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

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.

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).

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.

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.