Macular choriocapillaris perfusion and outer retinal layer thickness measurements correlate with low luminance visual acuity deficits

Abstract

Purpose : Swept-source optical coherence tomography angiography (SS-OCTA) was used to investigate the correlations between central choriocapillaris (CC) perfusion deficits and other macular structural characteristics with low luminance visual acuity deficit (LLVAD) measurements. Most importantly, correlations between LLVAD and central CC perfusion deficits were investigated to help explain how increases in LLVAD measurements at baseline have been shown to predict the growth rate of geographic atrophy (GA).

Methods : Photopic luminance best-corrected visual acuity (PL-BCVA) and low luminance BCVA (LL-BCVA) were measured using the Early Treatment Diabetic Retinopathy Study chart. LL-BCVA was measured using a 2.0-log unit neutral density filter. LLVADs were calculated as the difference between the PL-BCVA and LL-BCVA letter scores. Within a fovea-centered 1mm circle, the percentage of choriocapillaris flow deficits (CC FD%), optical attenuation coefficient (OAC) elevation volume (analogous to drusen volume), and the outer retinal layer (ORL) thickness were assessed.

Results : In all 90 eyes (30 normal eyes; 31 drusen-only eyes; 29 non-foveal geographic atrophy eyes), significant correlations were found between the central CC FD% and PL-BCVA (r= -0.393, p<0.001), LL-BCVA (r= -0.534, p<0.001), and LLVAD (r= 0.439, p<0.001). Central cube root (cubrt) OAC elevation volume and ORL thickness were also significantly correlated with PL-BCVA, LL-BCVA and LLVAD (all p<0.05). Stepwise regression models showed central cubrt OAC elevation volume and ORL thickness were associated with PL-BCVA (R²=0.24, p<0.05). Central CC FD%, cubrt OAC elevation volume and ORL thickness were associated with LL-BCVA (R²=0.44, p<0.01). Central CC FD% and ORL thickness were associated with LLVAD (R²=0.24, p<0.01).

Conclusions : The significant correlations between central CC FD% and both LL-BCVA and LLVAD measurements support the hypothesis that decreases in central macular CC perfusion impact foveal cone photoreceptor function, especially under low luminance. Since we know that decreased CC perfusion within the macula correlates with increased growth rates of GA, it now seems reasonable to conclude that the significant correlation between central CC FD% and LLVAD measurements explains how an increase in LLVAD measurements at baseline predicts an increase in the growth rates of GA over time.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.