A clinical comparison of the Xpert non-contact tonometer with the Goldmannapplanation tonometer after penetrating keratoplasty

Purpose: To assess the agreement between the Xpert non-contact tonometer (N CT) and the Goldmann applanation tonometer in patients who have undergone p enetrating keratoplasty, Methods: The study material consisted of 42 consecutive patients (43 eyes) who had undergone penetrating keratoplasty within the previous 13 months. Results: The slope of the linear relationship between the two measurement m ethods did not differ significantly from 1.0. The mean difference between t he methods of 0.96 mmHg was not statistically significant. The range of int raindividual differences between the methods was from -9.8 to 22.8 mmHg. Th e standard deviation of differences was 6.62 mmHg. The 95% limits of agreem ent were -12.00 to 13.94 mmHg. There was no significant correlation between the central corneal thickness, astigmatism or transplant size and the diff erence between the methods. Conclusion: The Xpert NCT shows considerable variation from the Goldmann va lues. The degree of agreement with the true IOP value remains to be shown.