Validation of the iFalcon V100 Rebound Tonometer in Canine Eyes

To validate the accuracy of the iFalcon V100 rebound tonometer in measuring intraocular pressure (IOP) in enucleated normal canine eyes.

Four freshly enucleated normal canine eyes tested within 12 h postmortem.

A 1.5 mL water syringe was inserted into the vitreous chamber, and an implantable pressure sensor was inserted into the anterior chamber. IOP measurements were initiated at 5 mmHg and gradually increased to 50 mmHg by incrementally advancing the syringe plunger. Measurements were taken with the iFalcon V100 from the central cornea using the canine mode, and results were compared to those obtained from the implantable pressure sensor using linear regression analysis and Bland-Altman plots.

The iFalcon V100 readings showed a strong linear correlation with the implantable sensor (r² = 0.96). Bland-Altman analysis revealed a mean bias of +0.34 mmHg, with 95% limits of agreement ranging from -4.29 to +4.98 mmHg; the overestimation was slightly in the lower pressure range. Notably, multiple attempts were required to obtain the measurements at 5-10 mmHg with the iFalcon V100.

The iFalcon V100 tonometer provides accurate central corneal IOP measurements in normal canine eyes within the physiological range of 5-50 mmHg, showing good agreement with direct implantable pressure sensor readings. Although the validated 5-50 mmHg range is wider than normal physiological pressures and encompasses commonly encountered pathological levels, we did not evaluate performance at 70-80 mmHg levels occurring in acute glaucoma, which is a study limitation.