Retinal oxygen tension is higher in light than dark.

The oxygen tension at the inner retinal surface in rabbits was measured with intraocular polarographic electrodes. In the air breathing rabbit, the oxygen tension is 21 +/- 9 mm Hg (mean +/- 1 SD, n = 6) in 12 foot-candles white light at the cornea. The oxygen tension falls 6 +/- 2 mm Hg (mean +/- 1 SD, n = 4, p less than 0.02) in darkness. In bright white light (800 foot-candles), the retinal oxygen tension is about 6 mm Hg higher than at 12 foot-candles. The in vivo retinal oxygen consumption was calculated to be 2.4 ml O2/100 g/min in light and 2.6 ml O2/100 g/min in dark. The higher oxygen consumption is probably responsible for the lower oxygen tension of the retina in dark as compared to light. Breathing 100% oxygen elevates the preretinal oxygen tension to 190 +/- 72 mm Hg (mean +/- 1 SD, n = 4) in light.