The development of the normal Schirmer tear test results during the dog's first year of life

Objective: To evaluate the relationship between lacrimation and age in a homogeneous group of healthy beagle dogs during the first year of life.

Materials and methods: Schirmer tear test I (STT I) was performed at an interval of 12-15 days in both eyes of 16 clinically healthy beagle dogs (eight males and eight females) from 94 to 361 days of age. Three different quadratic polynomial regression equations were estimated for the variation in lacrimation: (1) for the entire period (19 observations), (2) for observations 1-4 (days 94-136), and (3) for observations 5-19 (days 150-361).

Results: By fitting quadratic regression equations to different phases of tear production during the dog's first year of life, it was possible to see that with each day of life, lacrimation increased 0.08 times (8%). From days 94 to 136, however, lacrimal production fell 1.1 times with each day of life. From day 150 to 361, production increased by 0.02 (2%) each day of life. In addition, there was a positive significant and moderate linear correlation between body weight and STT I values (p = .01).

Conclusion: In dogs, during the first year of life, STT I data distribution is parabolic in shape. Age significantly affected tear production. STT I decreased at approximately 108-121 days of age and increased thereafter. Body weight was a significant factor for STT I in young dogs. The establishment of this normal pattern of lacrimation is important for both clinical practitioners and laboratory studies.