Vitreal oxygen tension measurements in the rat eye

Oxygen tension measurements are presented for the first time for the vitreous body of the rat eye. Oxygen-sensitive microelectrodes were used to measure vitreal PO2 profiles for two breathing conditions: 20 and 100% O2. Results show that for ventilation with 20% O2 most of the vitreous body has a constant PO2 (mid vitreous PO2 of 22.6 +/- 1.9 mmHg (+/- S.E.; n = 6), except for a layer about 200 microns thick at the retinal surface where significant PO2 gradients exist, especially in the region of retinal arteries. Midvitreous PO2 is similar to the PO2 at retinal veins. All vitreal PO2 values increase if ventilatory oxygen is raised to 100% O2. After equilibration, the main body of the vitreous again has an almost constant PO2, a factor of 3.75 +/- 0.40 (n = 10), higher than for 20% O2 ventilation except for a region about 400 microns thick adjacent to the internal limiting membrane where the local geometry of the retinal circulation dictates PO2 distribution. When the electrode was oriented to make contact with the retina at different distances from the optic disk, venous PO2 was observed to decrease in more peripheral locations. This work opens the possibility of investigating the role of hypoxia in rat models of retinal vascular disease.