Accuracy of Intraocular Pressure Measurement With the Icare Tonometer in Children.

ABSTRACT

PURPOSE: The aim of this study was to evaluate the difference between intraocular pressure (IOP) measurements in children with the Icare tonomer (IT) and applanation (AT), pneumatic (PT), or digital tonometers (TT). DESIGN: A randomized prospective trial of children younger than age 16 attending the pediatric ophthalmology department of Manchester Royal Eye Hospital was conducted. METHODS: Children had IOP measured twice, once with an IT and again with a TT, PT, or AT during the same clinic appointment. RESULTS: Forty-four children (88 eyes) were included, with a mean [range (R)] age of 57 (2-144) months. Twelve eyes had anterior segment pathology (ASP), defined as aniridia, congenital glaucoma, or Peters anomaly. Regardless of the presence or absence of ASP, total mean difference (MD), R, positive bias (PB), and limits of agreement (LOA) between IT and other instruments were as follows PT MD = 3.2, R = 0 to 8, PB = 2.9, LOA = -1.0 to 6.9; TT MD = 2.6, R = 0 to 6, PB = 0.9, LOA = -1.8 to 3.5; and AT MD = 1.4, R = -3 to 5, PB = 0.6, LOA = -4.2 to 7.3. In eyes with ASP, IT comparisons with PT were as follows MD = 3.9, R = 0 to 8, PB = 3.9, LOA = -0.9 to 8.8. CONCLUSIONS: In children with ASP, IOP measured with IT is higher than expected when compared with other tonometers, in some cases by up to 8 mm Hg. We found an overestimation of IOP in children using the IT with a positive bias of 4 mm Hg. We propose that the IT overestimates IOP measurements in children compared with standard tonometers. Further work should be carried out on a much larger cohort to establish a suitable correction factor for such children.