Measurement of Intraocular Pressure in Gas-filled Human Eye

ABSTRACT

The injection of various long-lasting inert gases into the vitreous cavity to flatten and support a detached retina is of proven value. Persistence of the inert gas can be advantageous from the point of view of retinal detachment surgery, but they can cause rising of the intraocular pressure(IOP) to a dangerously high level. So an accurate assessment of IOP in gas-filled eye is important. Previous studies documented that Schiotz tonometry significantly underestimates IOP in the gas-filled rabbit eye, and Goldmann tonometry is more accurate. But in the operating room, Schiotz tonometer is the only device to measure the IOP, so the relationship between the true lOP and the IOP measured by the Schiotz tonometry in the human eye is very important. In this study an attempt was made to find the extent of discrepancy between Schiotz and Goldmann tonometry in the assessment of IOP in the gas-filled human eye. We performed pars plana vitrectomy in 12 human eyes and pars plana vitrectomy with lensectomy in 10 human eyes. Postoperatively fluid-gas exchange was done with 15% perfluoropropane gas(C3F8). The IOP and gas level were checked immediately before fluid-gas exchange and 3hr, 6hr, 12hr, 24hr and 72hr after fluid-gas exchange using Schiotz and Goldmann tonometer. The relationship between IOP measured by Schiotz and Goldmann tonometer was suggested. In phakic and aphakic eyes, Schiotz tonometrry always gave a lower value, and the discrepancy seemed to be greater in the eyes filled with more gas.