Preretinal oxygen changes in the rabbit under conditions of light and dark.

Preretinal oxygen measurements were made in pigmented rabbits under conditions of light and dark. The avascular rabbit retina was chosen to eliminate the effects of autoregulation by the retinal vasculature, thus more clearly defining the role of the photoreceptors on preretinal measurements of oxygen delivery from the choroid. Measurements were made 50-100 micron away from the retina using oxygen microelectrodes. An average preretinal oxygen value of 9.8 +/- 1.3 SE mm Hg (n = 12) was measured in room light under normoxic conditions. A change from light to dark conditions always resulted in a measured decrease in preretinal oxygen levels. During the first 30 min of dark adaptation, a 25.8% (+/- 5.5% SD) decrease was obtained. This oxygen decrease is reversible during sequential light adaptation, reaching plateau in approximately 15-20 min. These results indicate that the photoreceptors have a significant effect on choroidal oxygen transmission across the retina.