Choroidal Vascularity Index in Geographic Atrophy secondary to dry Age Related Macular Degeneration

Abstract

Purpose : Geographic atrophy (GA) is a chronic progressive degeneration of the macula and is considered the late stage of dry age-related macular degeneration (AMD). Choroidal thickness is known to be reduced in AMD eyes with GA compared to normal eyes, but less is known about changes in choroidal vascularity index (CVI). In this study, we evaluate CVI in subjects with fovea sparing (FS) and fovea involving (FI) GA secondary to dry AMD.

Methods : In this post-hoc analysis of subjects enrolled into a population study of elderly Amish individuals, we identified 44 subjects and 63 eyes with GA (24 eyes - fovea spared GA; 39 eyes - fovea involved) and 61 normal healthy eyes. All subjects underwent spectral domain optical coherence tomography (SD-OCT) scanning with a Cirrus OCT, and a single OCT B-scan passing through the foveal center was selected for analysis. The choroid was automatically segmented into luminal and stromal areas using a previously described binarization method (all pixels classified as either vessel or stroma), and the CVI (%) was calculated as ratio of luminal area to total choroid area. Choroidal thickness (CT) was measured at the foveal center using the caliper tool. CVI and choroidal thickness were compared among foveal-involved GA eyes, fovea-spared GA eyes, and normal eyes.

Results : There was a significant difference in age (p=0.001) between healthy controls (71.26± 11.6 yrs) and patients with GA (78.4 ± 9.4 yrs). After controlling for age, there was no significant difference (p=0.320) in CT between patients with GA (232.9 ± 20.6 µm) and aged matched normals (241.7 ± 66.4 µm). CT was not significantly different (p=0.44) between fovea involved (230 ± 18 µm) and fovea spared (234 ± 22 µm) groups.
CVI was found to be significantly different (p<0.001) between patients with GA (59.47± 0.20%) and age matched controls (52.77 ± 7%). CVI was also found to be significantly higher (p<0.03) in fovea spared GA (60 ± 2.1%) when compared to patients with fovea involved GA (59 ± 2.0%).

Conclusions : The CVI was higher in subjects with GA compared to healthy controls, and notably, CVI was higher in fovea-sparing GA, compared to fovea-involving GA. However choroidal thickness showed no difference between groups. The relevance of CVI in GA warrants further investigation.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.