Predictive factors of contact lens case contamination

PURPOSE: To examine the relationship between contact lens (CL) case contamination and various potential predictive factors. METHODS: 74 subjects were fitted with lotrafilcon B (CIBA Vision) CLs on a daily wear basis for 1 month. Subjects were randomly assigned one of two polyhexamethylene biguanide (PHMB) preserved disinfecting solutions with the corresponding regular lens case. Clinical evaluations were conducted at lens delivery and after 1 month, when cases were collected for microbial culture. A CL care non-compliance score was determined through administration of a questionnaire and the volume of solution used was calculated for each subject. Data was examined using backward stepwise binary logistic regression. RESULTS: 68% of cases were contaminated. 35% were moderately or heavily contaminated and 36% contained gram-negative bacteria. Case contamination was significantly associated with subjective dryness symptoms (OR 4.22, CI 1.37–13.01) (P<0.05). There was no association between contamination and subject age, ethnicity, gender, average wearing time, amount of solution used, non-compliance score, CL power and subjective redness (P>0.05). The effect of lens care system on case contamination approached significance (P=0.07). Failure to rinse the case with disinfecting solution following CL insertion (OR 2.51, CI 0.52–12.09) and not air drying the case (OR 2.31, CI 0.39–13.35) were positively correlated with contamination; however, did not reach statistical significance. CONCLUSIONS: Our results suggest that case contamination may influence subjective comfort. It is difficult to predict the development of case contamination from a variety of clinical factors. The efficacy of CL solutions, bacterial resistance to disinfection and biofilm formation are likely to play a role. Further evaluation of these factors will improve our understanding of the development of case contamination and its clinical impact.