The iCare rebound tonometer: comparisons with Goldmann tonometry, and influence of central corneal thickness

P>Purpose: To assess agreement between the iCare rebound tonometer and Goldmann tonometry and to assess the influence of central corneal thickness and the value of scleral rebound tonometer readings. Methods: Prospective single-centre cross-sectional study comparing iCare rebound tonometer (RT) intraocular pressure (IOP) readings taken from corneal and scleral locations to Goldmann applanation tonometer (GAT) readings in 100 subjects attending ophthalmology clinics. Results: There was a significant difference between RT and GAT, with RT tending to overestimate IOP. The mean difference between RT and GAT measurements was 3.36 mmHg. The mean difference between the log of RT and the log of GAT measurements was 0.2356, a ratio of 1.27 (P < 0.0001). A formula derived from a linear regression analysis suggested that a 10% increase in CCT increased the RT IOP reading by 9.9%. Scleral RT readings showed no relationship to GAT readings. Conclusions: The rebound tonometer cannot replace the Goldmann tonometer in the office setting given the wide limits of agreement between the two devices. Corneal rebound tonometer readings are influenced by CCT whereas scleral rebound tonometer readings are of no value.