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TH Pham, D-UG Bartsch, WR Freeman; Retinal Vessel Reaction to 100% Oxygen and Carbogen Breathing in Diabetic Patients Using the Retinal Vessel Analyzer . Invest. Ophthalmol. Vis. Sci. 2002;43(13):559.
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Purpose:To study the retinal vascular diameter changes of diabetic patients treated with 100% oxygen or carbogen, a mixture of 95% oxygen and 5% carbon dioxide using the retinal vessel analyzer (RVA, IMEDOS GmbH, Weimar, Germany). Previous studies (Lanzl et al. Klin Monatsbl Augenheikd 2000 217(4): 231-5; Polak et al. Br J Ophthalmol 2000 84:1285-1290) have shown that the retinal vessel analyzer is an accurate system for the assessment of retinal diameters in healthy subjects. This study measures the retinal vasoconstriction induced by 100% oxygen and the retinal vasodilatation induced by carbogen in diabetic patients by continuous on-line measurement with the RVA. Methods:Continuous on-line measurement of retinal arterial and venous branch vessels was obtained in 15 diabetic volunteers. A baseline was taken during the first minute. Next, subjects were given 100% oxygen for 5 minutes by mask. Further recording ensued for 4 minutes while breathing room air. Subjects were then given carbogen by mask for 5 minutes. Vessel diameter change in percent to baseline was calculated for each individual and for a mean of the group. Results:With the RVA we were able to measure a reduction in retinal blood vessel diameter when breathing pure oxygen. In contrast, the retinal blood vessel diameter increased when breathing carbogen. The reaction of the vessel diameter was immediate, but gradual. Conclusion:The RVA allows measurement of real time retinal branch reactions. Retinal branch vessels are indicators for capillary perfusion. This study shows that diabetics lose part of their regulatory ability to either vasoconstrict when given oxygen and vasodilate when given carbogen.
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