Blood pO2 and blood flow at the optic disc

A fundus camera-based phosphorometer to noninvasively and quasicontinuously measure the blood partial pressure of oxygen (pO(2,blood)) in the microvasculature of the pig optic nerve using the principle of the phosphorescence quenching by O(2) is described. A porphyrin dye is injected into the venous circulation and the decay of its phosphorescence emission is detected locally in the eye, after excitation with a flash of light. Combined with blood flow measurements by means of a laser Doppler flowmeter mounted on the phosphorometer, we demonstrate the capability of the instrument to determine the time course of optic nerve blood flow and pO(2,blood) in response to various physiological stimuli, such as hyperoxia and hypercapnia. This instrument appears to be a useful tool for the investigation of the oxygenation of the optic nerve.