Evaluation of choriocapillaris (CC) density in geographic atrophy (GA) due to age-related macular degeneration (AMD) in a multimodal imaging approach including optical coherence tomography angiography (OCTA)

Abstract

Purpose : Advanced retinal imaging allows to identify distinct morphological features at different levels of the retina, retinal pigment epithelium (RPE) and choriocapillary (CC). The purpose of this study was to assess GA in a multimodal imaging approach focusing on alterations at the level of the choriocapillary (CC) layer and lesion demarcation.

Methods : Twenty-five eyes of 18 patients with GA due to AMD were imaged using OCTA (AngioVue, Optovue) for vascular imaging, fundus autofluorescence (FAF) for lesion size determination and a wide-field polarisation-sensitive OCT to delineate the RPE layer. CC architecture was either defined as missing (CC density loss), reduced (CC density decrease) or unremarkable (well-preserved). Acquired multimodal maps were overlaid to assess lesion area, border and extralesional zone at each characteristic layer level.

Results : Mean lesion size as assessed by FAF was 8.41 mm² (SD: 3.76 mm²). The multimodal approach for GA visualization allowed a precise discrimination of lesion size and borders at each morphological level. All 25 eyes showed a distinct area of CC alterations within the region of GA. In 3 eyes a complete decrease and in 2 eyes a complete loss of CC density was observed. The majority of lesions (20 eyes) demonstrated irregular mixed patterns of different focal CC alterations.
Sixteen eyes showed a focal loss of CC within the GA lesion, 20 eyes a focal decrease in CC density and 9 eyes showed well-preserved CC densities within the FAF-demarcated GA lesion (CC loss+decrease: 11 eyes; CC decrease+well-preserved: 4 eyes; CC loss+decrease+well-preserved: 5 eyes). A loss of CC density in extralesional areas was seen in none of the eyes examined. In 21 of 25 eyes, a CC-hypodense halo was observed in border regions of GA as assessed by OCTA corresponding to hyperfluorescent areas in FAF and regions of increased depolarizing material in PS-OCT consistent with RPE thickening and shedding.

Conclusions : Multimodal imaging enables a precise delineation of GA lesion size and associated changes in retina, RPE and choriocapillary. OCTA revealed distinct alterations of CC density in GA lesions in all eyes investigated. Reduced blood flow and accumulation of lipofuscin and RPE condensation seen at the GA lesion borders might be pathognomonic events in GA development.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.