Effect of acute hypoxia or hyperoxia on the optic nerve head and choroidal blood flow in healthy humans

This presentation deals with the ocular vasoreactivity to acute hypoxia and hyperoxia in young healthy subjects (n=16). The protocol consisted in a 15-min inhalation of 100% O2 (hyperoxia) or 10.5% O2 + N2 (for a stable SpO2 of 85%, hypoxia) in normocapnic conditions. Blood flow was measured using laser Doppler flowmetry in the subfoveal choroid or at the temporal site of the optic nerve head (ONH). Hypoxia induced a significant 30±10% increase in ONH blood flow (due to simultaneous VEL and VOL rise). Hyperoxia significantly decreased ONH blood flow by 12±7% (due to both VEL and VOL decrease). Choroidal blood flow was not affected by hypoxia or hyperoxia. We will discuss the mechanisms associated with the effect of gas and the difference of response between choroid and ONH.