Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography

Abstract

To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer.Methods: Twenty-four healthy volunteers participated in this randomized, double-masked, crossover study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusiondensity wascalculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of the gas mixtures. Retinal vessel calibres in major retinal vessels were measured using a dynamic vessel analyzer.Results: During 100% oxygen breathing, a significant decrease in DCP perfusion density from 41.7 AE 2.4 a.u to 35.6 AE 3.1 a.u. (p < 0.001) was observed, which was accompanied by a significant decrease in vessel diameters in majorretinal arteries and veins(p < 0.001 each). No significant change in perfusion density in the SVP occurred (p = 0.33). In contrast, during hypoxia, perfusion density in the SVP significantly increased from 34.4 AE 3.0a.u.to 37.1 AE 2.2 a.u. (p < 0.001), while it remained stable in the DCP (p = 0.25). A significant increase in retinal vessel diameters was found (p < 0.01). Systemic oxygen saturation correlated negatively with perfusion density in the SVP and the DCP and retinal vessel diameters (p < 0.005 each). Conclusion:Our results show that systemic hyperoxia induces a significant decrease in vessel density in the DCP, while hypoxia leads to increased vessel density limited to the SVP. These results indicate that the retinal circulation shows the ability to adapt its blood flow to metabolic changes with high local resolution dependent on the capillary plexus.

Retinal Vascular Physiology Biomarkers in a 5XFAD Mouse Model of Alzheimer’s Disease

“…One possible explanation for this finding is the presence of amyloid angiopathy and thickening of the vessel walls due to the deposition of Aβ. Under physiological conditions, elevated O 2A triggers a regulatory response that leads to vasoconstriction [ 49 ] and reduced TRBF [ 50 ]. However, under pathological conditions as in 5XFAD, the observed increase in O 2A may be attributed to reduced oxygen diffusion across thickened vessel walls upstream of the measured site, in vessels traveling to the eye or even farther along toward the heart.…”

Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters

“…Our results are also consistent with other studies of retinal physiology during hypoxia using OCT-angiography ( 30 – 33 ). In a group of young healthy volunteers, Hommer et al ( 31 ) reported a significant increase in perfusion density within the superficial vascular plexus of the retina during hypoxic challenges. Similarly, Sousa et al ( 33 ) reported a significant increase in both the superficial and deep vascular plexuses.…”

Variability of Vascular Reactivity in the Retina and Choriocapillaris to Oxygen and Carbon Dioxide Using Optical Coherence Tomography Angiography

“…We demonstrate that it is feasible to perform layer-specific analysis of the retinal and choriocapillaris vasculature 18 , 40 and also assess the reactivity of the vascular network in a regional manner using commercially available SS-OCTA. Retinal vascular reactivity assessment has the potential to elucidate vascular abnormalities before the classic signs of vascular abnormalities such as capillary nonperfusion, microaneurysms, or hemorrhage.…”