The utility of a normal tear osmolarity test in patients presenting with dry eye disease like symptoms: A prospective analysis

Objective: To explore the diagnostic utility of normal tear osmolarity in patients with symptoms suggestive of dry eye disease (DED). Methods: Prospective observational cohort study of 100 patients that underwent tear osmolarity testing (TearLab ^™ ) if they endorsed one or more symptoms of potential DED. Patients were included for the study if they had a normal tear osmolarity test (value <308 mOsm/L in each eye, and an inter-eye difference <8 mOsm/L). The main outcome measure was the presence of any alternate diagnosis to explain the patient's symptoms. Results were recorded and descriptive and univariate statistics were employed. Results: Mean tear osmolarity was 293.40 mOsms/L (±6.82), with a mean absolute difference of 2.85 mOsms/L (±1.98) between the eyes. A possible alternate diagnosis was established in 89% of patients with normal tear osmolarity testing. The most frequent diagnoses included anterior blepharitis (26%) and allergic conjunctivitis (21%). Conclusions: Common symptoms of DED overlap significantly with a wide variety of other ocular surface diseases, and a normal tear osmolarity test should increase clinical suspicion for alternate causes of those symptoms. Anterior blepharitis and allergic conjunctivitis were the most common diagnoses made in symptomatic patients with normal tear osmolarity who may have otherwise been misdiagnosed and treated for DED.