Reproducibility of retinal oximetry measurements in healthy and diseased retinas

Purpose: Retinal oximetry (RO) has been established as a non-invasive method to analyse oxygen saturation in retinal vessels. The aim of our study was to determine the reproducibility of RO images in healthy and in diseased retinas. Methods: A total of 61 right eyes (244 RO images) in 61 subjects (35 $, 26 #) were examined: 22 controls, 18 patients with glaucoma and 21 patients with inherited retinal diseases (IRDs). Four test –retest RO images were obtained in each subject. Oxygen saturation was measured with the oxygen saturation measurement tool of the Retinal Vessel Analyser (RVA; IMEDOS Systems UG, Jena, Germany). The test –retest standard deviation within the subject’s ( ! SD w) measurements (the mean vessel oxygen saturation in retinal venules and arterioles), its coefficient of variation (CoV) and the intraclass correlation coefficients (ICC) were analysed. Results: The average test –retest SD w in venules was ! 2.52% (CoV = 4.35%) and in arterioles was ! 1.67% (CoV = 1.76%). Among controls, glaucoma eyes and eyes with IRDs, the test –retest SD w in venules were ! 2.33% (CoV = 4.48%), ! 2.85% (CoV = 4.71%) and ! 2.43% (CoV = 3.90%) (SD w p = 0.366 (CoV p = 0.452); one-way ANOVA ). The test –retest SD w in arterioles were ! 1.65% (CoV = 1.80%), ! 1.83% (CoV = 1.92%) and ! 1.54% (CoV = 1.56%), respectively [SD w p = 0.762 (CoV p = 0.686)]. The ICCs in venules were 0.76 in controls, 0.69 in patients with glaucoma and 0.82 in patients with IRD. The ICCs in arterioles were, respectively, 0.92, 0.70 and 0.93. Conclusion: The reproducibility of RO in healthy, as well as in diseased retinas, is excellent. In the glaucoma group, the lower standard deviation between subjects (SD b) for arterioles contributes to the lower ICCs. Nevertheless, the measurements of oxygen saturation in arterioles seem more reliable when compared to venules.