Purpose
Patterns of contact lens prescribing, wearer behavior and environmental microbiota vary across different cultures and climates, which may impact risks for microbial keratitis. This study investigates independent risk factors for microbial keratitis in contact lens wearers in Singapore.
Methods
Cases were contact lens wearers presenting to Singapore National Eye Centre with microbial keratitis between 2009-2010. Contact lens wearers attending for routine aftercare at a nearby University Clinic over the same time period were identified as controls. All wearers completed a previously validated questionnaire describing contact lens wear history, hygiene and compliance habits and demographics. Risk factors significant in univariate analysis (p<0.2) were evaluated using multiple binary logistic regression.
Results
Fifty eight cases of microbial keratitis and 152 contemporaneous controls were identified. When controlling for other variables, showering in lenses was associated with a 3x higher risk (95% CI 1.1-6.6). Washing and drying hands prior to handling was associated with an 8x lower risk (95% CI 1.3-47.6). Complete lens care solution (AMO, CA) had a higher risk compared to hydrogen peroxide and other multipurpose lens care solutions (OR 27.8 95% CI 2.5-333.3; OR 8.9, 95% CI 3.1-22.2, respectively). Chinese ethnicity had a 7x lower risk compared to other races (95% CI 2.3-18.7).
Conclusions
Consistent with previous findings, independent risk factors for contact lens related microbial keratitis included poor hand hygiene. Showering in lenses and type of lens care solution was also associated with increased risk in this population. A case control study of fungal keratitis in Singapore similarly found a lower risk for Chinese compared to Malays, similar to findings in this study. While this may be associated with socioeconomic factors, other behavioural and innate factors warrant further investigation.
Keywords: 477 contact lens