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. Oxygensensitive microelectrodes were used to measure vitreal PO 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 PO (mid vitreous PO of 22·6±1·9 mmHg (±s.e.; n = 6), except for a layer about 200 μm thick at the retinal surface where significant PO gradients exist, especially in the region of retinal arteries. Midvitreous PO is similar to the PO at retinal veins. All vitreal PO values increase if ventilatory oxygen is raised to 100% O2. After equilibration, the main body of the vitreous again has an almost constant PO, a factor of 3·75 ± 0·40 (n = 10), higher than for 20% O2 ventilation except for a region about 400 μm thick adjacent to the internal limiting membrane where the local geometry of the retinal circulation dictates PO distribution. When the electrode was oriented to make contact with the retina at different distances from the optic disk, venous PO 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. © 1991.