Correlation between Tear Osmolarity and Other Ocular Surface Parameters in Primary Sjögren's Syndrome

PURPOSE To investigate the relationships between tear osmolarity and other ocular surface parameters and to determine the diagnostic value of tear osmolarity in primary Sjögren's syndrome (SS) using tear film break-up time, Schirmer I test, and cornea/conjunctiva staining. METHODS We included 310 eyes of 155 patients diagnosed with dry eye disease (39 primary SS and 116 non-Sjögren dry eye disease) at Seoul St. Mary's Hospital from August 2010 to January 2015. All subjects completed the Ocular Surface Disease Index (OSDI) questionnaire and underwent ocular examinations including tear osmolarity (TearLab Osmolarity System), Schirmer I test, slit lamp examination for tear film break-up time, and corneal and conjunctival fluorescein staining. We used the mean value of both eyes for all parameters. Fluorescein staining was assessed using the Sjögren's International Collaborative Clinical Alliance ocular staining score (OSS). RESULTS In primary SS patients (n = 39), the mean subject age was 52.5 ± 11.9 years, and 94.9% of the subjects were women. Mean tear osmolarity in SS was 311.1 ± 16.4 mOsm/L, with 16 (41.0%) subjects having values ≥316 mOsm/L. In SS, there was a positive correlation between mean tear osmolarity and OSDI score (ρ = 0.405, p = 0.011) and OSS (ρ = 0.592, p < 0.001). There was a negative correlation between mean tear osmolarity and the Schirmer I test (ρ = -0.625, p < 0.001). There was no significant correlation between mean tear osmolarity and tear film break-up time in SS (ρ = 0.110, p = 0.505). CONCLUSIONS Tear osmolarity measurements using the TearLab Osmolarity System can reflect both symptom severity (OSDI) and objective signs (Schirmer test and OSS) in SS.