Hyperoxia promotes electroretinogram recovery after retinal artery occlusion in cats

PURPOSE. This work assessed the hypotheses that ( 1) hyperoxia is preferable to air breathing during retinal arterial occlusion, ( 2) hyperoxia during occlusion is beneficial in promoting recovery from arterial occlusion, and ( 3) hyperoxia has value even if it is delayed relative to the onset of the occlusion. METHODS. Reversible branch retinal artery occlusion was produced by pressing with a glass probe onto an artery emerging from the superior part of the optic disc in the retina of anesthetized cats. During 2-hour occlusion episodes, the cats breathed 100% O-2, 1 hour of air and 1 hour of 100% O-2, 1 hour of air and 1 hour of 70% O-2, or air. Intraretinal ERGs were recorded before, during, and after the occlusion. RESULTS. Hyperoxia during occlusion preserved intraretinal b-wave amplitude at 86% +/- 12% of normal; longer durations of increased oxygenation maintained the b-wave at higher levels during occlusion and increased the probability of b-wave recovery after occlusion; higher O-2\ content in the breathing gas increased b-wave amplitude during recovery; and hyperoxia during occlusion decreased the time it took for the b-wave to recover after the occlusion. CONCLUSIONS. Hyperoxia is preferable to air breathing during retinal arterial occlusion not only for maintaining b-wave amplitude during occlusion, but also for providing a shorter recovery time and better percentage recovery after the end of the occlusion. Even if it is not possible to begin hyperoxia at the onset of occlusion, it may still be valuable.