Evaluation of Tear Formation in the Dog, Using a Modification of the Schirmer Tear Test

Abstract

SUMMARY The Schirmer tear test for the measurement of tear formation in the dog was done according to 2 procedures: Schirmer I (the conventional procedure) and Schirmer II (with topical anesthesia and drying of the ventral conjunctival fornix). Results from 97 normal dogs averaged 21.0 mm wetting/minute (standard deviation ( sd ) ± 4.2 mm) for the Schirmer I test and 11.6 mm wetting/minute ( sd ± 6.1 mm) for the Schirmer II test. When atropine was injected subcutaneously in 50 dogs (0.02 mg/kg), wetting/minute averaged 9.36 mm (Schirmer I) and 4.32 mm (Schirmer II). Two dogs in each of 3 groups had either the lacrimal gland, gland of the membrana nictitans, or both excised. Changes in tear formation were evaluated by Schirmer I and II tear tests, as well as after parenteral administration of atropine. The lacrimal gland, the gland of the membrana nicitans, and the accessory lacrimal glands and mucous cells were found to contribute 61.7, 35.2, and 3.1%, respectively, to tear formation.