Abstract
The purpose of this study was to evaluate and establish the mean values of IOP in healthy adult sheep using an applanation tonometer. Information on age, sex, and breed was obtained for all animals included in this study. Twenty five healthy sheep (Ovis aries), of the same breed (Texel), male or female, with three years of age, received an ophthalmic examination in both eyes, including pupillary reflexes, Schirmer tear test, slit lamp biomicroscopy, and fluorescein staining. For all ophthalmic testing, animals were gently physically restrained, with no pressure in the jugular area and the eyelids were carefully open. IOP was measured by applanation tonometry (Tonopen XL). The same examiner performed the tonometry; measurements were taken three times for each eye, and their average was recorded as the IOP of the animal. Statistical analysis was performed using paired t-test and values of P < 0.05 were considered significant. The mean intraocular pressure in the whole group of 50 eyes was of 16.36 +/- 2.19 mm Hg. The mean (SD) IOP in the right eye was of 15.96 +/- 2.02 mm Hg, while the mean (SD) IOP in the left eye was of 16.76 +/- 2.32 mm Hg. Significant differences in IOP were not found between right and left eyes. The applanation tonometer was adequate for measuring the intraocular pressure in sheep. Reference data will assist in diagnosing testing for ophthalmic disease in sheep, as¹ well as promote further studies in this area.
Highlights
MATERIALS AND METHODSIntraocular pressure (IOP) is determined by the production and drainage of aqueous humor (Slatter, 2005)
The tonometer used in this study, Tonopen XL, has the same characteristics as the MacKay-Marg applanation tonometer, which is considered the golden standard in Veterinary Medicine, it has no longer been manufactured (Rusanen et al, 2010)
There are quite a few studies using applanation tonometry in animals (Priehs et al, 1990; Miller et al, 1990; Miller et al, 1991; Dziezyc et al, 1992; Passaglia et al, 2004; Candia et al, 2010; Gerometta et al, 2010; Ribeiro et al, 2010; Rusanen et al, 2010), but we found no reports on the assessment of the mean IOP in healthy sheep using the applanation tonometer Tonopen XLe
Summary
Intraocular pressure (IOP) is determined by the production and drainage of aqueous humor (Slatter, 2005). Sheep have become popular as production animals and they have been identified as a model for steroid-induced ocular hypertension with 100% of susceptibility (Passaglia et al, 2004); it is important to know the mean intraocular pressure using an easy handling tonometer. Thirty seconds after the application of anesthetic drops, and having their eyelids manually retained open; the applanation tonometry was performed in both eyes (Figure 1). The data for both eyes of each animal were recorded. Means of intraocular pressures obtained from both eyes were compared by statistical data analysis using Tukey’s test, and values of P < 0.05 were considered significant
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