Comparison of the new rebound tonometer with Goldmann applanation tonometer in a clinical setting

Purpose: To evaluate the clinical usefulness of a new rebound tonometer, Icare((R)) PRO (Icare PRO), by comparison with Goldmann applanation tonometry (GAT) in a study on patients with glaucoma. Methods: One hundred and seventy-two eyes of 86 subjects were enrolled in this study. All of the subjects were examined with an autorefractometer, Icare PRO, slit-lamp biomicroscope, GAT, ultrasound A-scan and pachymeter. Three intraocular pressure (IOP) measurements were obtained by Icare PRO and GAT. The intraobserver reliabilities were established by calculating the intraclass correlation coefficients. The Bland-Altman plot was used to compare the Icare PRO and GAT. Results: There was a good correlation between the IOP measurement by GAT and that by Icare PRO (r=0.6995, p<0.001). The intraclass correlation coefficients of Icare PRO and GAT were 0.778 and 0.955, respectively. The IOP differences between Icare PRO and GAT (mean: 1.92mmHg; SD: 3.29mmHg; 95% limit of agreement: -4.52 to 8.37mmHg) did not vary over the wide range of central corneal thickness (p=0.498), age (p=0.248), axial length (p=0.277) or spherical equivalent (p=0.075). Conclusions: Although IOP with Icare PRO was higher than that with GAT, especially at lower GAT IOP value, Icare PRO was found to be a reliable method and showed a good correlation with GAT. The IOP difference between Icare PRO and GAT was not affected by the central corneal thickness, age, axial length or spherical equivalent. Icare PRO can be expected not only to be a good screening tool but also to be a good substitute for GAT.