Clinical evaluation of the Canon TX-10 noncontact tonometer in healthy eyes

Abstract

To assess the accuracy and repeatability of intraocular pressure (IOP) measurements obtained with the Canon TX-10 noncontact tonometer (NCT), using the Goldmann applanation tonometer (GAT) as the gold standard. Seventy-three young healthy subjects were enrolled in the study. Central corneal thickness (CCT) was obtained with Orbscan Topography System and then repeated IOP measurements were obtained with both tonometers. Canon TX-10 NCT was performed first, followed by GAT. Another study sample of 32 young healthy subjects was used to test the repeatability with both tonometers. Two sets of data were acquired separated by 1 week. Plotting the difference between the methods against the mean was done to compare the tonometers and the intersession variability. The hypothesis of zero bias was examined by a paired t test. The 95% limits of agreement (LoA) were also calculated. No statistically significant differences were found when comparing the Canon TX-10 NCT with GAT, displaying close level of agreement with GAT as seen by the 95% LoA (-4.78 mmHg to +4.00 mmHg). CCT ranged from 419 microm to 585 microm and no relationship was found between CCT and IOP measurements. The coefficients of repeatability were 3.70 mmHg and 3.41 mmHg for GAT and TX-10 tonometers, respectively. There was a good agreement between Canon TX-10 and GAT in healthy subjects. From the results obtained here, CCT appears to not affect IOP measurements when CCT is thinner than 570 microm.