The utility of rebound tonometer in late elderly subjects

BACKGROUND To compare intraocular pressure (IOP) readings using the Icare rebound tonometer (RBT) versus the Goldmann applanation tonometer (GAT) in late elderly (aged 75 years or older) subjects with or without glaucoma, and to evaluate the influence of central corneal thickness (CCT) on IOP readings. METHODS The IOP measurements were obtained using the RBT and GAT, and CCT was measured using a specular-type microscope. Bland-Altman analysis was used to assess the clinical agreement between the two instruments. The influence of CCT adjusted for age on IOP readings was analyzed by multiple linear regression analysis. RESULTS This study included 58 eyes of 29 normal subjects and 54 eyes of 28 glaucoma patients. The mean age was 80.7±4.3 years (normal subjects) and 83.1±5.1 years (glaucoma patients). The mean IOP readings were 13.6±3.5 mmHg and 13.2±2.8 mmHg (using the RBT and GAT, respectively) for normal subjects, and 13.6±3.3 mmHg and 13.5±2.9 mmHg for glaucoma patients. The 95% confidence interval of the differences between the two instruments was -3.3 to 4.0 mmHg for normal subjects and -2.9 to 1.6 mmHg for glaucoma patients. The IOP readings by two instruments were significantly correlated with CCT in eyes with glaucoma (for the RBT, β=0.036 and P=0.002, and for the GAT, β=0.021 and P=0.033) but not in normal eyes. CONCLUSION IOP readings measured using the RBT and GAT showed within the allowable range in the late elderly subjects with or without glaucoma. Eyes with glaucoma were correlated closely with CCT using each instrument.