Comparison between Pascal dynamic contour tonometer and Goldmann applanation tonometer after different types of refractive surgery

Abstract

To evaluate and compare the recorded IOP values of the Pascal dynamic contour tonometer (PDCT) and the Goldmann applanation tonometer (GAT) after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Three groups of 84, 182 and 43 patients each were treated by PRK for myopia, LASIK for myopia and LASIK for hyperopia respectively. Intraocular pressure (IOP) measurements were performed in all eyes 1 day before and 1, 3, 6 and 12 months after treatment with PDCT and GAT. Ultrasound pachymetry was performed in all eyes preoperatively and at 1st month postoperatively. Preoperatively and postoperatively, GAT readings were lower than PDCT in all groups (all p < 0.05). Postoperatively in the PRK group, compared to the preoperative value, the mean differences of IOP recorded with GAT at 1st, 3rd, 6th and 12th month were -1.4 mmHg, -1.7 mmHg, -1.7 mmHg and -1.9 mmHg respectively (all p < 0.05). In the myopic LASIK group; the corresponding values with GAT were -3.6 mmHg, -3.6 mmHg, -3.6 mmHg and -3.5 mmHg (all p < 0.05), while in the hyperopic LASIK group the corresponding values were -1.1 mmHg, -0.7 mmHg, -1.1 mmHg and -0.9 mmHg (all p < 0.05). The mean IOP difference (GAT-PDCT) for myopic PRK, myopic LASIK and hyperopic LASIK were respectively -3.8 mmHg, -4.1 mmHg and -1.5 mmHg at the 12-month follow-up. No statistically significant changes were found for any group with the PDCT. GAT-determined IOP values were significant lower at all time-points after hyperopic LASIK, as well as myopic PRK or LASIK. The Pascal tonometry values remained unaffected for all groups.