Instrument for the measurement of retinal vessel oxygen saturation

Retinal vessel oxygen saturation has been suggested as a parameter for monitoring a wide range of conditions including occult blood loss and a variety of ophthalmic diseases. We have developed an Eye Oximeter (EOX), that noninvasively measures the oxygen saturation of the blood in individual large retinal vessels using scanning lasers. One-dimensional vessel extinction profiles are obtained at four wavelengths (629, 678, 821 and 899 nm), and the vessel transmittances computed. The oxygen saturation of blood within the vessel is then calculated from the transmittance data. We have performed an in vitro experiment on human blood which demonstrates the calibration of the EOX measurement and validates our oximetry equations. Retinal vessel oxygen saturation was measured in a human subject and found to be 65%O₂Sat and 101-102%O₂Sat in the veins and arteries on the optic disk. Irregularities in the background measured away from the optic disk resulted in a larger variance in the calculated saturation when compared to measurements made on the disk.