Spatial analysis of choriocapillaris flow deficits in staged dry AMD using swept-source OCTA

Abstract

Purpose : Age-related macular degeneration (AMD) is a leading cause of vision impairment and loss worldwide. Initial studies have shown that the choriocapillaris in the foveal area appears to be preferentially affected by age. This study used OCTA to investigate variation in CC flow deficits in patients with various stages of AMD with distance from the fovea.

Methods : 3mm x 3mm swept-source (SS-) OCTA images from early dAMD patients (23 eyes) and intermediate dAMD patients (7 eyes) were analyzed using an algorithm to account for drusen shadowing followed by binarization and particle analysis to assess regional flow deficit percentage. Regions were defined by concentric circular areas centered on the fovea: a 1mm diameter circle, a 1.5mm diameter ring, a 2.5mm diameter ring, and a 2.5mm diameter circle. Parallel analysis was undertaken for 6mm x 6mm images (22 early, 8 intermediate dAMD eyes), with concentric circular areas defined by a 1mm diameter circle, a 3mm diameter ring, a 5mm diameter ring, and a 5mm diameter circle. Data were analyzed using simple univariate analysis, then a least-squares fit analysis of covariance to account for effect of age on the CC. A generalized estimating equation (GEE) was used additionally to account for use of fellow eyes in some patients.

Results : There was a significant difference (p < .05) between early and intermediate dAMD groups in none of the 3x3 but all of the 6x6 regions excepting the 5mm diameter ring on univariate analysis. On least-squares analysis of covariance, age but not dAMD stage was significant for all regions, a result that was duplicated using the GEE.

Conclusions : While univariate analysis suggests some significant difference in flow deficit percentage between early and intermediate dAMD groups in certain 6x6 regions, more powerful statistical models accounting for covariance and clustering suggest that any significant differences are more likely attributable to patient age than to the studied dAMD stages. This finding may suggest a strong and regionally-invariant similarity in macular CC density among individuals with early and intermediate dAMD.

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