Retinal Capillary Loss Is More Severe in the Midperiphery Than in the Macula in Eyes With Diabetic Retinopathy Compared to Healthy Eyes

Purpose: To determine whether the reduction in retinal capillary density (CD) is uniform across the capillary plexuses, from the foveal center to the midperiphery, in eyes with diabetic retinopathy (DR) compared with healthy eyes. Methods: Twenty-one eyes with nonproliferative or early proliferative DR and 10 healthy eyes were examined using swept-source optical coherence tomography angiography (OCTA). Multiple 3 × 3-mm OCTA scans were acquired to form a horizontal band extending from the fovea to 9 mm temporally. CD was measured in each 0.1-mm sample within each capillary plexus and analyzed using a linear mixed-effects model and a segmented regression. Results: CD was lower in DR eyes than in healthy eyes (adjusted difference: −4.1%, P < 0.001) and decreased toward the temporal midperiphery in all plexuses. The reduction in CD in DR eyes was uniform regardless of eccentricity in the superficial and intermediate plexuses but increased toward the periphery in the deep capillary plexus (DCP) (group × plexus × eccentricity interaction, P < 0.001). After segmented regression, CD in the DCP plateaued beyond 6 mm from the foveal center in healthy eyes but continued to decrease up to 9 mm in DR eyes, where midperipheral loss reached 45% versus 25% in healthy eyes (P < 0.001). Conclusions: In DR eyes, the CD loss from the fovea to the midperiphery varied by plexus, with a stronger peripheral reduction in the DCP beyond 6 mm. Translational Relevance: The preferential midperipheral DCP dropout highlights a plexus-specific, region-dependent pattern of capillary loss, which could serve as an imaging marker of ischemia progression in diabetic retinopathy.