Retinal Oxygen

Abstract

We reviewed research on retinal oxygen (O₂) distribution and use, focusing on O₂ microelectrode studies in animals with circulatory patterns similar to those of humans. The inner and outer halves of the retina are different domains in terms of O₂. Understanding their properties can suggest mechanisms of and therapies for retinal diseases. Inner retinal PO₂ averages about 20 mmHg. Effective O₂ autoregulation of the retinal circulation ensures that inner retinal PO₂ is relatively uninfluenced by systemic hypoxia and hyperoxia and increased intraocular pressure in healthy animals. Failures of the retinal circulation lead to tissue hypoxia that underlies the vasoproliferation in diabetic retinopathy and retinopathy of prematurity. Choroidal blood flow is not regulated metabolically, so systemic hypoxia and elevated intraocular pressure lead to decreases in choroidal PO₂ and photoreceptor O₂ consumption. The same lack of regulation allows choroidal PO₂ to increase dramatically during hyperoxia, offering the potential for O₂ to be used therapeutically in retinal vascular occlusive diseases and retinal detachment.