Comparison of measurement performance among Tono-Vera vet, Tono-Pen vet, and Tono-Vet plus using an ex vivo porcine eye model.

Abstract

Background: Accurate measurement of intraocular pressure (IOP) is critical in veterinary ophthalmology, yet performance differences between handheld tonometers remain a clinical challenge. This original article aims to directly evaluate the newly launched Reichert^® Tono-Vera Vet (TVV) compared to two commonly used tonometers, the Icare^® Tono-Vet Plus (TVP) and Reichert^® Tono-Pen Vet (TPV), using an ex vivo porcine eye model across a wide range of IOP levels.

Methods: Ten eyes were used to compare the accuracy and consistency of TVV, TVP, and TPV across physiological (5-25 mmHg) and high (30-70 mmHg) intraocular pressure (IOP) ranges. Bias assessment, Bland-Altman plots, regression analysis, and receiver operating characteristic (ROC) analysis were conducted.

Results: TVV demonstrated superior accuracy in the physiological range, with a mean deviation of 1.16 ± 2.31 mmHg and narrow limits of agreement (min =-3.38 mmHg, max = 5.69 mmHg). At higher pressures, TVV's variability increased (mean deviation = 0.566 ± 5.95 mmHg). TVP consistently overestimated IOP, particularly at high pressures (mean deviation = 5.68 ± 6.46 mmHg), while TPV significantly underestimated IOP (mean deviation =-11.0 ± 8.55 mmHg; p < 0.001). Bland-Altman analysis confirmed TVV's better agreement with true IOP in the physiological range. Regression analysis showed a strong correlation for TVV (R² > 0.90), and ROC analysis highlighted its strong discriminative ability (AUC = 0.913). None of the devices effectively differentiated accurate measurements at high IOPs.

Conclusions: TVV outperformed TVP and TPV in accuracy and consistency, particularly for physiological IOPs. Its reliability supports its use in routine IOP assessments, though all devices showed limitations at elevated pressures.