Inter-eye microvascular asymmetry across stages of diabetic retinopathy: An OCT angiography study

Purpose: To evaluate inter-eye asymmetry in macular microvascular parameters across different stages of diabetic retinopathy (DR) using OCT angiography, and to explore the associations with clinical factors. Methods: This cross sectional study included 442 eyes of 221 patients with diabetes mellitus type 2. Central subfield thickness (CST), area and perimeter of foveal avascular zone (FAZA and FAZP), perfusion density (PD), vessel density (VD), fractal dimension (FD) in superficial and deep capillary plexuses (SCP and DCP) were evaluated. Asymmetry indexes (AI) of these parameters were calculated and compared among DR severity groups. Results: Mean age was 69.09 ± 12.33 years, with 124 males (56.1%). Across DR stages (No DR, n = 168; mild NPDR, n = 46; moderate NPDR, n = 172; severe NPDR, n = 22; PDR, n = 34), interocular comparisons showed that the mean PD, VD and FD were similar between right and left eyes within each stage (all p > 0.05). In eyes with PDR, FAZA and FAZP in SCP and FAZA in DCP were significantly larger in left eyes compared to right eyes, (p < 0.001, p = 0.011, p = 0.002). In multivariate analysis, increased severity of DR was associated with higher FAZA AI in both SCP and DCP (p < 0.05); male sex (p = 0.008) and presence of DME (p = 0.006) were associated with higher FAZA AI in the SCP. Conclusion: Inter-eye asymmetry in retinal microvascular parameters was associated with male sex, increasing severity of DR and presence of DME.