Effect of Carbogen (95% O₂/5% CO₂) on Retinal Oxygenation in Dark-Adapted Anesthetized Cats

Abstract

This work assessed the relative effects of inspiring carbogen (95% O₂/5% CO₂) and 100% O₂ on intraretinal PO₂ and oxygen consumption in the cat retina. Oxygen microelectrodes were used to measure the distribution of oxygen in the central retina of dark-adapted anesthetized cats during normoxia, 100% O2 breathing, and carbogen breathing. Profiles of oxygen tension (PO₂) as a function of retinal depth were recorded. Changes in PO₂ caused by the transient administration of carbogen and 100% oxygen were also measured at selected retinal depths. Average PO₂ values at the choroid, at the boundary between the inner and outer retina, and across the inner retina were significantly higher during inspiration of carbogen than 100% O₂. There were no significant differences among conditions in outer retinal oxygen consumption. During the transient gas administration, average changes in PO₂ generally increased with depth. At the end of gas administration, the decay of PO₂ within the retina occurred quickly, meaning that short-term gas administration may have little therapeutic value.

KEYWORDS:

• carbogen
• oxygen
• hyperoxia
• retina
• cat