Retinal Blood Flow Increases with Diabetic Retinopathy Severity in Type 2 Diabetes: A Cross-Sectional Study Using Laser Doppler Velocimetry

Retinal arterial blood flow is known to be reduced in patients with type 2 diabetes mellitus (T2D) without diabetic retinopathy (NDR) compared with healthy individuals, yet the hemodynamic changes across the early stages of diabetic retinopathy (DR) remain unclear. This cross-sectional study investigated the association between retinal blood flow (RBF) and DR severity in patients with T2D using laser Doppler velocimetry, which provides absolute measurements of retinal arterial diameter, flow velocity, and volumetric blood flow. A total of 419 participants were included and classified as NDR (n = 323), mild non-proliferative DR (NPDR; n = 60), moderate NPDR (n = 8), or severe NPDR (n = 28). Median RBF increased progressively with DR severity, measuring 9.8, 10.6, 11.9, and 11.6 µl/min, respectively. Trend analysis using the Jonckheere–Terpstra test demonstrated a significant positive association between RBF and DR stage (p = 0.035). These findings suggest that while RBF is reduced in the earliest stage of diabetes, it subsequently increases with worsening retinopathy, potentially reflecting impaired retinal autoregulation and pressure-dependent hyperperfusion. Measurement of retinal arterial blood flow may therefore serve as a useful hemodynamic marker associated with DR severity in T2D.