Evaluation of the Tono-Pen 2 and the X-Pert noncontact tonometers in cataract surgery.

The Oculab Tono-Pen and the X-Pert noncontact tonometers (NCTs) were compared to the Goldmann applanation tonometer in a consecutive series of 45 patients before and after cataract surgery. In the preoperative period, the mean value of the paired difference at intraocular pressure (IOP) measurements was -1.30 +/- 2.11 mm Hg (mean +/- SD) for the X-Pert NCT (X-Pert NCT minus Goldmann) and -0.19 +/- 2.56 mm Hg for the Tono-Pen 2 (Tono-Pen 2 minus Goldmann). In the postoperative period, this mean difference was 0.26 +/- 2.45 mm Hg for the X-Pert NCT and 0.87 +/- 2.83 mm Hg for the Tono-Pen 2. We found 87 and 67% of the X-Pert NCT and the Tono-Pen 2 readings to be within +/- 2 mm Hg of the Goldmann readings, respectively. In both preoperative and postoperative eyes, correlation coefficients between the readings of the three instruments were high (ranging from 0.84 to 0.96). Differences between the three tonometers were not correlated with corneal thickness of corneal curvature postoperatively. Both Tono-Pen 2 and X-Pert NCT could thus be considered accurate instruments for IOP screening after cataract surgery when compared to the Goldmann applanation tonometer.