Assessment of tear film osmolarity using the IPen® Vet osmometer in Pug and Shih-Tzu dogs with and without keratoconjunctivitis sicca.

Abstract

To establish tear film osmolarity (TFO) values in Pugs and Shih-Tzus, with and without keratoconjunctivitis sicca (KCS). A total of 82 adult dogs were evaluated. The inclusion criteria for the healthy group was a Schirmer tear test (STT-1) ≥15mm/min with no clinical signs of KCS, whereas those with KCS had clinical signs and a STT-1 ≤10mm/min. All animals underwent complete ophthalmological evaluation prior to STT-1 and TFO. Student's t tests were used to compare STT-1 and TFO in KCS and healthy eyes as well as possible differences in TFO between breeds. In addition, a linear regression to model the relationship between the two variables (STT-1 and TFO) was performed. A P-value≤0.05 was considered statistically significant. STT-1 results were significantly lower (p=0.0001) in the KCS group (4.46±1.74) compared with the control group (18.80±2.02). Mean TFO results were significantly higher in the KCS group (353.02±16.58mOsm/L) (p<0.0001) compared with the control group (315.27±6.15mOsm/L). The formula Y=365.059-2.625 * X significantly predicts (p<0.001) the value of the variable Y (TFO mOsm/L) as a function of the variable X (STT-1mm/min), with a coefficient of determination of 0.71. The results revealed differences in TFO and STT-1 between KCS and healthy dogs. Additionally, STT-1 and TFO values were correlated with the aim to use STT-1values to predict TFO values in brachycephalic breeds.