The retinal oxygen profile in cats.

This study records for the first time the retinal tissue oxygen partial pressure as a function of location within the retina of the domestic cat. Tissue pO2 was recorded with oxygen sensitive microelectrodes that use the polarographic principle. The mean vitreal pO2 close to the internal limiting membrane was 20.2 +/- 2.3 mmHg. The internal limiting membrane does not act as a diffusion barrier for oxygen. As the electrode was advanced into the inner retina, the tissue pO2 rose gradually to a value of 24.6 +/- 2.3 mmHg and then fell to a minimum of 12.0 +/- 5.5 mmHg before rising again to a value of 29.2 +/- 2.5 mmHg. Further insertion resulted in a sudden steep rise of tissue pO2 values to 72.0 +/- 5.1 mmHg, after which there was no further alteration in measured values. Although the exact location within the retina of the recording electrode was not known, it is probable that the tissue pO2 minimum occurs at about the level of the inner nuclear layer. Therefore, it is probable that the retinal avascular layers receive their oxygen supply primarily from the choroidal circulation in the cat.