Abstract
AIMS: Impaired red blood cell (RBC) deformability is a potential contributor to microvascular dysfunction in diabetes. This study aimed to determine the association between erythrocyte deformability and the severity of diabetic retinopathy (DR), focusing on quantitative measures of macular and peripheral ischemia. METHODS: We retrospectively analyzed 79 patients with treatment-naïve DR. RBC deformability was measured using a microfluidic ektacytometer, and the elongation index at 3 pascals (EI@3P) was calculated. Optical coherence tomography angiography (OCTA) and ultra-widefield fluorescein angiography (UWFFA) were performed to quantify macular vessel density, foveal avascular zone (FAZ) area, and peripheral ischemic index. Associations between EI@3P and imaging parameters were assessed across DR severity groups using correlation and regression analyses. RESULTS: EI@3P significantly decreased with advancing DR stages (P = 0.010). Eyes with lower EI@3P exhibited reduced vessel density and enlarged FAZ in the deep capillary plexus on OCTA (P = 0.042 and P = 0.041, respectively). In severe non-proliferative and proliferative DR, reduced EI@3P was associated with a higher peripheral ischemic index on UWFFA (r = -0.206, P = 0.035). No significant association was observed between EI@3P and glycated hemoglobin or diabetes duration. CONCLUSIONS: Decreased erythrocyte deformability correlates with microvascular ischemia and disease severity in DR, suggesting a hemorheological mechanism linking systemic blood rheology to retinal microcirculatory impairment. EI@3P may serve as a novel biomarker for assessing microvascular complications in diabetes.