Comparison of Intraocular Pressure Measurements in 500 Calves Using Tono-Pen Vet® and Tonovet®

Intraocular pressure (IOP) measurement is one of the important parameters used to evaluate the development of ocular disorders.The aim of this study was to determine and compare the IOP readings in calves obtained with Tono-Pen Vet® and TonoVet® tonometry from a total of 500 calves of different breed, age, sex, degree of dehydration, eye-side and under different diurnal variation factors.Three to five minutes after two drops of 2% lidocaine ophthalmic anesthetic were applied to both eyes, a randomized tonometer protocol and eye order were used to measure the intraocular pressure in both eyes.Calculated mean IOP±SD with the Tono-Pen Vet® was 20.18±2.284mmHg (13-27 mmHg) and 16.34±2.195mmHg (11-23 mmHg) for TonoVet®.Readings from Tono-Pen Vet® were noticeably higher, with a mean difference of 3.84 mmHg (P < 0.001).A moderate connection between the devices was found using linear regression analysis (y = 0.750x + 7.923; r 2 = 0.5792), suggesting that the instruments are connected but not interchangeable.Although IOP did not show significant differences in breed, sex, and eye-side (P > 0.05), whereas it displayed significant differences related to age and diurnal variation (P < 0.05).It was determined that the eye pressure was higher during morning and afternoon measurements compared to evening.Even though there was a statistically significant difference based on hydration state, the small number of dehydrated calves necessitates careful interpretation.In conclusion, Tono-Pen Vet® consistently overestimates IOP in calves when compared to TonoVet®.Age and measurement time should be taken into considerations in clinical practice.