Validation of the TonoVet® rebound tonometer in normal and glaucomatous cats

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.