Osmolarity of basal and reflex tears of normal dogs

Objective To compare basal and reflex tear osmolarity in healthy dogs and to evaluate for correlation among tear film osmolarity, tear production, and tear fern pattern. Animals studied The population consisted of 22 healthy adult dogs. Procedures Reflex tear osmolarity was measured in both eyes using the I‐PEN® VET osmometer 30 minutes following the Schirmer tear test (STT‐1) measurement. Subsequently, two minutes following topical anesthetic application, the lacrimal lake and conjunctival fornices were dried, and 3 minutes later, basal tear osmolarity was measured. Tears were extracted from the dye‐free STT‐1 strip by centrifugation, placed on a glass slide, and the ferning pattern was determined by light microscopy. Comparisons between basal and reflex tears were performed with one‐way ANOVA. Correlations between tear osmolarity, STT‐1, and tear ferning were verified by Pearson's correlation coefficient. Results No statistical difference was found between right and left eyes for STT‐1, tear fern pattern, and osmolarity of reflex or basal tears (P