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Published on: March 12, 2022
Advancing Retinal Vessel Analysis: Reproducibility of Myogenic Constriction and Assessment of Regulatory Capacity
Eva Fleischlin1, Christoph Hauser1, Walthard Vilser2
1Department of Sport, Exercise and Health, Preventive Sports Medicine and Systems Physiology, Medical Faculty, University of Basel, Basel, Switzerland.
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.
