Assessment of the Pascal dynamic contour tonometer in monitoring intraocular pressure in unoperated eyes and eyes after LASIK

Abstract

Purpose: To assess the performance of the Pascal dynamic contour tonometer (PDCT) (Swiss Microtechnology AG) by comparing it to Goldmann applanation tonometry (GAT) and noncontact air tonometry (NCT) before and after laser in situ keratomileusis (LASIK). Setting: Vlemma Eye Institute, Athens, Greece. Methods: Intraocular pressure was measured in 118 eyes before and 1 and 4 weeks after LASIK using GAT, NCT, and the PDCT, which allows direct, digital, transcorneal measurement of intraocular pressure. Results: Preoperatively, central corneal thickness (CCT) correlated with GAT and NCT measurements but not with PDCT measurements. After LASIK, the mean reduction in CCT ranged from −3.0 to −171.0 μm (median 78 μm). The mean GAT measurement dropped by −4.9 mm Hg ± 2.7 (SD) at 1 week and was −5.4 ± 3.0 mm Hg at 4 weeks. Similar drops were observed in NCT measurements. The observed post-LASIK changes in GAT and NCT IOP measurements were not directly proportional to the change in CCT, refractive error, or mean keratometric readings. The preoperative and postoperative PDCT measurements did not differ significantly. Conclusions: The structural corneal changes induced by LASIK appeared to influence GAT and NCT measurements but not PDCT measurements. Therefore, PDCT may be better suited for monitoring IOP in unoperated eyes and in eyes that have had LASIK.