Correlations between Choriocapillaris Flow Deficits around Geographic Atrophy and Enlargement Rates Based on Swept-Source OCT Imaging

Abstract

To determine the possible correlation between the annual enlargement rates (ERs) of geographic atrophy (GA) with the percentage and size of the choriocapillaris (CC) flow deficits (FDs) surrounding GA, measured with swept-source OCT angiography (SS-OCTA) images. Prospective, observational case series. Patients with GA secondary to nonexudative AMD. Patients were imaged with a 100-kHz SS-OCTA instrument (PLEX Elite 9000, Carl Zeiss Meditec, Dublin, CA) using a 6×6-mm field of view scan pattern. The GA area measurements were obtained from en face SS-OCT sub-retinal pigment epithelium (RPE) slab images. Visualization of the CC and quantification of FDs were performed using a previously published validated algorithm based on a 20-μm thickness slab with the inner boundary located beneath Bruch's membrane. The percentage of CC FDs (FD%) and the average FD area measurements were calculated in different regions around the GA. The correlation between the CC FDs and the ERs of GA. Twenty-two eyes from 15 patients were eligible for the analysis. The annual square root ERs for GA ranged from 0.07 to 0.75 mm/year. The CC FD% and average FD area measurements were highly correlated with each other (P < 0.001), with the highest FD values found in the region closest to the margin of GA. The ERs correlated best with the average CC FD area measurements in the total scan area minus the area of GA (Pearson r= 0.747; P < 0.001) than those in the regions immediately surrounding the GA (r = 0.544; P= 0.009). Contrary to expectations, the global CC FD measurements had a better correlation with the ERs of GA than those in the regions immediately around the GA. The most likely explanation for this outcome is that normal age-related increases in FDs within the central macula confound the correlations between the ERs of GA and FDs, whereas the regions furthest away from the margins of GA are less affected by normal age-related changes and reflect FD alterations related to AMD severity.