Choriocapillaris atrophy in ABCA4 retinopathy is secondary to retinal pigment epithelium impairment

Abstract

Purpose : To compare choriocapillaris (CC) and retinal pigment epithelium (RPE) impairment and progression, as measured by optical coherence tomography angiography (OCT-A) and short wavelength autofluroescence (SW-AF), respectively, in patients with Stargardt disease.

Methods : OCT-A and SW-AF images were acquired from 20 patients (40 eyes) with a clinical and genetic diagnosis of Stargardt disease. 12 patients (24 eyes) were imaged at a single visit and 8 patients (16 eyes) were imaged at two separate visits at least 9 months apart. The clinical diagnosis of Stargardt disease was made by an inherited retinal disease specialist (SHT) based on fundus features, symptoms, imaging, and confirmed genetic sequencing results. The area of CC and RPE impairment as observed on OCT-A and SW-AF, respectively, was manually outlined and measured by two independent observers. Rates of progressive CC and RPE impairment were calculated for the cohort of patients imaged at two visits. Comparative statistics was used to calculate differences between the mean areas of CC and RPE impairment as well as differences in disease progression rates.

Results : Among the cohort of 12 patients (24 eyes) with a single time point, the mean area of CC impairment on OCT-A and RPE impairment on SW-AF were 2.98 ± 0.63 mm² and 4.04 ± 0.90 mm², respectively. Comparative analysis revealed a significant difference between the average values of CC and RPE impairment (P = 0.003). The mean follow-up time among the cohort of 8 patients (16 eyes) imaged at two separate visits was 1.03 ± 0.12 years. The mean CC impairment progression rate was 0.33 ± 0.12 mm²/year, which was found to be significantly different from the mean RPE impairment progression rate of 0.64 ± 0.23 mm²/year (P = 0.024).

Conclusions : Our results support previous studies that have shown that CC atrophy occurs secondary to RPE impairment in Stargardt pathophysiology. RPE impairment occurs at a higher rate than CC impairment in patients with Stargardt disease, contributing to comparatively larger areas of RPE than CC atrophy at any given time point as observed on SW-AF and OCT-A, respectively.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.