Abstract
Purpose:
Optic nerve head (ONH) and choroidal (Ch) vasoreactivity to hypoxia is not clearly defined, although it is a common pathological situation in diabetic retinopathy, retinopathy of prematurity, open-angle glaucoma or in systemic diseases. We measured ocular blood flow changes in response to acute hypoxia in healthy humans.
Methods:
Using confocal laser Doppler flowmetry, ONH and Ch blood flow were measured under hypoxia condition during 15 minutes (FiO2 10,5%) in order to reach a stable 85% SpO2. PetCO2, blood pressure, and respiratory rate were monitored during the experiment.
Results:
Fourteen young (28±6 years ) healthy subjects were included. In response to 85% hypoxia, ONH blood flow increased of +11% [−2.4; 34] (median and interquartiles interval, p=0.08) mainly due to an increase in ONH velocity +18% [6; 27] (p=0.004). Choroidal LDF parameters did not significantly differ during hypoxia (p=0.2 for Ch flow, p=0.3 for Ch volume, and p=0.12 for Ch velocity). Respiratory rate or arterial pressure did not significantly change during experiment.
Conclusions:
The response of ONH to hypoxia is close to that described for the retina. The absence of choriocapillaris vasoreactivity to hypoxia, despite a significant decrease in tissue oxygen partial pressure, could be explained by the conterbalanced vasoconstriction associated with the activation of the autonomic nervous system during hypoxia.