The effect of intraocular pressure on the absorption of air from the vitreous cavity

Background: The duration of an intraocular gas bubble used in vitreoretinal surgery is an important determinant of the safety and effectiveness of intraocular gas use. Considerable variability impedes the clinical determination of this parameter. The aim of the study was to study experimentally the relationship between intraocular pressure (IOP) and the absorption of an intravitreal air bubble. Methods: We compared the rate of absorption of an intravitreal air bubble in rabbit eyes that had been treated with cyclocryotherapy (n = 17) to the absorption of air bubbles in untreated fellow eyes (n = 17). Results: Intravitreal air bubble persisted longer in the cyclocryotherapy-treated rabbit eye (mean ± SD 78 ± 16 h) than in the control fellow eyes (43 ± 15 h). This difference was statistically significant (P < 0.001). The length of time an air bubble persisted could be predicted from the IOP. Conclusions: The reason for the increased length of time an air bubble remained in cyclocryotherapy-treated eyes is probably the result of several factors, including primarily reduced aqueous flow and reduced IOP. Our results show that the duration of air injected into the vitreous cavity correlated to IOP. In addition to other known factors, the IOP should be considered in predicting intravitreal gas persistence.