Estimation of lacrimal level and testing methods on normal beagles

Five methods of testing tears including the Schirmer tear test (STT-1), phenol red thread tear test (PRT) and modified Schirmer tear test (STT-2) were conducted on 44 eyes of 22 normal Beagles, and the tear film break up time (BUT) and lacrimal pH were tested in 32 eyes of 16 normal Beagles. The coefficient of variation of PRT demonstrated a low value (C.V. 12%) [corrected] compared to the value of STT-1 (C.V. 14%) [corrected]. The lacrimal pH showed a more constant value (C.V. 3%). Measurements of STT-2 (C.V. 48%) and BUT (C.V. 34%) varied significantly. The results show the clinical usefulness of the PRT. Mean values (mean +/- SD) of tests were: PRT, 29.3 +/- 3.45 mm/15 s; STT-1, 18.89 +/- 2.62 mm/60 s; STT-2, 9.52 +/- 4.55 mm/60 s; pH, 7.29 +/- 0.22 and BUT, 21.53 +/- 7.42 s.