Qualitative fundus oximetry in the albino rabbit's eye

The principle of fundus oximetry, as used by Broadfoot, Gloster and Greaves (1961), has been modified and elaborated, using two monochromatic light bundles, one with minimal, the other with maximal difference in the extinction coefficient for Hb and HbO₂, a high chopping frequency, fibre optics and a Lovac contact lens. Anaesthetized albino rabbits were used with the light entering the dilated pupil. The returning light can be divided into a non-variable part, originating from various planes of transition, and a part that behaves as if passed through a blood film of twice the vascular laye thickness. Using differential recording—the difference made zero at the beginning of the experiment—a higher sensitivity of the system may be employed than in the case of direct recording of the intensity of the returning light. Changes in oxygenation gave reproducible qualitative measurements of the oxygen saturation of the blood in the vascular layer.