OCT Angiography-Derived Retinal Microvascular Changes in Diabetic and Non-Diabetic Eyes and Their Relationship to Disease Severity: A Cross-Sectional Study

Purpose: To quantitatively evaluate retinal microvascular metrics on optical coherence tomography angiography (OCTA) and determine their association with diabetes status and diabetic retinopathy (DR) severity. Methods: This prospective observational study included 107 eyes from adults with and without diabetes, imaged between March and August 2025 at Drashti Netralaya, Dahod, Gujarat. High-resolution OCTA (Heidelberg Spectralis) with OCTEVA software was used for automated segmentation of the superficial (SCP), intermediate (ICP), and deep capillary plexuses (DCP). Quantitative metrics included vessel area density, branchpoint density, fractal dimension, vessel length density, and foveal avascular zone (FAZ) area. DR severity was graded using ETDRS criteria, and eyes were stratified by insulin dependence, clinically significant macular oedema (CSME), and diabetes duration. Group differences were assessed using Mann–Whitney U and Kruskal–Wallis tests with Holm–Bonferroni correction for multiple comparisons. Results: Diabetic eyes showed reduced vessel density (SCP: 48.3 ± 5.6% vs. 53.1 ± 6.1%, P = 0.002; ICP: 35.4 ± 4.7% vs. 39.2 ± 4.9%, P = 0.004; DCP: 36.0 ± 4.8% vs. 40.7 ± 5.2%, P < 0.001) and enlarged FAZ (0.34 ± 0.07 mm 2 vs. 0.28 ± 0.05 mm 2 , P = 0.003) compared with controls. DR severity correlated with progressive rarefaction and reduced fractal dimension, most prominent in the DCP ( P < 0.001). CSME eyes had increased central macular thickness (326.4 ± 32.5 µm vs. 287.3 ± 26.7 µm, P < 0.001). Insulin dependence and longer diabetes duration (>15 years) were linked to significant microvascular loss ( P < 0.05). Conclusion: OCTA-derived metrics sensitively detect early and progressive microvascular compromise in diabetes, with the DCP most vulnerable. Stratification by DR severity and risk factors demonstrates OCTA’s potential as a biomarker for disease progression and a tool for early intervention.