Comparison of intraocular pressure measurements using rebound (TonoVet ® ) and applanation (TonoPen-XL ® ) tonometry in clinically normal alpacas (Vicugña pacos).

Purpose: To evaluate intraocular pressure (IOP) estimates in eyes of healthy alpacas (Vicugña pacos) using rebound (TonoVet ^® ) in comparison with applanation (TonoPen-XL ^® ) tonometry.
Methods: Complete ophthalmic examinations were performed on forty healthy alpacas (80 eyes). IOP measurements using both TonoVet ^® and TonoPen-XL ^® tonometers were obtained OU. Data were analyzed, using a doubly repeated-measures anova design and Student's paired t-test, with P ≤ 0.05 considered significant.
Results: The mean IOP values ±SD via rebound tonometry were 14.20 mm ± 2.58 mm OD, 14.22 mm ± 2.90 mm OS, and 14.21 ± 2.73 mmHg OU (range 8.67-20.67 mmHg). The IOP values ±SD via applanation tonometry were 12.49 ± 2.81 mmHg OD, 12.53 ± 2.79 mmHg OS, and 12.51 ± 2.78 mmHg OU (range 6.00-19.33 mmHg). There was a significant difference (P = 0.002) in the IOP obtained between the tonometers, with the rebound tonometer having a 1.7 mmHg (0.69-2.71 mmHg, 95% confidence interval (CI)) higher IOP compared to the applanation tonometer. No significant differences in IOP were found between OD and OS. Age, gender, and breed did not significantly affect IOP values.
Conclusions: IOP readings from the rebound tonometer were statistically higher than those from the applanation tonometer; however, this is not considered clinically significant. The accuracy of rebound tonometry in diseased alpaca eyes remains to be determined.
(© 2016 American College of Veterinary Ophthalmologists.)