Impact of Central Choriocapillaris Flow Deficits on Low Luminance Visual Acuity Measurements

Abstract

Purpose : The impact of central choriocapillaris (CC) flow deficits (FDs) on low luminance visual acuity (LLVA) measurements was investigated in pseudophakic normal eyes and in eyes with nonexudative age-related macular degeneration (neAMD) to determine if LLVA measurements correlated with the stage of AMD and its progression.

Methods : Both normal luminance best-corrected visual acuity (NL-BCVA) and low luminance BCVA (LL-BCVA) were obtained using the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. LL-BCVA was measured by using a 2.0-log unit neutral density filter in front of the examined eye (Wratten filter; Kodak, Rochester, NY). LLVA deficit (LLVAD) scores were calculated by subtracting the LL-BCVA from the NL-BCVA letter scores. The percentage of central CC FDs (%FDs) was determined in a 1mm diameter circle centered on the fovea from 6x6 mm scans using swept-source OCT angiography (SS-OCTA) imaging (PLEX^® Elite 9000, Carl Zeiss Meditec, Dublin, CA) along with a previously validated algorithm. Pseudophakic eyes were chosen since an ongoing study determined that cataracts have an unpredictable effect on LLVA measurements. Eyes with neAMD were categorized as drusen-only eyes and eyes with non-foveal geographic atrophy (nfGA). In eyes with nfGA, the posterior margin of atrophy could not be within 150 µm of the foveal center, and the area of nfGA could not comprise more than 10% of the central 1mm circle.

Results : In 30 normal eyes ranging in ages from 56 to 79, there were no statistically significant correlations between the central CC FD% and the NL-BCVA, LL-BCVA, and LLVAD measurements (all |r| values ≤ 0.04, all p-values ≥ 0.85). However, in 27 drusen-only eyes ranging in ages from 67 to 90, significant correlations were found between the central CC FD% and the NL-BCVA (r=-0.49; p=0.010), LL-BCVA (r=-0.65; p<0.001), and LLVAD (r=0.54; p=0.004). Analysis of neAMD eyes with nfGA is currently underway.

Conclusions : In pseudophakic normal eyes, no correlations were identified between the central CC FD% and the NL-BCVA, LL-BCVAD, and LLVAD measurements; however, in drusen-only eyes, an increase in central CC FD% measurements were correlated with decreased NL-BCVA, decreased LL-BCVA, and increased LLVAD measurements. These correlations suggest that increased CC flow impairment impacts foveal photoreceptor function. The analysis of eyes with nfGA is ongoing.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.