[Risk factors for contact lens-related microbial keratitis: A multicenter case-control study].

PURPOSE: Currently, the most feared complication by ophthalmologists of contact lens (CL) wear is microbial keratitis (MK), even though its incidence remains low. It is also a significant financial burden for society. This study aimed to identify the risk factors for CL-related MK especially with regard to hygiene and pattern of use, in a large, prospective, multicenter, case-control study.

METHODS: A multicenter retrospective case-control study was designed. The CL-related MK subpopulation (case) was compared with healthy CL wearers (control) using a 52-item anonymous questionnaire designed to determine subject demographics, lens wear history, lens type and disinfection solution, fitting, patient education, hygiene and maintenance of contact lenses, and patient history. Univariate logistic regression analysis was performed to compare both groups.

RESULTS: The study included 497 cases and 364 controls. The risk factors associated with the greatest increased odds of CL-related MK were as follows: extended wear (OR=2.96 [1.65-5.33], P<0.001), occasional overnight lens use (OR=6.37 [4,55-8.90], P<0.001), fitting by an optician (OR=1.97 [1.38-2.83], P<0.001), absence of ophthalmologic exam (OR=6.56 [2-22], P<0.01) or no training in handling the contact lens (OR=4.47 [2.27-8.77], P<0.01), use of optician's disinfection solution (OR=5.55 [3.12-9.85], P<0.001), mixing solutions ("topping off") (OR=4.68 [2.73-8.04], P<0.001), no case replacement (OR=3.95 [2.28-6.82] P<0.01), no compliance with hygiene rules and smoking (OR=2.29 [1.67-3.14], P<0.01). The protective factors associated with the greatest reduction in OR were female gender (OR=0.49 [0.36-0.66], P<0.01), hypermetropia (OR=0.28 [0.16-0.48], P=0.01), rigid contact lens wear, fitting by an ophthalmologist, written and verbal instruction, and daily case maintenance.

CONCLUSION: The knowledge of these risks factors incentivizes action at all levels to reduce the incidence of MK, from the prescriber to the patient, including the type of CL, case and contact lens solution.