Blood Flow and Oxygen Extraction in the Cat Uvea at Normal and High Intraocular Pressures

Publisher Website
Google Scholar
Abstract
The rate of blood flow through the uvea and the arterio‐venous O2difference across the uveal tract were determined in cats. The normal rate of blood flow was 1.14 ± 0.23 ml/min and the normal a‐v O2difference was 1.02 ± 0.16 volume per cent. The O2extraction was 8.0 ± 0.6 μl NTP/min. The arterial O2saturation, Po2, Pco2, and pH were 95.6 ± 0.3 per cent, 93 ± 3 mm Hg, 25.8 ± 1.0 mm Hg, and 7.44 ± 0.01 units, respectively. An artificial rise in eye pressure reduced the rate of uveal blood flow and increased the a‐v O2difference. The O2extraction was relatively constant at blood flow rates above 0.3–0.5 ml/min. At lower flow rates the O2extraction decreased in spite of a high venous O2concentration. Blood collected from the choroidal veins had a slightly higher O2concentration than blood collected from the intrascleral venous plexus. A reduction in uveal blood flow, produced by a reduction in the mean arterial blood pressure, reduced the O2content both in blood collected from the choroid and in blood leaving the anterior uvea. The results suggest that at low perfusion pressures there is anoxia in some tissue supplied by the uveal vessels, in spite of a relatively well oxygenated venous blood.