Abstract
PURPOSE: To assess changes in radial peripapillary capillary (RPC) microvasculature and their impact on visual function, measured by visual acuity (VA) and contrast sensitivity, in diabetic retinopathy (DR). METHODS: This was a cross-sectional study in 96 eyes of 67 patients, including controls, diabetes without DR (DMnoDR), nonproliferative DR (NPDR), and proliferative DR (PDR) groups. Participants underwent same-day quantitative contrast sensitivity function (qCSF) and 6 × 6 mm OCT angiography (OCTA) centered on the optic disc. The Peripapillary Nerve Fiber Layer Microvasculature Density algorithm (ARI Network) was used to calculate capillary perfusion density (total area of perfused microvasculature per unit area), capillary flux index (CFI, total weighted area of perfused microvasculature per unit area), and retinal nerve fiber layer (RNFL) thickness surrounding the optic disc. Mixed-effects multivariable regression models, controlling for age, hypertension, and lens status, evaluated associations between RPC OCTA metrics, DR severity, VA, and qCSF. RESULTS: Significant RPC microvascular changes were observed across DR stages. Capillary perfusion density decreased with DR severity and even before retinopathy onset in DMnoDR versus controls (βavg = -0.42, P = 0.021). PDR compared to NPDR showed a significant decrease in CFI (β = -1.02 to -0.92, P < 0.01) and in RNFL (βavg = -0.71, P = 0.033). CFI had significant associations with qCSF at various spatial frequencies (β = 0.20 to 0.34, P = 0.002 to 0.042), but not with VA. CONCLUSIONS: Radial peripapillary capillary perfusion density worsens with onset of diabetes and increasing severity of DR while capillary flux index is more significantly affected later in disease. Structure-function associations suggest that DR-induced peripapillary microvascular changes are more strongly associated with contrast sensitivity changes than with visual acuity.