Evaluation of choriocapillaris (CC) density and RPE morphology in geographic atrophy (GA) due to age-related macular degeneration (AMD) in a one year follow-up including optical coherence tomography angiography (OCTA) and polarization sensitive OCT (PS-OCT)

Abstract

Purpose : Geographic atrophy (GA), the stage leading to irreversible visual loss in age-related macular degeneration (AMD) is a major cause of visual impairment in the industrialized world. OCT Angiography has shown the ability to visualize impaired flow in the choriocapillaris (CC) layer within atrophic lesions whereas PS-OCT allows evaluation of the RPE layer. The purpose of this study was to assess changes of the CC architecture and RPE morphology in GA over a year.

Methods : Fifteen eyes of 12 patients with GA due to AMD were imaged using OCTA (AngioVue, Optovue) for vascular imaging, a wide-field polarisation-sensitive OCT to evaluate the RPE layer and lesion size and fundus autofluorescence (FAF). En face color-coded thickness maps of RPE were segmented. Acquired OCTA CC scans, PS-OCT RPE maps and FAF were overlaid to compare changes between baseline and one year follow-up at each characteristic layer level.

Results : Mean lesion size as assessed by PS-OCT was 8.28 mm² (SD: 3.18 mm²) at baseline and 10.29 mm² (SD: 3.98 mm²) after one year. In all 11 eyes OCTA maps showed distinct areas of CC alterations within the region of GA at baseline. In all eyes these areas of CC alterations enlarged over a year, even exceeding new GA margins in places. In 4 eyes with foveal sparing the mean size of sparing area was 1.63 mm² (SD: 0.37 mm²) at BSL respectively 1.16 mm² (SD: 0.36 mm²) after one year and CC scans displayed an increase in flow impairment area partially even under intact RPE. PS-OCT follow-up evaluation revealed changes in regions of increased depolarizing material consistent with RPE thickening and shedding in the lesion transition zone over time.

Conclusions : A one year follow-up evaluation of multimodal imaging enables a precise delineation of GA lesion growth and associated changes at the different compartments likely involved in GA development such as RPE and choriocapillars. OCTA revealed progression of distinct alterations of CC density in GA lesions and regions of foveal sparing. Alterations of the CC and accumulation of lipofuscin and RPE condensation seen at the GA lesion borders and their changes over time might be pathognomonic events in GA development and could lead to new tools for disease prognosis and therapeutic targets.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.