Efficacy of the positioning system when measuring canine intraocular pressures with the Reichert® Tono-Vera® Vet rebound tonometer.

OBJECTIVE: To compare intraocular pressure (IOP) measurements in dogs taken with the Reichert® Tono-Vera® Vet rebound tonometer with and without the automatic positioning system. ANIMALS STUDIED: Measurements were taken on 49 eyes from 26 Beagle-derived dogs with variable genetics-four non-glaucomatous and 22 ADAMTS10-mutant dogs affected with different stages of open-angle glaucoma. Seventeen of the 26 dogs were measured 2-4 times on different days with variable intervals since IOP-lowering medications were administered. PROCEDURES: In each dog, tonometry was performed with the Tono-Vera® Vet using three different methods in a randomized order: (Method 1) Average of three readings with an automatic positioning system; (Method 2) one reading with an automatic positioning system; and (Method 3) average of three readings obtained without the automatic positioning system. Statistical analyses included one-way ANOVA, Tukey pairwise comparisons, and Bland-Altman plots (MiniTab®). RESULTS: With each of the three tonometry methods, 116 measurements were taken, resulting in 348 total IOP measurements with a range of 12.8-49.9 mmHg. The means and standard deviations for each method were 25.4 ± 6.9 mmHg (Method 1), 26.0 ± 7.2 mmHg (Method 2), and 26.9 ± 7.7 mmHg (Method 3), with no significant differences (p = .27). Mean IOP variances were also not significantly different between tonometry methods (p = .24 to .78). CONCLUSIONS: Because mean IOPs and their standard deviations were not statistically different between the three tonometry methods, we conclude that Tono-Vera® Vet measurements conducted without the aid of the positioning system still provide reliable results.

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.