Assessing Agreement of Intraocular Pressure from Four Mechanistically Different Tonometers in the Eye Dynamics and Engineering Network Clinical Trial.

Purpose: To compare the measurements of intraocular pressure (IOP) by four mechanistically different tonometers in healthy participants from the Eye Dynamics and Engineering Network Aqueous Humor Dynamics clinical trial using the mean difference estimation, equivalence statistics, and adjusting for proparacaine's effects on IOP.

Design: Multicenter open-label clinical trial in healthy adults (NCT01677507).

Participants: Enrolled were 122 participants (55.2 ± 8.8 years; 92 women and 30 men), 121 of which had measurements with and without proparacaine.

Methods: Participants from 3 sites had their IOPs measured with iCare rebound tonometer (RT), ocular response analyzer corneal-compensated (CC), pneumatonometer (PN), and Goldmann applanation tonometer (GAT). Intraocular pressure readings with RT and CC were collected with and without proparacaine.

Main outcome measures: Effect sizes and agreement in IOP measurements from the four tonometers was analyzed with Data analysis using Bootstrap-Coupled ESTimation, Bland-Altman Limits of Agreement (LoAs), Lin's concordance correlation coefficient (CCC), and robust equivalence two 1-sided t-tests in tandem with null hypothesis significance testing. Data analysis using bootstrap-Coupled ESTimation was used to analyze differences in IOP readings from RT and CC before and after administering proparacaine.

Results: Data analysis using Bootstrap-Coupled ESTimation, LoA, and CCC showed greatest effect size and poorest agreement between PN and the other tonometers. The lowest mean difference was seen when comparing GAT and CC. However, LoA and CCC found the strongest agreement between RT and GAT. Two 1-sided tests revealed tonometers can be considered equivalent to one another at ± 2 mmHg, except for PN. After applying proparacaine, IOP decreased significantly (P < 0.0001) by RT (1.2 ± 1.9 mmHg right eye [OD]; 1.1 ± 1.7 mmHg left eye [OS]), and CC (1.4 ± 1.8 mmHg OD; 1.3 ± 2.3 mmHg OS).

Conclusions: When adjusted for proparacaine's effect on IOP, 3 tonometers were equivalent between each other when determined by equivalence statistical testing with equivalence bounds ± 2 mmHg. The PN reads >2 mmHg higher than RT, CC, or GAT. Therefore, when comparing IOP data from different tonometers, one should consider that not all tonometer measurements are interchangeable and the proparacaine effect should be considered.

Financial disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.