The Contact Lens and Dry Eye Study (CLADES) is a cross-sectional/nested case-control study designed to study tear film, contact lens, ocular surface, and patient-related factors associated with self-reported dry eye disease in contact lens wearers. Data from 325 patients in the CLADES database were used for these analyses. Two datasets were assembled in order to determine tear film, contact lens, and patient-related factors associated with self-reported dry eye. The full dataset (n = 325) includes all patients in the original dataset and the clean dataset (n = 216) includes only patients who completed the CLDEQ on two occasions and who did not misclassify their disease status upon re-administration of the survey.
Factors that contributed significantly to the prediction of disease status across both the full and clean datasets included gender (p < 0.0001 and 0.006, respectively) and meibomian gland count (p = 0.02 and 0.03, respectively). However, the result for meibomian gland count was opposite of what was expected (e.g., more whole glands counted was associated with dry eye disease). Other factors that showed significance in the analysis of the clean dataset included osmolarity (p = 0.02), nominal water content (p = 0.03), and pre-lens tear film noninvasive breakup time (p = 0.03). No analyses showed a relation between measured dehydration and dry eye status, either when grouped together, or for specific contact lens types.
In summary, classification issues relating to contact lens-related dry eye studies significantly impact the internal validity of the sample, and these data provide some initial insight into these issues. Several factors were found to be associated with contact lens-related dry eye including gender (females), increased osmolarity, and decreased pre-lens non-invasive breakup time. The data are not consistent with the hypothesis that contact lens wear leads to alterations of meibomian gland structure. Yet, contact lens wear seems to alter the pre-lens lipid layer in a way that was not measured by the outcomes of this study. Future studies will need to address alternative hypotheses as they relate to the pre-lens tear film and dry eye during contact lens wear.