Conjunctival impression cytology versus routine tear function tests for dry eye evaluation in contact lens wearers

AIMS: Prolonged contact lens wear is often accompanied by dryness of the eyes. The aim of this study was to compare conjunctival impression cytology (CIC) and tear film tests such as tear film break up time (TBUT) and Schirmer test for dry eye evaluation in contact lens wearers and measure their correlation with dry eye symptoms. SETTING: A case control study was done at three referral eye centers. MATERIALS AND METHODS: The eyes of 230 contact lens users were compared to 250 eyes of age- and sex-matched controls. Participants were recruited based on their response to a questionnaire of dry eye symptoms, (Dry Eye Scoring System, DESS(©)) and measurements of TBUT, Schirmer test, and CIC was done. A correlation analysis between symptom severity and tear film tests was performed. Pearson's coefficient, R(2) > 0.5 was considered significant. RESULTS: As compared to controls (r(2) = 0.010), Nelson grade correlated significantly with dry eye symptoms (r(2) = 0.765), among cases. However, there was moderate correlation between dry eye symptoms, Schirmer test, and TBUT (r(2) = 0.557 and 0.530, respectively) among cases and a weak correlation among controls (r(2) = 0.130 and 0.054, respectively). The sensitivity of TBUT was 86.4%, specificity was 82.4%, positive likelihood ratio (LR) was 4.50 [95% confidence interval (CI) 3.46-5.85)], and negative LR was 0.09. The sensitivity of the Schirmer test was 48.2%, specificity 88%, LR 2.12 (95% CI 1.48-2.96), and negative LR 0.83. CONCLUSION: CIC correlates better than Schirmer and TBUT with dry eye symptoms. It may be the most appropriate test for dry-eye evaluation in contact lens wearers.