Validity and Limits of the Rebound Tonometer (ICare®): Clinical Study

Abstract

Purpose The aim of this study was to evaluate the measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare®) compared with Goldmann applanation tonometry (GAT). We also aimed to quantify the systematic and random errors (bias) of the 2 methods, to evaluate the sensitivity and specificity of the ICare® tonometer in identifying patients with 21 mmHg or more measured with the GAT, and to study the influence of corneal thickness on IOP measurement with the 2 tonometers. Methods We compared the IOP values obtained with the 2 instruments in 97 patients. Results Analysis based on the Bland and Altman method revealed that the IOP values recorded with the ICare® tonometer were slightly higher than those obtained with the GAT. The estimated bias for right eye measurements was 0.78 mmHg with 95% limits of agreement ±3.55 mmHg. This overestimation, which is not clinically relevant, was confirmed when we used the IOP values corrected according to central corneal thickness for data analysis. The sensitivity and specificity were 0.90 and 0.95, respectively. Conclusions The ICare® tonometer proved to be comparable with other nonconventional tonometers and can be used by nonophthalmologists and paramedical personnel during screening tests of populations. In addition, the ICare® tonometer could be considered a valid alternative to GAT when GAT is not available.