Mackay-Marg tonometry over therapeutic soft contact lenses

We evaluated the accuracy of Mackay-Marg electronic applanation tonometry over Bausch and Lomb Plano-T therapeutic soft contact lenses on eye bank, postoperative keratoplasty, and normal eyes. Intraocular pressure (IOP) measurements were compared in the same eye without and with the lens in place. The mean difference of IOP readings through the lens was not statistically different from that without the lens over an IOP range of 10 through 50 mm Hg. We constructed confidence intervals to predict the accuracy of future observations. Results revealed that with 95% confidence, the range of difference between IOP readings without and with the lens in place was from -4.7 to +3.6 mm Hg in eye bank eyes, from -4.3 to +7.4 mm Hg in postoperative penetrating keratoplasty patients, and from -3.5 to +7.4 mm Hg in postoperative lamellar keratoplasty patients, from -3.3 to +2.7 mm Hg in normal eyes. We concluded that IOP can be measured with the Mackay-Marg tonometer through a therapeutic soft contact lens over a corneal graft. Although the readings are not as accurate as without the lens, they are probably adequate as a guide to the necessity of treating increased IOP in postoperative keratoplasty patients.