Effect of recipient corneal pathology on Pascal tonometer and Goldmann tonometer readings in eyes after penetrating keratoplasty.

PURPOSE: To assess the influence of recipient corneal pathology on the performance of the Pascal dynamic contour tonometer (PDCT) (Swiss Microtechnology AG) by comparing it to Goldmann applanation tonometry (GAT) in post-penetrating keratoplasty (PKP) eyes. METHODS: Intraocular pressure (IOP) was measured in 40 post-PKP eyes of 40 patients using PDCT and GAT. The study patients were divided into two groups. Group A included patients who had undergone PKP for ectatic corneal disorders (keratoconus, n=20) and group B included patients who had undergone PKP for other non-ectatic corneal disorders (Fuchs, post-corneal ulcer, post-chemical burn,post-trauma, n=20). Keratometric measurements were obtained in all eyes using Orbscan II (Bausch &Lomb) and central corneal thickness (CCT) was measured using Corneo-Gaze Plus (Sonogaze). RESULTS: In group B, a correlation between PDCT and GAT IOP measurements was observed. In group A, GAT IOP measurements were significantly lower than PDCT measurements (3.7 +/- 1.8 mmHg,p<0.001). Additionally, CCT affected GAT IOP measurements much more than PDCT measurements,while corneal curvature did not significantly affect IOP measurements of any instrument in either group. CONCLUSIONS: In post-PKP eyes, PDCT appears to be less influenced than GAT by CCT and pre-existing recipient corneal pathology. Therefore, PDCT may be better suited for monitoring IOP in post-PKP eyes.

Assessment of the pascal dynamic contour tonometer in measuring intraocular pressure in keratoconic eyes.

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) in keratoconic eyes. METHODS: Intraocular pressure (IOP) was measured in both eyes of 32 patients with keratoconus using PDCT, GAT, and NCT. IOP measurements were also obtained with all 3 instruments in 46 patients with healthy eyes in the same age range, which served as controls. Keratometric measurements were obtained in all eyes using Orbscan II (Bausch & Lomb) and central corneal thickness was measured using Corneo-gaze plus (Sonogaze). RESULTS: In the control group, a correlation between PDCT, GAT, and NCT IOP measurements was observed. In keratoconic eyes, GAT and NCT IOP measurements were significantly lower than PDCT measurements (5.3+/-2.2 mm Hg and 4.75+/-1.7 mm Hg, respectively). Unlike GAT and NCT, PDCT measurements in both groups were not significantly affected by central corneal thickness. Additionally, the mean IOP measurement in the keratoconic eyes was lower than that of the control group, particularly when measured with GAT and NCT. Corneal curvature, did not significantly affect IOP measurements of any instrument in either group. CONCLUSIONS: The corneal abnormalities characteristical of keratoconus seem to influence more GAT and NCT IOP measurements than PDCT IOP measurements. Therefore, PDCT may be better suited for monitoring IOP in keratoconic eyes.

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

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 microm (median 78 microm). 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.