Agreement of iCare IC200 tonometry with Perkins applanation tonometry in healthy children

Abstract

Purpose: To assess interdevice agreement between the iCare IC200 rebound tonometer and Perkins applanation tonometry (gold standard) in a healthy pediatric population.

Methods: A total of 42 eyes of 42 healthy children were assessed using both tonometers. Data was collected on subject's age, sex, best-corrected visual acuity, and central corneal thickness (CCT). Intraclass correlation coefficient (ICC) and Bland-Altman analyses were used to determine agreement between IC200 and Perkins applanation tonometers. Linear regression analyzed the effects of intraocular pressure (IOP) on device difference.

Results: The mean age and standard deviation of healthy pediatric subjects was 10.0 ± 3.3 years. The mean difference between IC200 and Perkins tonometers (IC200-Perkins) was 0.72 mm Hg, with a mean of 17.1 ± 3.0 mm Hg and 16.4 ± 2.5 mm Hg, respectively. The absolute agreement, or ICC, between tonometers was 0.63 (95% CI, 0.56-0.70). Bland-Altman analysis showed 95% limits of agreement ranging from -5.2 to +6.6 mm Hg. CCT was not correlated with IOP for either the IC200 (P = 0.35) or the Perkins tonometer (P = 0.052).

Conclusions: Compared to applanation tonometry, IC200 overestimated IOP in healthy children, with a greater frequency of readings > +2 mm Hg than < -2 mm Hg compared to Perkins. There was moderate agreement between tonometers. CCT was not found to influence IOP measurement for either tonometer.