Choroidal vascular alterations in diabetic retinopathy and their association with macular microvascular parameters

This study aims to analyze choroidal vasculature changes in Type 2 Diabetes Mellitus (T2DM) patients and their correlation with diabetic retinopathy (DR) progression and macular microvascular parameters. The study enrolled 90 patients with type 2 diabetes mellitus (T2DM), categorized by diabetic retinopathy (DR) severity, alongside 26 non-diabetic controls. Choroidal parameters-including choroidal vascular index (CVI) and subfoveal choroidal thickness (SFCT)-were measured using optical coherence tomography (OCT). Macular microvascular parameters, specifically superficial capillary plexus vascular density (SCPVD), deep capillary plexus vascular density (DCPVD), foveal avascular zone (FAZ) area, and FAZ perimeter (PERIM), were evaluated via OCT angiography (OCTA). As DR progressed, significant decreases were observed in SCPVD, DCPVD, and CVI, along with FAZ expansion. Compared to controls, SCPVD exhibited a marked decrease in mild non-proliferative diabetic retinopathy (NPDR) to proliferative diabetic retinopathy (PDR) groups, DCPVD was substantially reduced in moderate to severe NPDR groups, and CVI was significantly lower in severe NPDR group. Meanwhile, FAZ was notably expanded in moderate NPDR to PDR groups. CVI was positively correlated with DCPVD and negatively with FAZ area. CVI accurately reflects choroidal vascular changes in DR and correlates with deep retinal blood flow and FAZ area, making it an effective metric for assessing choroidal vasculature alterations in DR patients.