Oxygen lowers intraocular pressure.

A significant decrease in intraocular pressure was demonstrated in 14 patients as atmospheric pressure was increased at intervals of 0.5 atmospheric pressure up to 3 atmospheres within a hyperbaric chamber. Nine of these patients had the identical protocol repeated in room air at atmospheric pressure without a significant change in intraocular pressure. Administration of 100% O2 at 15 L/min by partial rebreathing face mask to these patients using the same protocol at atmospheric pressure resulted in a significant decrease in intraocular pressure. The results in the oxygen and hyperbaric groups were not statistically different. While in the hyperbaric chamber, scleral rigidity increased uniformly, outflow facility decreased significantly, and keratometry readings remained unchanged. A significant decrease in intraocular prssure occurred in 20 rabbits that received 100% oxygen by partial rebreathing face mask for 180 minutes. Arterial blood gases were obtained at 0.90, and 180 min in seven rabbits. The pH and pCO2 did not change significantly; however, pO2 was markedly elevated. Increased oxygen concentration was felt to be responsible fot the decrease in intraocular pressure and the changes in other parameters observed in patients and rabbits.