Abstract
Age-related macular degeneration (AMD) is a leading cause of central vision loss worldwide. The progression of dry AMD from early to intermediate stages is primarily characterized by increasing drusen formation and adverse impact on outer retinal cells. Late stage AMD consists of either geographic atrophy (GA), the non-exudative (dry) AMD subtype, or choroidal neovascularization, the exudative (wet) AMD subtype. GA is characterized by outer retinal and choroidal atrophy, specifically the photoreceptor layer, RPE, and choriocapillaris. Much remains to be discovered regarding the pathogenesis of AMD progression and subsequent development of GA. As the functionality of all three layers is closely linked, the temporal sequence of events that end up in atrophy is important in the understanding of the pathogenic pathway of the disease. The advent of OCTA, and particularly of swept-source technology, has allowed for depth-resolved imaging of retinal vasculature and the choriocapillaris. With the use of OCTA, recent studies demonstrate that choriocapillaris flow alterations are closely associated with the development and progression of AMD. Such changes may even possibly offer predictive value in determining progression of GA. This article reviews studies demonstrating choriocapillaris changes in dry AMD and summarizes the existing literature on the potential role of the choriocapillaris as a key factor in the pathogenesis of AMD.
Highlights
The prevalence of age-related macular degeneration (AMD), currently at 6.5% [1] in the US population aged 40 years and above, continues to expand, and is projected to globally affect 196 million people by 2020 [2]
On OCT, classical geographic atrophy (GA) is characterized by atrophy of the outer nuclear layer, external limiting membrane (ELM), ellipsoid zone (EZ), photoreceptors, retinal pigment epithelium (RPE), and choriocapillaris (CC), in the setting of characteristic extracellular deposits, causing increased transmission of the OCT signal below Bruch’s membrane [16]
We performed a review of histopathological and OCT/OCT angiography (OCTA) imaging studies to explore the role of the choriocapillaris (CC) in the pathogenesis of dry AMD
Summary
The prevalence of age-related macular degeneration (AMD), currently at 6.5% [1] in the US population aged 40 years and above, continues to expand, and is projected to globally affect 196 million people by 2020 [2]. OCT angiography (OCTA), as a non-invasive, depth-resolved imaging modality has allowed us to explore the role of choroidal vasculature in the pathogenesis of AMD [10–12]. On OCT, classical GA is characterized by atrophy of the outer nuclear layer, external limiting membrane (ELM), ellipsoid zone (EZ), photoreceptors, retinal pigment epithelium (RPE), and choriocapillaris (CC), in the setting of characteristic extracellular deposits, causing increased transmission of the OCT signal below Bruch’s membrane [16].
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