Abstract
Purpose:
To develop and test a method to measure oxygen saturation of extravasated hemoglobin in retinal tissue in disorders such as central retinal vein occlusion (CRVO).
Methods:
The spectrophotometric retinal oximeter (Oxymap ehf, Reykjavik, Iceland) simultaneously delivers two monochromatic images of the same area of the fundus, one which is is sensitive to oxygen saturation (600nm) and one which is not (570nm). The light absorbance of retinal hemorrhages was measured at these two wavelengths in 7 CRVO patients. The light absorbance was used to estimate oxygen saturation in the hemorrhages. Variability between measurements of areas within the same retinal hemorrhage was determined. The mean oxygen saturation in retinal vessels was measured with automated software.
Results:
The mean saturation in the retinal hemorrhages was 58±18% (mean±SD, n=7). The mean saturation in retinal venules in the same patients was 33±14% (p=0.03). Standard deviation between repeated measurements on the same hemorrhage in the same image was 14.6% (saturation percentage).
Conclusions:
The results suggest that measurement of oxygen saturation of extravascular hemoglobin in retinal tissues is possible. Saturation values in hemorrhages are between saturation values in arterioles and venules. The oxygen saturation can be correlated to PO2 and therefore might be an indicator of the oxygenation of the tissue.
Keywords: 635 oxygen •
688 retina •
551 imaging/image analysis: non-clinical