Early Stages of Age-Related Macular Degeneration: Racial/Ethnic Differences and Proposal of a New Classification Incorporating Emerging Concept of Choroidal Pathology

Abstract

The progression of age-related macular degeneration (AMD) is determined by environmental and genetic factors, and phenotypic or molecular risk factors have been investigated extensively. Interestingly, risk factor profiles for advanced AMD differ among individuals, and one of the causes of variation may be explained by their ethnic background. Recent advances in retinal imaging technology have led to the identification of previously unrecognized risk factors for advanced AMD on optical coherence tomography (OCT) and OCT angiography, which expands the concept of traditional imaging risk factors such as drusen and pigmentary abnormalities visible on color fundus photographs. This OCT imaging modality has identified novel pathognomonic changes for early AMD, including the associated photoreceptor, retinal pigment epithelium, and underlying choroidal changes. Regarding features of multimodal imaging associated with the presence or progression of geographic atrophy, there is an international expert consensus classification system; however, features associated with the progression of macular neovascularization (MNV) are still obscure. To make a consensus towards understanding features associated with the risk of MNV, this review focuses on the early stages of AMD by summarizing imaging characteristics and early signs and classifications in view of advanced multimodal imaging technology. Recent evidence suggests that neovascular AMD is not a single disease entity but a heterogeneous disease characterized by MNV. Besides drusen, OCT features associated with pigment abnormalities, such as shallow irregular RPE elevation (SIRE, also known as double-layer sign), pachychoroid pigment epitheliopathy, and choriocapillaris ischemia, seem to confer a high risk of MNV developing, especially for Asian populations.

The Impact of Blood and Urine Biomarkers on Age-Related Macular Degeneration: Insights from Mendelian Randomization and Cross-sectional Study from NHANES

“…A study has shown that CHO is related to the risk of developing early-stage AMD, but this was not confirmed in our study [ 39 ]. The main clinical feature of early AMD is the appearance of drusen, which is directly related to lipid metabolism [ 40 ]. Therefore, combined with our research results, the role of lipid metabolism in the development of early AMD is further confirmed.…”

Age-Related Macular Degeneration: An Exponentially Emerging Imminent Threat of Visual Impairment and Irreversible Blindness

“…Dry AMD, also known as a non-exudative type of macular degeneration, is characterized by the presence of drusen, which are tiny yellow opaque deposits between RPE and BrM [ 49 ]. These extracellular deposits varying in size and density appear as the earliest features of macular degeneration [ 50 ]. AMD is mainly categorized into early, intermediate, and advanced forms.…”

“…The other spectrum of AMD encompasses the neovascular form or exudative/wet type of AMD, where new blood vessels proliferate into the sub-RPE or subretinal spaces [ 50 ]. The development of CNV causes leakage of abnormal vessels resulting in hemorrhage and even serious complications such as RPE detachment, leading to rapid sight loss [ 55 ].…”

Ranibizumab for the treatment of Age-Related Macular Degeneration related research hotspot and dynamic

“…The FFA can categorize n AMD into occult (type 1) MNV, classic (type 2) MNV, microscopic classic MNV, retinal angiomatous proliferation (RAP), and polypoid choroidal vasculopathy (PCV).Farecki et al [36] concluded that type 1 CNVs appeared larger, were poorly demarcated from the peripheral vasculature, and were seen primarily in the choroidal capillary layer, which is in the sub-RPE layer, whereas type 2 CNVs appeared smaller, were more well demarcated, and were predominantly found in the outer layers of the retina, with more extension into the subretinal space.RAP originates from the deep retinal capillary plexus, and its initial location is within the retina, growing toward the RPE.The incidence of RAP in n AMD primary cases is 10-15% [37,38] .PCV was initially recognized as a choroidal disease, and the 2020…”