Randomized comparison of in vivo performance of TearLab® and I-PEN® osmometry in normal dogs.

Abstract

OBJECTIVE: To compare tear film (TF) osmolarity measured using TearLab&#xae; and I-PEN&#xae; osmometers in the same dogs without any ocular surface disease. ANIMAL STUDIED: Fifty-two dogs (98 eyes) of different breeds were evaluated. PROCEDURES: Tear film (TF) osmolarity was evaluated at 2-min intervals. The test was randomly determined, and single measurements were performed using each osmometer. Subsequently, complete ophthalmologic examinations were performed based on Schirmer tear test-1 (STT-1) analysis, tear film breakup time (TFBUT), and slit-lamp biomicroscopy. For each osmometer, the mean&#x2009;&#xb1;&#x2009;standard deviation of the TF osmolarity was calculated, and a paired Student's t-test was used to compare the values obtained. Pearson correlation analysis was performed to assess the association between osmolarity and other values such as STT-1, TFBUT, and age. RESULTS: Tear film osmolarity determined using TearLab&#xae; (340.42&#x2009;&#xb1;&#x2009;15.87&#x2009;mOsm/L) and I-PEN&#xae; (321.58&#x2009;&#xb1;&#x2009;17.39&#x2009;mOsm/L) were significantly different (p&#x2009;<&#x2009;.001). However, statistical significance could not be confirmed between osmolarity and other values, such as STT-1, TFBUT, and age. CONCLUSIONS: In dogs, the TF osmolarity values obtained using TearLab&#xae; tend to be higher than those obtained using I-PEN&#xae;, contrary to that observed in humans. These findings can serve as a reference for establishing normal values for each osmometer for clinical use in measuring TF osmolarity in dogs.