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

Abstract

To compare intraocular pressure (IOP) measurements in dogs taken with the Reichert® Tono-Vera® Vet rebound tonometer with and without the automatic positioning system. 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. 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®). 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). 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.