Assessment of retinal vasoreactivity to hyperoxia as a microvascular biomarker using optical coherence tomography angiography.

Clinical relevance: A substantial proportion of mild coronavirus disease 2019 survivors exhibit persistent systemic manifestations despite clinical recovery. Investigating associated vascular biomarkers may provide novel monitoring strategies and elucidate the underlying pathophysiological mechanisms of post-viral sequelae.

Background: The aim of this work is to assess the diagnostic efficacy of vascular reactivity in the retina and compare it with vascular density in the evaluation of systemic damages.

Methods: This observational cross-sectional study included 42 eyes of 24 patients who recovered from mild coronavirus disease 2019 and 18 healthy control volunteers. Optical coherence tomography angiography was used to assess the retinal vessel density. Vasoreactivity was defined as the change from baseline in vessel density after hyperoxia test. Analysis of covariance compared the ratio of intrasubject vessel density change induced by hyperoxia from baseline between the two groups. Retinal layer-specific and region-specific analyses of vasoreactivity were performed.

Results: Vessel density showed no difference between groups. Vasoreactivity of recovered participants was significantly lower than that of controls at the inner retinal level in peripapillary (-0.09 ± 0.04 vs -0.14 ± 0.06, p = 0.005) region. Vasoreactivity exhibited strong diagnostic values (p < 0.05) whereas vessel density did not. Vasoreactivity in deep capillary plexus layer was most prominent after hyperoxic stimulation in peripapillary regions.

Conclusion: The retinal vasoreactivity to hyperoxia is a more reliable indicator of systemic health risks compared to the structural parameters of retinal vessel density. Additionally, retinal vascular reactivity demonstrates spatial heterogeneity regarding region and layer.