Ocular surface assessment in soft contact lens wearers; the contribution of tear osmolarity among other tests

Purpose: To determine whether tear osmolarity contributes to the assessment of the ocular surface in soft contact lens (CL) wearers. Methods: Prospective, case-control series in 44 CL wearers (28 tolerant and 16 intolerant) and 34 healthy subjects. Every patient underwent a thorough ophthalmic examination with a tear osmolarity test (TearLab System), conjunctival impression cytology and meibomian lipid sampling. Symptoms, break-up time (BUT), tear osmolarity, conjunctival expression of HLA-DR and meibomian fatty acid composition were evaluated. Results: Tear osmolarity did not differ between controls and CL wearers (p=0.23). Flow cytometry results expressed in antibody-binding capacity (ABC) units and percentage of positive cells revealed a significant difference between the intolerant CL wearer group and the control group (p<0.0001). Comparisons between tolerant and intolerant CL wearers showed only a significant difference for mean fluorescence levels expressed in ABC units (p<0.0001). The BUT was significantly shorter in intolerant and tolerant CL wearers subjects than in healthy subjects (p<0.0001), whereas there was no significant difference in meibomian fatty acid composition (p=0.99) between the two groups. Conclusion: Contact lens wear is responsible for ocular surface alterations whose patterns are very similar to those reported in early dry-eye syndrome. However, tear osmolarity was not modified in these selected CL wearers. The yield of tear osmolarity with TearLab (TM) in assessing ocular surface disorders in CL wearers deserves further investigation.