Abstract
Abstract: :
Purpose: To determine the ability of the avascular region of the rabbit retina to regulate choroidal and intraretinal oxygen levels during periods of acute systemic hyperoxia and to monitor any changes in retinal oxygen consumption. Methods: Oxygen sensitive microelectrodes were used to measure oxygen tension as a function of depth through the retina and choroid in anaesthetized rabbits (n=6) before and after stepwise increments in systemic arterial oxygen level. The extent of any oxygen rises throughout the retina and choroid was determined and inner and outer retinal oxygen consumption was quantified by analyzing the intraretinal oxygen distribution. Results: Increases in systemic arterial oxygen in the rabbit results in significant increases in oxygen tension in the choroid and in all retinal layers. There is no apparent regulation of choroidal oxygen tension as previously seen in the avascular retina of the guinea pig. Neither is there any evidence of increases in oxygen consumption within the retina, which has been shown to dampen the extent of raised oxygen levels on the inner retina in other mammals. Consequently, all retinal layers in the avascular area of the rabbit retina are exposed higher oxygen levels during systemic hyperoxia than have been reported in other species. Conclusions: Unlike other mammals studied to date, the rabbit does not seem to possess any regulatory mechanisms for controlling the intraretinal oxygen environment during acute changes in systemic arterial oxygen levels. This may well account for the reported vulnerability of the rabbit retina to toxic damage during extended periods of systemic hyperoxia.
Keywords: retina • metabolism