Tonometry in three herbivorous wildlife species

Tonometry was performed to estimate intraocular pressure (IOP) in 12 Nubian ibexes (Capra ibex nubiana), 10 Grant zebras (Equus burchelli) and five Arabian oryxes (Oryx leucoryx), using both applanation (Tono-Pen) and/or indentation (Schiotz) tonometers. Animals were anesthetized with a mixture of etorphine hydrochloride and acepromazine maleate. Mean (± SD) IOP in the ibex was 17.95 ± 4.78 mmHg (24 eyes, indentation tonometry). In the zebra, indentation tonometry (20 eyes) yielded a mean IOP of 25.30 ± 3.06 mmHg, and applanation tonometry (six eyes) yielded a mean IOP of 29.47 ± 3.43 mmHg. In the oryx, indentation tonometry (five eyes) yielded a mean IOP of 22.68 ± 8.15 mmHg, and applanation tonometry (10 eyes) yielded a mean IOP of 11.76 ± 3.43 mmHg. There were no significant effects of gender, age, weight, side or reading number on the IOP measured in any of the three species. No significant differences were found between the IOP of the three species, nor between the readings of the two instruments, although some of the P-values were close to the significance level.