The light rise of the electrooculogram during hypoxia

We examined the effect of hypoxia on the human light rise measured by electooculography. Experiments were performed on three subjects. EOGs were recorded by conventional methods. The stimulus was a diffuse field dimmed gradually over 30 min from 350 to 0.35 td, followed by a step to 6250 td. Ten minutes before the light step, the observer began inspiration of 10% O₂ to induce hypoxia, or continued breathing air through a mask or breathing tube. Arterial O₂ saturation was monitored continuously with an ear oximeter and during hypoxia decreased from 96-99% to 70-88%. During hypoxia the standing potential increased during the dim light conditions of the ramp. The light step induced only a small further increase in potential. In a second protocol, we examined prolonged hypoxia during continued adaptation to 0.35 td. During prolonged hypoxia, the standing potential returned to nearly its prehypoxic level. Two of three observers showed a subnormal light rise, suggesting that hypoxia has a specific effect on the light rise in addition to the initial elevation of the standing potential in the dark.