The Choroidal Eye Oximeter: An Instrument for Measuring Oxygen Saturation of Choroidal Blood In Vivo

The Choroidal Eye Oximeter is an electro-optical instrument that non-invasively measures the oxygen saturation of choroidal blood in the back of the human eye by a spectrophotometric method. Since choroidal blood is characteristic of blood which is supplied to the brain, the Choroidal Eye Oximeter is essentially using the eye as a ``window´´ to look into the brain. The instrument can thus be used to monitor the amount of oxygen which is supplied to the brain under varying external conditions. The instrument consists of two basic systems: the Optical System and the Electronic System. The Optical System produces a suitable bi-chromatic beam of light, reflects this beam from the fundus of the subject´s eye, and onto a low-noise photodetector. The Electronic System amplifies the weak composite signal from the photodetector, separates the two spectral components, computes the average oxygen saturation from the area of the fundus that was sampled, and displays the value of the computed oxygen saturation on a panel meter. The instrument may be used with a chart recorder to continuously record the kinetic changes of either the oxygen saturation or the fundus reflectivity at each of the two measuring wavelengths.