Uveal Extraction and Clearance of Oxygen in Normal, Inflammed and Hyperthermic Eyes

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Abstract
Isolated eyes during whole blood homoperfusion, wherein both uveal and retinal effluents were sampled, showed an approximate 80% rise in O2 extraction over in vivo studies based upon sampling of the anterior ciliary vein. Uveoretinal responses to disease and therapy may be examined by the isolated homoperfusion, while uveal changes excluding retina are expressed better by in vivo sampling of the anterior ciliary vein. Certain information on uveal respiration and plasma flow may be gotten by measurements of O2 clearance if at steady state full hemoglobin saturation and attainment of high extraction ratio can be assured by breathing pure O2. This has a certain advantage of minimal ocular trauma, since it does not require recovery of ocular venous samples. Uveoretinal responses to stress in isolated homoperfusion show greater heat sensitivity and less inflammatory suppression than do eyes studied by in vivo sampling of the anterior ciliary vein; this likely relates to high QO2 [O2 quotient] of the retina. Aqueous flow measurements in connection with clearance studies may be made using 1-125 hippuric-acid tracer injected into the anterior chamber in low volume (1-2 mm3) with exponential changes in radioactivity measured by a scintillation probe applied to the corneal surface.