Relationship between proximity of choriocapillaris flow deficits and enlargement rate of geographic atrophy

To correlate choriocapillaris (CC) flow deficits (FD) in eyes with geographic atrophy (GA) at various distances from the border of the GA lesion with yearly enlargement rate (yER) of GA. In this retrospective study, spectral domain optical coherence tomography (SD-OCT) and SD optical coherence tomography angiography (OCTA) images were collected from patients with GA, who were imaged at Doheny Eye Centers between 2016 and 2018, using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA). All enrolled patients had one baseline 6 × 6 mm OCTA scan and two 6 × 6 mm SD-OCT cubes, one at baseline and one at a follow-up visit at least 12 months later. The border of the GA was manually outlined on the en face OCT fundus image and the yER was calculated after square root transformation. A grid composed of 100-μm-wide successive concentric rings was created around the GA lesion on the OCTA CC slab using ImageJ and the FD% was calculated from the binarized image. FD% from each ring was correlated with the yER of GA. Thirty eyes of 22 patients were included in the study. The mean yER was 0.2 ± 0.15 mm. The FD% in the first five rings (from 0 to 500 μm from the border of GA) was significantly correlated with the yER. However, there was no statistically significant correlation between the yER and CC FD% beyond 500 μm from the GA lesion. Only the choriocapillaris FD% in the 500-μm region immediately surrounding GA lesions appears to predict the rate of enlargement of these lesions.