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Thorunn Scheving Eliasdottir, David Bragason, Sveinn Hakon Hardarson, Jona Valgerdur Kristjansdottir, Enchtuja B. Suchegin, Anna Einarsdottir, Einar Stefansson; Retinal oximetry in patients with carotid stenosis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4420.
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Carotid stenosis may affect ocular perfusion. The purpose of this study was to estimate the effects of severe carotid artery stenosis and oxygen therapy on oxygen saturation in retinal vessels.
<br /> The spectrophotometric retinal oximeter (Oxymap T1, Oxymap ehf., Reykjavik, Iceland) is based on a fundus camera and analysis software. It simultaneously captures images of retinal vessels at 570nm and 600nm wavelengths for calculation of hemoglobin oxygen saturation. Six patients with ≥ 70% carotid stenosis were included in the study. Two patients had bilateral carotid stenosis and four unilateral. Brachial blood pressure, finger pulse oximetry, respiratory rate, concentration of inhaled oxygen and end-tidal carbon dioxide were monitored throughout the study. Oxygen saturation in retinal arterioles and venules of both eyes was measured with ambient air and supplemental oxygen (3L/min) breathing. Oxygen saturation of retinal vessels was compared with six age- and gender matched healthy controls from our database.
In eyes on the carotid stenosis side, oxygen saturation during ambient air breathing was 92±4% in arterioles (mean ± standard deviation) and 93±2% in healthy controls (p=0.78, n=6, unpaired t-test). In venules the oxygen saturation was 57±4% compared with 55±4% in healthy controls (p=0.34). During ambient air breathing, oxygen saturation in retinal arterioles of the ipsilateral eye was 90±3% compared with 91±6% in the fellow eye (p=0.54,n=4, paired t-test). In retinal venules oxygen saturation was 56±3% in the eye on the carotid stenosis side compared with 56±8% in the fellow eye (p=0.99). The arteriovenous difference of both eyes was 35±2% (p=0.78) and did not significantly change during oxygen breathing (p=0.78 and 0.51). Oxygen saturation in retinal arterioles increased from 92±4% to 95±5% during oxygen breathing (p=0.007, n=6,paired t-test) and from 57±4% to 58±4% in venules (p=0.6). Finger pulse oximeter was 96±1% and 98±1% respectively during ambient air and oxygen breathing (p=0.002,n=6,paired-t-test).
No difference was found in retinal oxygen saturation in eyes on the same side as severe carotid stenosis. The arteriovenous difference is unaltered by the disease, indicating sufficient oxygen delivery to meet metabolic demand of the retinal tissue. Oxygen saturation in retinal arterioles and finger is significantly increased during oxygen breathing.
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