Tear film osmolarity in ocular mucous membrane pemphigoid

PURPOSE: The aim of this study was to evaluate tear film osmolarity in patients with ocular mucous membrane pemphigoid (MMP). METHODS: This observational cross-sectional study included 40 patients with biopsy-proven ocular MMP at Foster stage III referred to the tertiary-care Ocular Immunology and Uveitis Service at the San Raffaele Scientific Institute in Milan from June 2010 to August 2013. We evaluated the following clinical parameters: tear film osmolarity, ocular surface disease symptoms (OSDI) questionnaire, Schirmer test, tear film break-up time (TFBUT), and corneal and conjunctival staining. RESULTS: Forty patients (27 women and 13 men) were enrolled. All patients were undergoing systemic immunosuppressive therapy: 19 patients (47.5%) were on methotrexate, 9 (22.5%) were on mycophenolate mofetil, 9 (22.5%) were on low-dose corticosteroids, and 3 (7.5%) were on azathioprine. The mean osmolarity was 322.90 ± 33.39 mOsm/L, the mean OSDI score was 73.2 ± 17.9, the mean TFBUT was 6.60 ± 3.13 seconds, and the mean Schirmer test value was 4.07 ± 3.58 seconds. Tear film osmolarity significantly correlated with the TFBUT (r = 0.80; P <0.0001), whereas no clinical correlation was found with the Schirmer test value (r = 0.01; P = 0.40) or with the OSDI score (r = 0.02; P = 0.29). Osmolarity did not turn out to be statistically different in the subgroups according to the Oxford corneal staining scale (P = 0.71) and to the Van Bijsterveld conjunctival staining score (P = 0.31). CONCLUSIONS: Tear osmolarity increased in patients with ocular MMP and correlated with the TFBUT. This result emphasizes the role of evaporative dry-eye condition in patients with ocular MMP. Tear osmolarity may be considered as a useful test in the diagnostic assessment of dry eye associated with MMP and for targeting therapeutic decisions.