Validation And Comparison Of Four Handheld Tonometers In Normal Ex Vivo Canine Eyes

Objectives To determine the accuracy and precision of the Icare(R) TONOVET Plus rebound tonometer and the Tono-Pen AVIA Vet (TM) applanation tonometer for intraocular pressure (IOP) measurement in normal ex vivo canine eyes and comparison to earlier models of these tonometers.Animals & procedures The anterior chambers of six normal dog eyes were cannulated ex vivo. IOP was measured with the TONOVET (TV01), TONOVET Plus, Tono-Pen Vet (TM), and Tono-Pen AVIA Vet (TM) at manometric IOPs ranging from 5 to 70 mm Hg. Data were analyzed by linear regression, ANOVA and Bland-Altman plots. A P value <= .05 was considered significant.Results Intraocular pressure values obtained using the TONOVET Plus and TV01 were significantly more accurate than with the Tono-Pen VET and Tono-Pen AVIA Vet, particularly at higher IOPs (30-70 mm Hg). Accuracy was not significantly different between any of the devices in the low to normal physiologic IOP range (5-25 mm Hg). Level of precision was high for all devices, though the TONOVET Plus was more precise than the Tono-Pen Vet in the 5-25 mmHg range and the TV01 was more precise than the Tono-Pen AVIA Vet over the whole IOP range.Conclusions All devices underestimated IOP, particularly at higher pressures. Rebound tonometers were more accurate over the full range of IOP tested and in the high IOP range; however, there were no significant differences in accuracy among devices in the physiologic IOP range. All tonometers can provide clinically useful IOP readings in dogs, but rebound and applanation tonometers should not be used interchangeably.