Aspects of oxygen and glucose consumption in the retina: effects of high intraocular pressure and light.

Studies on retinal oxygen and glucose consumption in cats and pigs are reviewed and recent experiments with the deoxyglucose method in monkeys are described. In all three species, the retina is supplied with nutrients by both the retinal and the choroidal blood vessels. Studies on regional blood flow and differences in arteriovenous concentration in cats have indicated that under conditions of general anesthesia and exposure to laboratory light, the oxygen supply from the choroid is about 5.6 microliters/min and that from the retinal vessels, 1.3 microliters/min. In pigs the corresponding figures were about 4 and 2.9 microliters/min, respectively. Moderate reductions in perfusion pressure caused by increments in intraocular pressure or reductions in arterial blood pressure resulted in little change in oxygen tension in the inner retina, due to efficient autoregulation of retinal blood flow. Reduced choroidal blood flow was to a large extent compensated by increased differences in arteriovenous concentration. Studies using the deoxyglucose method in monkeys indicated that pentobarbital anesthesia and constant illumination tend to reduce the metabolism of the retina. In darkness, glucose consumption in the photoreceptors was higher than that recorded under conditions of constant illumination with white light. Flickering light at 4 Hz enhanced glucose consumption in the inner retina. At very high intraocular pressures glucose consumption in the retina was enhanced, probably as a result of partial ischemia, with a shift to more anaerobic glucose metabolism.