Reference values of Schirmer tear test in sheep and the effect of season on the test results

Abstract

The aim of this study was to determine the reference range of Schirmer tear test (STT) values in sheep using Greek indigenous and mixed breeds and to investigate the potential effect of breed and season on these values. Ninety (30 Chios, 30 Florina and 30 Lacaune mixed breed) ewes aged 2 years or more were used for the study. The aqueous portion of the tear film was measured using Schirmer tear test (STT) commercial strips bilaterally by the same investigator with the animal in standing position. The average STT value recorded was 18.45 ± 3.93 mm/min and the range 10.8–26.2 mm/min. STT was significantly affected by the season and the recorded values were significantly higher in summer compared to winter. The breed had no significant effect on tear secretion. The results of the present study provide a reference range of STT values in sheep and indicate that tear secretion is significantly affected by the season.