The Oxygen Supply to the Retina, I. Effects of Changes in Intraocular and Arterial Blood Pressures, and in Arterial PO2 and Pco2 on the Oxygen Tension in the Vitreous Body of the Cat

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Abstract
The Po2 in the vitreous body close to the retina, PvrO2, was determined continuously with an O2 electrode. In cats with a mean arterial blood pressure of 176±7 cm H2O, a PaO2 of 98±2 mm Hg, a PaC02 of 27.0±1–2 mm Hg and a pH of 7.43±0.16 units the mean PVr02 was 18.9±1.5 mm Hg. Stepwise increments in the eye pressure had no effect on PVrO2 at perfusion pressures above 50–100 cm H2O. At lower perfusion pressures PvrO2 decreased. Changes in perfusion pressure caused by hemorrhage and retransfusion gave similar results. At low Paco2 levels PvrO2 decreased; at high PaCo2 levels values of 40–60 mm Hg were observed. Reductions in Pao2 decreased Pvro2, increments gave either no change or a rise in Pvr02‐ Hypercapnia combined with high Pao2 in several cases resulted in PVr02 values between 100 and 150 mm Hg. The results indicate that the blood flow through the retina is very efficiently autoregulated, that oxygen tends to induce vasoconstriction in the retinal blood vessels, that hypocapnia gives vasoconstriction and hypercapnia marked vasodilatation.