Objective To validate intraocular pressure (IOP) readings obtained in cats with the TonoVet® tonometer.
Animals studied IOP readings obtained with the TonoVet® were compared to IOP readings determined by manometry and by the Tono-Pen XL™ in 1 normal cat and two glaucomatous cats. TonoVet® and Tono-Pen XL™ readings were also compared in a further six normal and nine glaucomatous cats.
Procedures The anterior chambers of both eyes of three anesthetized cats were cannulated and IOP was varied manometrically, first increasing from 5 to 70 mmHg in 5 mmHg increments, then decreasing from 70 to 10 mmHg in 10 mmHg decrements. At each point, two observers obtained three readings each from both eyes, with both the TonoVet® and Tono-Pen XL™. IOP was measured weekly for 8 weeks with both tonometers in six normal and nine glaucomatous unsedated cats. Data were analyzed by linear regression. Comparisons between tonometers and observers were made by paired student t-test.
Results The TonoVet® was significantly more accurate than the Tono-Pen XL™ (P = 0.001), correlating much more strongly with manometric IOP. In the clinical setting, the Tono-Pen XL™ underestimated IOP when compared with the TonoVet®.
Conclusions Both the TonoVet® and Tono-Pen XL™ provide reproducible IOP measurements in cats; however, the TonoVet® provides readings much closer to the true IOP than the Tono-Pen XL™. The TonoVet® is superior in accuracy to the Tono-Pen XL™ for the detection of ocular hypertension and/or glaucoma in cats in a clinical setting.