Research Article Open Access

Measurement of tear osmolarity in the canine eye: a new diagnostic tool for canine keratoconjunctivitis sicca?

Abstract

In this study the osmolarity of the canine tear film as measured by the TearLab micro-osmometer was compared with the Schirmer Tear Test I (STT) in 100 dogs from the patient population at the Queen’s Veterinary School hospital, University of Cambridge and a UK animal rehoming facility. 153 eyes were ophthalmoscopically normal and 47 had varying degrees of keratoconjunctivitis sicca (KCS) as determined by STT values below 15mm/min.

Animals underwent a full ophthalmic examination and then were sampled using the TearLab device to measure tear osmolarity followed by a standard Schirmer tear test I. Tear osmolality in eyes with normal tear production was compared to that in eyes with KCS using the Student’s T test. Correlation between STT and osmolarity data was investigated using the Pearson rank correlation coefficient. Tear osmolality was significantly higher in eyes with KCS (350 ± 27 mOsm) than in normal eyes (339 ± 23 mOsm) this difference significant at p<0.02. As high tear omolarity is considered to be a key factor in the pathogenesis of ocular surface damage in eyes with aqueous tear film deficiency in human patients, measuring tear film osmolarity in dogs with suspected KCS may be an important diagnostic step in these animals.

Williams DL and Buckingham A.

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