Optical Coherence Tomography Angiography Findings in Diabetic Retinopathy: A Clinical Comparative Study

Background: Diabetic retinopathy (DR) remains a leading cause of preventable blindness worldwide. Optical coherence tomography angiography (OCTA) is a novel, non-invasive imaging technology that enables visualization of retinal and choroidal microvasculature without the need for dye injection. This study aimed to characterize OCTA-derived vascular parameters in different stages of diabetic retinopathy and compare them with conventional fluorescein angiography (FA) findings. Methods: A prospective, observational comparative study was conducted at a tertiary eye care center between January 2023 and December 2024. A total of 186 eyes from 124 patients with type 2 diabetes mellitus were enrolled and classified into: no apparent DR (NDR, n=42), mild non-proliferative DR (NPDR, n=38), moderate NPDR (n=36), severe NPDR (n=38), and proliferative DR (PDR, n=32). Thirty-two eyes from 20 age-matched healthy controls were also included. All participants underwent OCTA (3×3 mm and 6×6 mm macular scans) and conventional FA. Key OCTA parameters including foveal avascular zone (FAZ) area, vessel density (VD) in the superficial and deep capillary plexuses, and flow area were measured and compared across DR stages. Results: FAZ area showed progressive enlargement with advancing DR severity (controls: 0.28 ± 0.08 mm²; NDR: 0.35 ± 0.11 mm²; mild NPDR: 0.42 ± 0.14 mm²; moderate NPDR: 0.58 ± 0.18 mm²; severe NPDR: 0.71 ± 0.21 mm²; PDR: 0.89 ± 0.26 mm²; p < 0.001 for trend). Superficial capillary plexus (SCP) vessel density decreased significantly from controls (48.2 ± 3.1%) to PDR (32.4 ± 5.8%) (p < 0.001). OCTA detected microaneurysms in 91.3% of eyes compared to 87.1% with FA. OCTA showed excellent correlation with FA for neovascularization detection (κ = 0.88, p < 0.001) and areas of capillary non-perfusion (r = 0.92, p < 0.001). Conclusion: OCTA provides a non-invasive, rapid, and quantitative assessment of retinal microvascular changes in diabetic retinopathy. The progressive enlargement of FAZ and reduction in vessel density correlate strongly with DR severity. OCTA shows excellent agreement with FA for detecting pathological changes while offering the advantages of non-invasiveness, three-dimensional visualization, and quantitative analysis. OCTA is recommended as a complementary tool to FA in the management of diabetic retinopathy.