Comparison of rebound tonometer and goldmann handheld applanation tonometer in congenital glaucoma

PURPOSE: To compare intraocular pressure (IOP) measurements obtained using the rebound tonometer (RBT) and the handheld Goldmann applanation tonometer (Perkins) in children with congenital glaucoma. METHODS: Using both tonometers, the IOP was prospectively determined in 68 eyes of 68 patients with congenital glaucoma aged 3 to 13 years. Corneal curvature, central corneal thickness (CCT), and axial length were also measured in each patient. The ease of the use of each tonometer was scored using a visual analog scale. RESULTS: IOP readings obtained using the RBT and Perkins tonometer showed good correlation (r=0.869, P<0.001) although RBT readings were consistently higher (mean difference: 3.1 ±4.0'mm Hg). According to the Bland-Altman plot, the 95% limits of agreement between the 2 methods were -4.8 to 10.9'mm Hg (slope=0.589, P<0.001). When estimating CCT, the 2 tonometers behaved similarly and correlation was observed between IOP measurements and CCT, with higher IOPs obtained as the CCT increased. In contrast, no correlation was detected between corneal curvature or axial length and the IOPs recorded using either tonometer. Ease of use scores awarded by the examiner was higher for the RBT. CONCLUSIONS: The RBT overestimates the IOP compared with the Perkins tonometer in patients with congenital glaucoma. Differences in readings between the 2 tonometers become larger as the CCT increases.