central border shifts to the periphery. This suggests the presence of a predetermined area for BM calcification. A larger ICGA hypofluorescent area correlates with older age and longer angioid streaks, which implies that it depends on the degree of BM calcification.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Age-Related Scattered Hypofluorescent Spots on Late-Phase Indocyanine Green Angiography as Precursor Lesions of Polypoidal Choroidal Vasculopathy

Purpose

Age-related scattered hypofluorescent spots on late-phase indocyanine green angiography (ASHS-LIA) might represent lipid accumulation in Bruch's membrane in the form of basal linear deposits (BlinD). The present study was conducted to describe the clinical characteristics of polypoidal choroidal vasculopathy (PCV) associated with ASHS-LIA.

Methods

Consecutive patients with treatment-naïve PCV who underwent color fundus photography (FP), fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), and spectral-domain optical coherence tomography (SD-OCT) at the Zhongshan Ophthalmic Center from June 2016 through May 2018, were reviewed. ASHS-LIA and choroidal vascular hyperpermeability (CVH) were evaluated by ICGA. Subfoveal choroidal thickness (SFCT) was assessed by SD-OCT.

Results

A total of 187 patients were eligible for inclusion in this study (mean, 63.2 ± 7.6 years; range, 41-85 years). Of these patients, 117 (62.6%) showed ASHS-LIA, 57 (30.5%) had bilateral lesions and 70 (37.4%) showed CVH. Moreover, compared with patients without ASHS-LIA, PCV patients with ASHS-LIA were older (P = 0.001), more frequently had bilateral lesions (P = 0.001), and less frequently showed CVH (P = 0.006). SFCT in eyes with ASHS-LIA was significantly greater than that in eyes without ASHS-LIA after adjusting for age, sex, and CVH (P = 0.026). Nevertheless, there was no significant difference in best-corrected visual acuity or lesion characteristics between the two groups.

Conclusions

ASHS-LIA, which is very common in PCV patients, might be involved in the pathogenesis of PCV. PCV with ASHS-LIA was more frequently associated with bilateral involvement, less CVH, and a thicker choroid than PCV without ASHS-LIA.

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

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