The effect of individual biological rhythms on dry eye.

This study aims to assess whether an individual's chronotype (i.e. morningness versus eveningness) has an impact on tear film. Eighty-six dry eye patients not having any underlying systemic or metabolic diseases and either a morning or evening chronotype were included in the study. Tear film break-up time (BUT) and Schirmer tests are common objective tests that are used to diagnose the eye dryness. Using multivariate analysis of covariance (MANCOVA), we investigated the interaction effect of chronotype x sex on insomnia, Schirmer (mm) and BUT (sec) measurements after adjusting for age. We found that the participants who were more prone to evening chronotype characteristics reported to have more severe dry eye signs which monitor with the aid of the Schirmer and tear film break-up time test. In addition, those with higher scores in insomnia severity index had lower Schirmer test and tear film break-up time scores. These findings suggest that chronobiological factors may play a crucial role in the dry eye symptom severity. [ABSTRACT FROM AUTHOR]