Air travel with intraocular gas. I. The mechanisms for compensation.

The absolute intraocular pressure of the gas-containing eye of a rabbit fell with the fall in cabin pressure during a simulated airplane ascent but lagged behind. The lag was manifested clinically as a relative rise in transscleral pressure. The amount of lag depended on the amount of gas in the eye at takeoff. As there is no significant transfer of gas out of the eye during the ascent, the fall in absolute intraocular pressure could only be mediated by expansion of the bubble. The enabling mechanisms for expansion are choroidal compression, scleral expansion, and accelerated aqueous outflow.