Dynamics of Intravitreal Sulfur Hexafluoride Gas

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Abstract

Sulfur hexafluoride gas (SF₆) has recently been used as an adjunct in the treatment of retinal detachments. In order to determine the change in gas volume and concentration with time following injection of SF₆ into the vitreous cavity, vitreous was aspirated from the rabbit eye and replaced by 100 per cent SF₆. At various time intervals (6, 24, 48, 72, and 96 hours) the gas was aspirated into a syringe, the volume measured, and the sample analyzed with a gas chromatograph for per cent volume concentration of SF₆, N₂, O₂, CO₂. The gas pocket expanded to its maximum volume at 24 hours with a dry concentration of 18.3 per cent SF₆, 71.5 per cent N₂, 4.7 per cent O₂, and 5.5 per cent CO₂. The volume then decreased exponentially reaching the original volume at 96 hours, and the pocket was absorbed in 8 to 10 days. The concentration of O₂ and CO₂ remained stable from 6 to 96 hours, while the concentration of N₂ increased as the concentration of SF₆ decreased. The time for persistence of the gas pocket was related to the initial volume of SF₆ injected.