Reference values for intraocular pressure and Schirmer tear test in healthy wild European mouflons (Ovis orientalis musimon)

Introduction - In the context of the eye investigation, standard diagnostic ophthalmic test, as intraocular pressure (IOP) and Shirmer Tear Test (STT) values, could be useful to improve the clinical ophthalmic approach to the domestic animals. Large interspecies and intraspecies variations in reference STT and IOP values have been documented. Aim - The current study was undertaken to establish reference values for STT and IOP in European wild mouflons living on the Island of Sardinia. Materials and methods - Thirty-six healthy wild mouflons with no evidence of ocular disease were enrolled in this study. All animals were >= 2 years of age; mean (+/- standard deviation) age of the animals (26 male and 10 female) was 34.2 +/- 7.5 months. Tear production was measured using the Schirmer tear test type I; intraocular pressure was recorded using an applanation tonometer. The unsedated animals were placed in sternal decubitus. Statistical analysis of data was performed using multivariate analysis of variance (MANOVA) in order to determine significant effects of different gender (male; female), age (24-36 months; 37-48 months) and eye (right; left) on the parameters studied. Results and discussion - Comparison between mean STT and IOP values in males (n = 26) and females (n = 10) showed a significant difference (P=0.001 and P<0.001 respectively). This can be related to the type of sample disproportionately in favor of males, which may have distorted the statistical comparison. However, this finding is in accordance with some studies that report that gender may affect IOP only in some species, including humans and lions. No significant effects of animal age (2436 months; 37-48 months) and eye (left versus right) on STT and IOP values were found in this study. Mean STT values were 15.50 +/- 1.71 mm/min (n= 52) when measurements from both eyes were averaged (range of 11-18 mm/min). Mean IOP values for all mouflon eyes (n= 52) were 18.05 +/- 4.85 mmHg, with a range of 11-25.66 mmHg. Conclusions - This study reports STT and IOP findings in European mouflons and provide means and ranges for these ocular diagnostic parameters as useful data for evaluation of ocular diseases in this animal specie.