Comparison of Disposable Goldmann Applanation Tonometer, ICare ic100, and Tonopen XL to Standards of Care Goldmann Nondisposable Applanation Tonometer for Measuring Intraocular Pressure


Purpose: To compare intraocular pressure (IOP) measurements by Goldmann applanation tonometer (GAT), disposable Goldmann applanation prism, ICare, and Tonopen.

Materials and methods: A total of 74 patients with varying glaucoma status were examined in our outpatient clinic and IOP was measured with 3 tonometers. The disposable Tonojet prism (dGAT), Tonopen XL, and ICare ic100 were compared with the GAT.

Results: There were good intraclass correlation coefficients between IOP measurements by GAT and dGAT (0.95), Tonopen (0.83), and ICare (0.77), all P<0.001. The IOP mean differences between dGAT and GAT were mean 0.80 mm Hg; 95% limits of agreement: -3.35 to 4.96 mm Hg. For Tonopen and GAT: mean, -1.67 mm Hg; limits of agreement, -8.55 to 5.21 mm Hg. For ICare and GAT: mean, 0.44 mm Hg; limits of agreement, -8.18 to 9.06 mm Hg.

Conclusions: The most reliable modality, with good correlation with the Goldmann tonometer values, was the GAT with dGAT, followed in descending order by the Tonopen XL and ICare. There was good interdevice agreement and consistency between all devices. On subgroup analysis, all 3 modalities were found to be less reliable at extreme IOP values (<10 and >24 mm Hg). These disposable modalities should be avoided in extreme IOP ranges outside the normal range.