The Icare-Pro Rebound Tonometer Versus the Hand-held Applanation Tonometer in Congenital Glaucoma

Abstract

To compare intraocular pressure (IOP) measurements obtained using the new rebound tonometer Icare-Pro and the hand-held version of Goldmann Applanation Tonometer (Perkins tonometer) in children with primary congenital glaucoma (PCG) under general anesthesia. Using both tonometers, 3 IOP measurements were prospectively determined in 1 single session. Icare-Pro was always used first, and then Perkins. All measurements were recruited in 50 eyes of 50 patients with PCG under general anesthesia. Central corneal thickness, anterior chamber depth, and axial length were also measured in each patient. Data were compared by determining interclass correlation coefficient for each tonometer and representing the differences detected as Bland-Altman plots. Good linear correlation was observed between IOP readings obtained using the Perkins and Icare-Pro (r=0.75, P<0.001), although the Icare-Pro readings were slightly higher (mean IOP difference 0.42 ± 3.69 mm Hg, P=0.41). A Bland-Altman plot revealed the 95% limits of agreement between the 2 methods: 7.7 to -6.8 mm Hg (slope=0.109, P=0.32). Intraclass correlation coefficient was 0.74 (95% confidence interval, 0.59-0.84) showing good agreement. For both tonometers, no correlation was detected between IOP measurements and central corneal thickness and axial length, but positive relation was found with anterior chamber depth. IOP measurements determined using the new Icare-Pro rebound tonometer showed good correlation with those obtained using the hand-held Perkins applanation tonometer in children with PCG under general anesthesia.