Retinal oxygenation from the choroid in hyperoxia.

The extraordinarily high rate of blood flow in the cat choroid allows the choroidal oxygen tension to rise to levels close to the arterial PO2, even with oxygen enriched breathing mixtures. The high PO2 in the choroid can elevate the oxygen tension of the inner retina above the saturation PO2 of hemoglobin when oxygen enriched breathing mixtures at one atmosphere or less are used as shown by polarographic oxygen tension measurements in the preretinal vitreous in cats.