Method comparison of two non-invasive dual-wavelength spectrophotometric retinal oximeters in healthy young subjects during normoxia

PurposeSpectrophotometric retinal oximetry is a non-invasive technology for measuring oxygen saturation in arterioles and venules (SaO(2), SvO(2)). We compared two commercially available systems: the Oxymap T1 (Oxymap ehf., Reykjavik, Iceland) and the Dynamic Vessel Analyzer (DVA, Imedos, Jena, Germany). MethodsTwenty healthy adults were included after giving informed consent. Two measurement cycles 30min apart, including Oxymap T1, DVA, arterialized capillary blood draw of the earlobe (ScO2) and peripheral oxygen saturation using finger pulse oximetry (SpO(2)) were scheduled. ResultsSaO(2) (p>0.0004) but not SvO(2) (p<0.05) was statistically significantly different between the retinal oximeters used. Agreement between devices using repeated SO2 measurements resulted in a standard deviation (SD) of differences of 3.5% in retinal arterioles and 4.8% in venules. Bland-Altman plot using the mean of a participant's two measurements from each device showed an average mean difference of 4.4% (95% confidence limits of agreement: -8.6 to 17.4) and -3.3% (95% confidence limits of agreement: -28.8 to 22.2) for SaO(2) and SvO(2), respectively. Comparison of mean SaO(2) and SvO(2) with mean ScO2 and SpO(2) indicated that SO2 measurements were generally higher in ScO2 and SpO(2). ConclusionThis study shows very good repeatability for both devices, which is consistent with the literature. However, it does not show sufficient concordance between SaO(2) measurements from both devices, indicating that patients should be followed by one device only. Differences in absorbance wavelengths used and image post-processing may explain the differences.