Differences in clinical parameters and tear film of tolerant and intolerant contact lens wearers

PURPOSE. To determine whether intolerance to contact lens wear is attributable to clinical or protein characteristics of the tear film. METHODS. Thirty-eight subjects participated; 20 were successful contact lens wearers and 18 had discontinued contact lens wear because of discomfort. Baseline tear film (no lens wear) was analyzed with a range of clinical measurements and protein analyses (lactoferrin, sIgA, and lysozyme). Comfort was determined after 6 hours of lens wear, and differences in tear film characteristics between subject groups were determined. In half of the subject group (n = 19), discriminant analysis was used to develop an equation for predicting the likelihood of intolerance to lens wear. Sensitivity and specificity were determined by testing the formula on the remaining subjects. These formulas were also tested on a separate group of subjects enrolled in a contact lens-wearing trial. RESULTS. Tear volume (meniscus height and phenol red thread test) and tear stability (noninvasive tear break up time [NI-TBUT]) were significantly reduced in intolerant wearers (P < 0.05). A greater number of symptoms were reported by intolerant than by tolerant wearers (P < 0.05). Tolerance was associated with clinical but not protein characteristics of the tear film. Formulas best able to predict contact lens intolerance included NI-TBUT, number of symptoms experienced, and tear film meniscus height. Formulas had high sensitivity, and specificity which ranged from 29% to 57%. CONCLUSIONS. Contact lens intolerance appears to be best predicted by a combination of clinical variables, including tear film stability, tear volume, and symptom reporting.