Tear production in normal juvenile dogs

Objective To establish a baseline range or average for tear production in normal juvenile dogs and evaluate the effects of age, weight, and gender on Schirmer tear test (STT) in juvenile dogs. Materials and methods Healthy puppies of various breeds < 6 months of age. STT1 and STT2 were performed in both eyes of each subject. Statistical analysis was performed using a backwards stepwise regression model with repeated measures. Using continuous variables of STT1 and STT2 as the dependent variables separately, the independent variables were age (days), eye (left or right), gender (male or female), ocular disease processes in eyes or not, and weight (kg). Results Eighty-six eyes from 27 males and 16 females were included in this study. Ages ranged from 25 to 133 (mean +/- SEM: 61.74 +/- 24.15) days and weights ranged from 0.88 to 8.86 (3.27 +/- 2.22) kg. STT1 results ranged from 0 to 26 (15.76 +/- 5.79) mm/min. STT2 results ranged from 0 to 24 (8.79 +/- 5.01) mm/min. Age, weight, and gender significantly affected STT1 results. Weight and gender significantly affected STT2 results. STT1 values increased by 0.15 mm/min for each 1 day increase in age and by 0.84 mm/min for each 1 kg increase in body weight. STT2 values increased by 0.57 mm/min for each 1 kg increase in body weight. Conclusions Age, weight, and gender significantly affect tear production in normal juvenile dogs. STT1 increases to adult values at approximately 9-10 weeks of age.