Discussion
conjunctival, itching, dry eye disease, fatigue, grittiness, hyperosmolarity, pruritis, dryness
DRY EYE, PATHOGENESIS, EXCESSIVE TEARING, DISEASES, INFLAMMATORY DISEASE
There is no pathognomonic test universally recognized for definitive diagnosis of dry eye. DED is typically diagnosed by symptoms (sensation of dryness or foreign body sensation, excessive tearing, grittiness, eye fatigue, pruritis [itching], and fluctuating vision), and signs (fluorescein and lissamine green vital dye staining, tear film break-up time, and Schirmer testing). Abnormalities of tear osmolarity, i.e. hyperosmolarity has been reported to be key to the mechanism and pathogenesis of DED,The mean tear osmolarity was 303 at baseline and six and 12 months for the whole cohort. For analysis of treatment groups (omega-3 or placebo), the tear osmolarity was significantly different at baseline, but the same in both groups at six and 12 months. Tear osmolarity was increased with aging and increased in subjects diagnosed with Sjögren's syndrome. Tear osmolarity did not correlate with sex, race or systemic health status.Although previous studies suggested tear osmolarity measurement was associated with presence or severity of dry eye disease and may offer a tool for the diagnosis or management of DED,In this study, we found that patients with abnormal osmolarity had more severe dry eye signs, and magnitude of tear osmolarity was significantly correlated with dry eye signs as measured by corneal staining, conjunctival staining, TBUT and Schirmer's test. However, their correlation coefficients were all small ranging from −0.06 (for TBUT) to 0.20 (for conjunctival staining). Furthermore, changes in tear osmolarity over time did not correlate with changes in signs. Similar results were seen with keratography measurement of break up time and bulbar redness, but not with tear meniscus height. Changes in tear osmolarity were not significantly correlated with changes in keratography measurements. The lack of consistent correlations suggests only a weak correlation and one cannot deduce that hyperosmolarity is causative of ocular surface changes.The strengths of the present study included the large data set, a multicenter trial, masked subject evaluation, and same subjects were examined over an extended period of one year. The weaknesses of this study are that we only studied moderate to severe DED in subjects that presented with both signs and symptoms, the study did not include normal subjects or those with mild DED. Although it is difficult to speculate, the results of this study might have changed if normal subjects or those with mild DED were included in this study. As such, it should be emphasized that there is a need for such studies. Tear osmolarity may not be an all or none measurement (one sample of the tear film is analyzed per eye) but may vary with locationIn the DREAM study, tear osmolarity correlated weakly with ocular surface diseases, as defined by the signs measured in DED, and was associated with a known inflammatory disease, Sjögren's syndrome.