The effect of the retinal circulation on vitreal oxygen tension

Publisher Website
Google Scholar
Abstract
Detailed measurements have been made of the preretinal partial pressure of O2 (PO2) in the cat eye to determine the effect of the local geometry of the retinal circulation on vitreal PO2 values. Measurements were made with O2 sensitive microelectrodes for 2 ventilation conditions: air and 100% O2 breathing. PO2 gradients, which may extend as far as 800 .mu.m from the internal limiting membrane, were shown to exist in the vicinity of retinal arteries. Close to a retinal vein there is either a very shallow PO2 gradient or none at all. Coarse vitreal PO2 profiles which were measured out to the midvitreous show that the gradients are very shallow to within 1 mm of the retina. The close agreement between midvitreous PO2 and retinal venous PO2 implies that the retinal venous PO2 sets the PO2 value of the main bulk of the vitreous. Absolute PO2 values indicate that the retinal arterial walls offer easy diffusion for oxygen, and that at 100% O2 breathing almost all the oxygen offloaded from the retinal circulation is from dissolved oxygen. Alterations in the physiological condition of the eye such as those due to changes in the ventilation gas, blood pressure or intraocular pressure may cause relative movement between the microelectrode and the retina. This movement can lead to apparent changes in vitreal PO2 when it occurs in a region in which substantial PO2 gradients exist.