Intraocular Pressure Reference Values Comparing Two Rebound Tonometers (TonoVet and TonoVet Plus) in Male Camels...

To determine the intraocular pressure (IOP) reference values in healthy male camels using two rebound tonometers: TonoVet (TV) and TonoVet Plus (TV+), and to compare measurements between both devices and in different body positions.

Thirty-four healthy, captive, adult (8-24 years and a median age of 14), male camels belonging to a zoological collection in Fuerteventura, Spain.

All camels underwent general physical examination, slit lamp biomicroscopy, and tonometry, under minimal physical restraint (headstall and chute). Three consecutive readings were acquired with TV and/or TV+ in the right and/or left eyes in standing and/or sitting positions, whenever possible. Comparisons between groups were made when paired data for the test variable was available for the same eye (for tonometer and body position) or for the same animal (for left and right eyes) using paired t-tests.

The mean IOP (± standard error and range) in standing position was 18.51 mmHg (0.52, 10.33-24.33 mmHg) for TV and 19.53 mmHg (0.50, 12.33-26.33 mmHg) for TV+. In sitting position, the IOP was 14.70 mmHg (0.49, 11.33-18.33 mmHg) for TV and 16.28 mmHg (0.47, 13-19.66 mmHg) for TV+. Measurements for both TV and TV+ were significantly higher (p = 0.003 and p = 0.011, respectively) in standing position. Recordings with TV+ were significantly higher than with TV, in any body position (p < 0.001 and p = 0.006, respectively). There were no statistically significant differences between right and left eyes, except for TV+ in standing position, with the IOP in the left eye being significantly higher (20.58 mmHg versus 18.51 mmHg, p = 0.004).

To the authors' knowledge, this is the first report estimating the IOP reference values in male camels comparing two different rebound tonometers. Measurements for both TV and TV+ were significantly higher in the standing position. Recordings with TV+ were significantly higher than with TV (in any body position). Further studies with female individuals and different age groups are warranted.