Poor contact lens storage case hygiene significantly increases risk of microbial keratitis

This prospective, case-control study found that moderate and severe microbial keratitis associated with daily wear contact lens (CL) use was independently associated with factors likely to cause contamination of CL storage cases. These include frequency of storage case replacement, hygiene and solution type used. Other factors included occasional overnight use of CLs, smoking and higher socioeconomic class. The authors conclude that disease load may be considerably reduced by attention to modifiable risk factors related to CL storage case practice.

The investigators identified new cases of moderate and severe microbial keratitis in daily CL users presenting in Australia over a 12-month period. Controls were daily CL users in the community identified using a national telephone survey. The results were based on telephone interviews with 90 cases and 1,090 controls.

The authors found that independent risk factors for moderate and severe keratitis, adjusting for age, gender and lens material type, included poor storage case hygiene (failure to air dry), infrequent storage case replacement (less than every six months), solution type (multipurpose solution A, a no-rub multipurpose solution containing 0.0001% polyhexamethyl biguanide, poloxamer 237 [Pluronic 87] and ethyldiamine tetra-acetic acid) , occasional overnight lens use (< 1 night per week), high socioeconomic status, and smoking.

The authors say that proper storage case hygiene, which requires air drying after each use, could eliminate about half of all moderate and severe microbial keratitis cases. Alternatively, daily disposable CLs do not require the use of a storage case and could eliminate this risk factor.

They say that the association found in this study between higher socioeconomic class and moderate and severe microbial keratitis was unexpected and remains unexplained. Perhaps this is attributable to some attitude or behavior not examined in this study.