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Maria S. Gottfredsdottir, Halldor R. Bergvinsson, Renata Blondal, Sveinn H. Hardarson, Jona V. Kristjansdottir, Einar Stefánsson; Retinal Oxygen Saturation Measurements: Repeatability And Influence Of Vessel Diameter. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5668.
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(1) To test whether retinal vessel oxygen saturation measurements are affected by vessel diameter. (2) To test the repeatability of oxygen saturation measurements.
Fundus images of 12 healthy individuals were obtained with a fundus camera based retinal oximeter (Oxymap ehf., Reykjavík, Iceland). Specialized software, Oxymap Analyzer, analyzed the images and measured the oxygen saturation and vessel diameter. (1) Oxygen saturation was measured in first and second degree vessels (parent and daughter vessels) and the results compared. (2) Oxygen saturation was measured twice in the same vessel segment and the standard deviation between the measurements calculated (ANOVA).
(1) Oxygen saturation in first degree arteriole divided by oxygen saturation in second degree arterioles gave the result 0.97±0.02 (n=12, mean ± SD). The corresponding ratio for venules was 0.90±0.04. Both ratios are significantly different from 1.00 (p<0.001). (2) The standard deviation between repeated measurements was 1.5% and 3.5% for first degree arterioles and venules, respectively. The corresponding value was 0.9% for second degree arterioles and 4.3% for second degree venules.
(1) Oxygen saturation measurements depend on the vessel diameter where narrower vessels show higher oxygen saturation. This agrees with previous reports by Beach et al. and Hammer et al. The data allows this offset to be corrected. (2) Oxygen saturation measurements in first and second degree vessels show good repeatability.
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