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

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.