Abstract / Summary
Abstract Background/Objectives: To investigate whether glycemic status modifies the association between retinal microvascular density and retinal function in patients with type 2 diabetes mellitus (T2DM) without clinically detectable diabetic retinopathy (DR). Subjects/Methods: This cross-sectional study included 103 patients (206 eyes) with T2DM without clinically detectable DR. Optical coherence tomography angiography quantified parafoveal vessel density (PFVD) and foveal avascular zone circularity, while retinal function was assessed using the RETeval-derived DR score. Multivariable generalized estimating equation models evaluated the associations of HbA1c and PFVD with retinal function and their interaction, accounting for inter-eye correlation. Sensitivity analyses examined HbA1c thresholds of 7.0%, 7.5%, 8.0%, and 8.5%. Results Higher HbA1c was associated with a higher DR score (β = 0.67, 95% CI, 0.28–1.06; P < 0.001), whereas higher PFVD was associated with a lower DR score (β = −0.29, 95% CI, − 0.49 to − 0.09; P = 0.0027). A significant HbA1c × PFVD interaction was observed (β = 0.13, 95% CI, 0.03–0.23; P = 0.0048), indicating attenuation of the inverse PFVD–retinal function association with increasing HbA1c. At the 8.5% threshold, lower PFVD was associated with higher DR scores in patients with HbA1c < 8.5% (β = −0.44 ± 0.10, P < 0.001), but not in those with HbA1c ≥ 8.5% (β = 0.02 ± 0.27, P = 0.96; P for interaction = 0.019). Conclusions Glycemic status modifies the relationship between retinal microvascular density and retinal function before clinically detectable DR. Combining quantitative vascular imaging with objective functional assessment may help identify early diabetic retinal dysfunction.