Tear production levels in dogs with watery eyes and corneal damage

Abstract

Measurement of tear volume by phenol red thread tear test (PRT), Schirmer’s tear test (STT‐1) and Schirmer’s tear test with topical anesthesia (STT‐2), and vital staining with a combination of fluorescein and rose Bengal of the cornea were performed in dogs with normal eyes and those with epiphora. The breeds included the Shih‐Tzu (n = 26), and five other breeds (n = 50). The PRT, STT‐1 and STT‐2 results from the five breeds of normal dogs were 26.9 ± 3.0 mm, 17.4 ± 4.3 mm, and 8.8 ± 3.2 mm, respectively. The PRT, STT‐1, and STT‐2 results for the Shih‐Tzu eyes were (mean ± standard deviation): 28.2 ± 4.3 mm, 19.5 ± 4.1 mm, and 9.2 ± 4.5 mm, respectively. In the five breeds, corneal epitheliopathy, as evidenced by the retention of topical fluorescein and rose Bengal, occurred in 97% of dogs with epiphora and in 55% of the dogs without epiphora. Also in the dogs with corneal epitheliopathy the STT‐2‐value was low (4.0 ± 2.8 mm) compared with those eyes without corneal epitheliopathy (8.8 ± 3.1 mm). In the Shih‐Tzu breed the STT‐2 results were not significantly different between those dogs with corneal epitheliopathy and those with normal corneas. In the non‐Shih‐Tzu breeds the decrease in basic tear secretion, as measured by the STT‐2, is associated with the corneal epitheliopathy.