Interocular symmetry in dynamic retinal vessel analysis among healthy adults

Dynamic retinal vessel analysis is a non-invasive approach for assessing retinal microvascular endothelial function, yet the extent to which eye selection, interocular variability, and systemic physiological factors influence dynamic retinal vessel analyzer (DRVA)-derived biomarkers remains insufficiently defined. This prospective methodological study aimed to evaluate the interocular symmetry and absolute and relative reliability of arterial flicker-induced dilation (aFID), venular flicker-induced dilation (vFID), and arteriolar constriction (aCON), and to determine whether these parameters are moderated by eye dominance, peak oxygen uptake (V̇O₂ peak), or intraocular pressure (IOP) in healthy individuals. Twenty apparently healthy adults completed two laboratory visits. During the first visit, aerobic capacity was assessed by cardiopulmonary exercise testing until volitional exhaustion. During the second visit, IOP, resting blood pressure, eye dominance, and retinal vascular endothelial function were assessed using DRVA in both eyes in randomized order. Interocular differences were examined using paired comparisons, Bland-Altman analysis, reliability statistics, and linear mixed-effects models accounting for bilateral measurements within participants. No significant differences were observed between the left and right eyes for aFID, vFID, or aCON. Bland-Altman analysis showed no systematic interocular bias across DRVA-derived parameters, although the limits of agreement were widest for aFID, indicating greater interocular variability. Relative reliability was highest for vFID, followed by aCON, whereas aFID showed only fair agreement. Similarly, absolute reliability analyses identified vFID as the most stable biomarker, with the lowest coefficient of variation, while aFID demonstrated the greatest variability. Linear mixed-effects models showed no significant moderating effects of eye dominance, V̇O₂ peak, or IOP on aFID, vFID, or aCON. These findings suggest that retinal vascular endothelial responses measured by DRVA are not systematically influenced by eye dominance or selected systemic physiological factors in healthy young adults. However, given the observed interocular variability, particularly for aFID, assessment of both eyes should be considered in clinical and research settings to improve measurement precision and reproducibility.