Methods: This prospective, observational study included 83 eyes of diabetic patients imaged at Drashti Netralaya, Dahod, Gujarat, between March and August 2025. Participants were stratified by diabetes duration into four groups: <5 years, 5-9 years, 10-14 years, and ?15 years. High-resolution OCTA (Spectralis, Heidelberg Engineering) was used to assess the superficial vascular plexus (SVP) and deep capillary plexus (DCP). Quantitative parameters included central macular thickness (CMT), foveal avascular zone (FAZ) area, vessel area density, vessel length density, branchpoint density, fractal dimension, and mean tortuosity. Continuous data were summarized as mean ± standard deviation, and comparisons across duration groups were performed using non-parametric tests with Holm?s correction for multiple comparisons.

Results: The mean age of participants was 59.9 ± 9.7 years, with 32.5% female representation. Mean diabetes duration was 8.3 ± 6.4 years. CMT varied modestly across groups, ranging from 278.7 ± 74.9 µm (10-14 years) to 295.4 ± 82.3 µm (<5 years). OCTA revealed progressive microvascular compromise with longer diabetes duration, most pronounced in the DCP. DCP FAZ enlarged from 0.52 ± 0.18 mm² (<5 years) to 0.59 ± 0.35 mm² (≥15 years), while vessel area density decreased from 34.7 ± 15.7% to 30.2 ± 12.5%. Fractal dimension and branchpoint density also declined with increasing duration, indicating capillary rarefaction and network simplification.

Conclusions: Spectralis OCTA demonstrates duration-dependent alterations in retinal microvasculature, particularly within the DCP. These findings suggest that OCTA-derived metrics may serve as sensitive biomarkers of cumulative diabetic microangiopathy and support more personalized monitoring strategies. Keywords : Diabetes mellitus; Diabetic retinopathy; Optical coherence tomography angiography; Retinal microvasculature; Foveal avascular zone; Deep capillary plexus; Duration of diabetes