Tibial Artery Hemodynamics Predict Foveal Avascular Zone Enlargement in Type 2 Diabetes

(1) <b>Background</b>: Diabetic retinopathy and peripheral arterial disease co-occur through shared endothelial pathophysiology. Ankle-brachial index (ABI), the standard peripheral screening tool, demonstrates poor sensitivity (35%) in diabetic cohorts due to medial arterial calcification. We comparatively assessed the association of peak-systolic velocity of posterior/anterior tibial artery ratio (PT:AT) versus that of traditional pressure-based (ABI) with foveal avascular zone (FAZ), a marker of retinal ischemia, and thus hypothesized that PT:AT would demonstrate stronger association with FAZ compared to ABI in our cohort. (2) <b>Methods</b>: Cross-sectional pilot study of 30 type 2 diabetes mellitus patients. We aimed to enhance the robustness of our results using five convergent statistical methods. (3) <b>Results</b>: PT:AT showed strong association with FAZ (r = 0.471, <i>p</i> = 0.0086, 95% CI [0.13, 0.71]), with convergent evidence across all five analytical methods. ABI showed no effect (r = -0.024, <i>p</i> = 0.901, 95% CI [-0.38, 0.34]). We showed that velocity-based metrics identify microvascular dysfunction, whereas the pressure-based ABI does not. The mediation analysis showed that the relation of PT:AT to FAZ is not significantly mediated by the resistivity index of ophthalmic artery. (4) <b>Conclusions</b>: In this pilot study, velocity-based tibial hemodynamics showed a stronger cross-sectional relationship with retinal microvascular damage compared to pressure-based ABI. These preliminary findings suggest PT:AT assessment may complement ABI screening in diabetic foot clinics to identify patients requiring intensive retinal surveillance. Multicenter validation is required before clinical implementation.