Anders Bill

Abstract A lm , A. and A. B ill . The oxygen supply to the retina, II. Effects of high intraocular pressure and of increased arterial carbon dioxide tension on uveal and retinal blood flow in cats. A study with radioactively labelled microspheres including flow determinations in brain and some other tissues. Acta physiol. scand. 1972. 84. 306–319. 15 μ and 35 μ microspheres labelled with 8S Sr and 169 Yb were used to determine the rate of blood flow through various intraocular tissues, optic nerve, brain, kidney cortex and small intestine in cats at normal and increased Paco2‐ One eye had its spontaneous intraocular pressure, the other eye had its pressure stabilized at a higher level. At normal P a co2 a reduction in perfusion pressure resulted in decreased vascular resistance in the iris, the ciliary body and the retina, but not in the choroid. In the retina the eye with reduced perfusion pressure had a significantly higher blood flow than the control eye. Increased PaCO 2 resulted in increased blood flow in all ocular tissues and all extraocular tissues studied except the kidney cortex. Reductions in perfusion pressure at high Paco 2 resulted in further decreases in vascular resistance in two eyes of seven only. The results suggest that about 21 % of the O 2 consumed by the retina is delivered by the retinal blood vessels, the rest by the choroid. Both myogenic and metabolic mechanisms seem to contribute to the adjustment of retinal vascular resistance after a change in perfusion pressure.