Comparison of three rebound tonometers in normal and glaucomatous dogs

OBJECTIVE: The objectives of the study were to compare intraocular pressure (IOP) readings across a wide range and obtained via three rebound tonometers in ADAMTS10‐mutant Beagle‐derived dogs with different stages of open‐angle glaucoma (OAG) and normal control dogs and to investigate the effect of central corneal thickness (CCT). ANIMALS STUDIED: Measurements were performed on 99 eyes from 50 Beagle‐derived dogs with variable genetics—16 non‐glaucomatous and 34 with ADAMTS10‐OAG. Seventeen OAG eyes were measured twice—with and without the use of IOP‐lowering medications. PROCEDURES: IOP was measured in each eye using three tonometers with their “dog” setting—ICare® Tonovet (TV), ICare® Tonovet Plus® (TVP), and the novel Reichert® Tono‐Vera® Vet (TVA)—in randomized order. CCT was measured with the Accutome® PachPen. Statistical analyses included one‐way ANOVA, Tukey pairwise comparisons, and regression analyses of tonometer readings and pairwise IOP‐CCT Pearson correlations (MiniTab®). RESULTS: A total of 116 IOP measurements were taken with each of the three tonometers. When comparing readings over a range of ~7–77 mmHg, mean IOPs from the TV were significantly lower compared with TVP (−4.6 mmHg, p < .001) and TVA (−3.7 mmHg, p = .001). We found no significant differences between TVA and TVP measurements (p = .695). There was a moderate positive correlation between CCT and IOP for TVA (r = 0.53, p < .001), TVP (r = 0.48, p < .001), and TV (r = 0.47, p < .001). CONCLUSIONS: Our data demonstrate strong agreement between TVP and TVA, suggesting that the TVA may similarly reflect true IOP values in canines. CCT influenced IOP measurements of all three tonometers.