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 (R) Tono-Vera (R) 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 IOPlowering medications were administered.Procedures: In each dog, tonometry was performed with the Tono-Vera (R) 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 (R)).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 TonoVera (R) Vet measurements conducted without the aid of the positioning system still provide reliable results.