Reference values for Schirmer tear tests I and II in clinically normal pigs

Abstract

To determine reference values for Schirmer tear tests I and II in clinically normal pigs. Twenty clinically normal Landrace pigs (10 males and females) without ocular abnormalities were used in this study. In all pigs, Schirmer tear tests (STT) I and II were performed by using a sterile Schirmer tear test standardized strip (Schirmer-Tränentest(®), Germany) placed in the lower conjunctival fornix for 1 min. For each test (STT I and STT II), no differences were observed between the right and left eyes (P ≥ 0.5). The mean ± SD STT I value was 15.6 ± 3.7 mm/min (range, 10-22 mm/min), while the mean STT II value was 12.4 ± 3.8 mm/minute (range, 5-18 mm/min). The mean STT II value was significantly lower than the STT I level (P < 0.001). Animal gender did not have a significant effect on STT I and II values (P = 0.52). The mean ± SD STT I/II values of 10 juvenile pigs were significantly lower than the mean ± SD STT I/II values of 10 adult pigs (P < 0.001). This study of 20 Landrace pigs provided valuable information on normal STT I/II in this species. Knowledge of normal STT reference values in pigs enables the clinician to evaluate corneal pathology and diagnose tear deficiency syndromes with greater accuracy.