Correlation between tear film osmolarity, dry eye disease, and rheumatoid arthritis

The aim of this study was to evaluate the reliability of tear film osmolarity as a diagnostic tool for detecting dry eye disease (DED) in patients with rheumatoid arthritis (RA). The second aim was to determine whether there is a relationship between tear film osmolarity, a commonly used RA score, and diagnostic blood tests for RA.

A group of 74 patients with RA but without any previously established diagnosis of DED at University Hospital Wurzburg was examined. A Modified Dry Eye Severity Score was calculated based on tear film osmolarity, Schirmer test, tear film break-up time, ocular surface disease index questionnaire, corneal fluorescein staining, conjunctival lissamine green staining, and meibomian gland grading score. RA assessment included disease activity score (DAS) 28-erythrocyte sedimentation rate (ESR) scoring and serum levels of C-reactive protein (CRP) and rheumatoid factor (RF).

Tear film osmolarity showed a high coefficient of determination and correlation when regressed to Modified Dry Eye Severity Score (R = 0.727, P < 0.001). Using a cutoff point of 316 mOsmol/L, there was significant correlation between DAS28-ESR values and tear film osmolarity (P = 0.016). Spearman correlation coefficients between osmolarity and CRP or RF were not significant (CRP: r = -0.104, P = 0.353; RF: r = 0.138, P = 0.226).

Tear film osmolarity highly correlates with a modified dry eye severity scale in patients with RA with previously unknown DED. Tear film hyperosmolarity >316 mOsmol/L is correlated significantly with a commonly used DAS of RA (DAS28-ESR) but not with serum markers such as CRP and RF. Patients with RA with a high DAS28-ESR score show higher prevalence of tear film hyperosmolarity.