Agreement of Intraocular Pressure Measurement of Icare ic200 with Goldmann Applanation Tonometer in Adult Eyes with Normal Cornea.

Purpose: To study the agreement between the Icare ic200 (ICare Finland Oy, Helsinki, Finland) and the Goldmann Applanation Tonometer (GAT) in the measurement of intraocular pressure (IOP) in adult eyes.

Design: Noninterventional, cross-sectional study.

Participants: A total of 156 eyes of 156 adult participants with clear corneas were included.

Methods: The IOP measurements were obtained with the Icare ic200 by 1 observer followed by GAT readings by a second masked observer. The central corneal thickness (CCT) and biometry of all subjects were recorded.

Main Outcome Measures: The agreement between Icare ic200 and GAT was measured using the Bland-Altman plot.

Results: The mean age ± standard deviation of subjects was 55.3 ± 13.7 years. The GAT IOP ranged from 6 to 50 mmHg with a mean IOP of 19.5 ± 8.8 mmHg. The Icare ic200 IOP ranged from 7.4 to 50 mmHg with a mean IOP of 20.8 ± 9.3 mmHg. The mean difference between the IOP measurement of GAT and Icare ic200 was -1.27 mmHg with the 95% limits of agreement (LoA) ranging from -3.4 to 0.9 mmHg for all ranges of IOP. The mean difference (95% LoA) between the IOP measurement of GAT and Icare ic200 was -1 mmHg (-3 to 1 mmHg) and -1.8 mmHg (-4 to 0.2 mmHg) for a GAT IOP ≤21 mmHg and >21 mmHg, respectively. The CCT, axial length, age, and gender did not significantly affect the difference in measurement of IOP between the 2 tonometers. However, for every 1-mmHg increase in GAT IOP, the difference between the 2 tonometers increased by 0.04 mmHg (P < 0.001).

Conclusions: In our study, the Icare ic200 overestimated the IOP. The overestimation increased as the baseline IOP increased. The agreement between the IOP measurement by GAT and Icare ic200 was <2 mmHg at all ranges of IOP. The narrow LoA between the tonometers for an IOP <21 mmHg makes it a useful alternative to GAT in this pressure range.