Determination of Schirmer tear test-1 values in clinically normal alpacas (Vicugña pacos) in North America

To determine the normal reference range for Schirmer tear test-1 (STT-1) values in eyes of healthy alpacas (Vicugña pacos).

Complete ophthalmic examinations were performed on forty healthy alpacas (80 eyes). STT-1 values were obtained in both eyes of all alpacas using a commercial STT strip of a single lot number. Data were analyzed, using a doubly repeated measures ANOVA design, Student's paired t-test, and Pearson correlation test, with P ≤ 0.05 considered significant.

The STT-1 values ± standard deviation (SD) were 20.80 ± 4.01 mm/min OD, 20.00 ± 4.13 mm/min OS, and 20.88 ± 4.04 mm/min OU (range 15.50-30.50 mm/min). No significant differences in STT-1 were found between OD and OS. STT-1 was not significantly affected by breed. Schirmer tear test-1 values were significantly increased by 3.45 mm/min for every 10 year increase in age.

This study provides a reference range of STT-1 in the healthy alpaca which can assist veterinarians in diagnosing potential keratoconjunctivitis sicca, tear film abnormalities, as well as ocular surface diseases in alpacas.