Advancing Retinal Vessel Analysis: Reproducibility of Myogenic Constriction and Assessment of Regulatory Capacity

Purpose: Accurate characterization of retinal microvascular autoregulation requires reliable assessment of both vasodilatory and vasoconstrictive responses. Although blood pressure (BP)-induced vasoconstriction is well recognized, its measurement lacks reproducibility data, limiting its translational applicability. This study aimed to establish and validate a standardized framework for quantifying BP-induced vasoconstriction and to introduce the control range as a novel metric for retinal microvascular regulatory capacity. Methods: Healthy adults were assessed twice, one week apart. Retinal vessel diameters were continuously measured during isometric handgrip exercise at sub- and maximal contractions to induce BP elevations. Changes in arterial vessel diameters were extracted by subtracting the mean of the lowest 3 seconds from the baseline diameter. Additionally, flicker light-induced dilation was measured, and the range between maximal dilatation and constriction was calculated. Intra-individual reproducibility was assessed via intraclass correlation coefficient (ICC). Results: Twenty-four participants (13 males, 11 females; 43.4 ± 15.1 years) were included. The average reduction in vessel diameter during the maximal handgrip phase was -6.15 ± 3.89 µm (P < 0.01). The intra-individual ICC was 0.87 (95% confidence interval [CI], 0.74-0.95). Based on the independent behavior of vasodilatory and vasoconstrictive responses, the quantified control range was defined as the dynamic range between maximal flicker-induced dilation and pressure-related constriction. Conclusions: This standardized approach enables reproducible quantification of retinal myogenic constriction. The control range may serve as a measure of microvascular regulatory capacity. Translational Relevance: A standardized and reproducible assessment of retinal myogenic constriction and regulatory capacity has the potential for clinical implementation in the risk stratification of cardiovascular disease.