Evaluation of agreement of IOP measurements by Tono-Vera tonometer to Goldmann applanation tonometry.

Purpose: To evaluate the accuracy of the new Tono-Vera rebound tonometer (Reichert Inc, Buffalo, NY) compared to Goldmann Applanation Tonometry. Methods: This prospective, observational, cross-sectional study was designed in accordance with ANSI Z80.10-2014 and ISO 8612-2009 guidelines for tonometer comparison. Intraocular Pressure (IOP) was measured by Goldmann Applanation and Tono-Vera on 160 eyes of 160 subjects. Corneal Astigmatism and Central Corneal Thickness were also measured. A single investigator (CN) conducted all measurements. The average of two measurements from each tonometer was used in the analysis. Bland-Altman plots, total least squares regression analysis, and simple linear regression were used to evaluate agreement between the tonometers. Results: Average IOP values from Goldmann Applanation and Tono-Vera were not significantly different (19.17 and 19.03 respectively, p=0.40, paired t-test). The total least squares regression analysis indicated strong agreement between the two tonometers (slope +0.97, offset +0.49 mmHg, standard deviation 2.11 mmHg). There were 2 IOP measurement pairs that exceeded the ± 5 mmHg limits of agreement required in ANSI Z80.10-2014 and ISO 8612-2009, which is within the range of acceptability specified in the standards. Conclusion: We evaluated IOP measurements by Tono-Vera Rebound Tonometer vs Goldmann Applanation Tonometry for eyes with a wide range of IOP values and found no statistically significant differences in the results. Tono-Vera meets the requirements of ANSI Z80.10-2014 and ISO 8612-2009, demonstrating accuracy comparable to Goldmann tonometry.

Validation of a novel rebound tonometer (Tono-Vera® Vet) in normal ex vivo rabbit eyes.

OBJECTIVE: The purpose of this study was to validate the use of the Reichert Tono-Vera® Vet tonometer rabbit setting in normal ex vivo rabbit eyes and to compare the rabbit setting to the dog, cat, and horse settings of this tonometer. PROCEDURE: Six freshly enucleated normal rabbit eyes were cannulated and connected to a fluid reservoir and physiologic monitor. Triplicate measurements were obtained with the four available settings: dog, cat, horse, and rabbit at various intraocular pressures (IOP) ranging from 5 to 80 mmHg. Bland-Altman analysis was utilized to determine bias and 95% limits of agreement for each setting. RESULTS: Linear regression equations for the dog, horse, cat, and rabbit settings were y = 0.8101x + 2.5058, y = 0.7594x - 3.4673, y = 0.6635x + 0.3021, and y = 0.8935x + 1.3295, respectively. All settings demonstrated strong positive linear trends (dog r2 = 0.9644, horse r2 = 0.9456, cat r2 = 0.9309, and rabbit r2 = 0.9558). Bland-Altman plots revealed that the average bias and 95% limits of agreement (mmHg) were -4.73, -12.65, -12.86 and -2.73 and (-15.31, 5.86), (-29.03, 3.74), (-25.67, -0.05), and (-12.21, 6.76) for the dog, horse, cat, and rabbit settings, respectively. CONCLUSION: The Tono-Vera® Vet rabbit setting provided the most accurate and precise measurements compared with the other settings, but slightly underestimated actual IOP, especially as IOP was increased. This tonometer, using the rabbit setting, is likely to be appropriate for the estimation of IOP in rabbits with the appropriate correction formula applied.

Calibration of a novel rebound tonometer (Tono-Vera® vet) in the porcine eye.

OBJECTIVE: Porcine models of ocular disease are becoming increasingly utilized. A recently commercialized ocular tonometer, the Reichert Tono-Vera® Vet, has not been evaluated for use in pigs. The purpose of this study was to calibrate this device for use in porcine eyes and to determine which settings are most appropriate for use in pigs. PROCEDURE: The anterior chambers of five freshly enucleated normal porcine eyes were cannulated then connected to a reservoir of balanced salt solution and a physiologic monitor. Triplicate measurements were obtained with the four available settings: dog, cat, horse, and rabbit at intraocular pressures ranging from 5- to 80 mmHg. Bland-Altman analysis was utilized to determine bias and 95% limits of agreement for each setting. RESULTS: There was a strong positive linear regression trend for all settings (dog r2  = 0.986, horse r2  = 0.947, cat r2  = 0.977, and rabbit r2  = 0.982). The linear regression equations for the dog, horse, cat, and rabbit setting were y = 1.0168x - 2.6128, y = 0.8743x - 3.4959, y = 0.9394x - 7.3188, and y = 1.1082x - 3.4077. The average bias and 95% limits of agreement for dog, horse, cat, and rabbit settings were - 2.00, -8.32, -9.58, and 0.57 mmHg, and (-7.52, 3.53), (-19.00, 2.37), (-16.66, -2.50), and (-7.79, 8.93), in mmHg. CONCLUSION: The Tono-Vera® Vet dog setting was most accurate and precise setting compared to true intraocular pressures. This setting is likely to be appropriate for in vivo use in pigs, with the appropriate correction formula applied.