Prediction of the kinetics of disappearance of sulfur hexafluoride and perfluoropropane intraocular gas bubbles.

Intravitreal gases are useful in treating complicated retinal detachments by providing internal tamponade of retinal breaks. The geometry of the intraocular gas bubble and the kinetics of intraocular gas absorption determine the geometry and duration of internal tamponade of the retinal break. The authors derived a mathematical relationship based on a geometric model of the rabbit eye which allows calculation of the volume of an intraocular gas bubble from its observed meniscus height. When compared with actual measured bubble volumes, this technique was found to provide an accurate, noninvasive method for determining true intraocular gas volumes. Using this model, the absorption of nonexpansile concentrations of sulfur hexafluoride (SF6) and perfluoropropane (C3F8) were found to obey first-order kinetics. Both gases were found to have an intraocular half-life two to three times shorter in aphakic rabbit eyes after total vitrectomy than in phakic rabbit eyes with intact vitreous.