Risk factors for contact lens-related microbial keratitis in Singapore

Purpose: To investigate independent risk factors for contact lens-related microbial keratitis in Singapore and estimate their impact on disease load. Methods: Cases were contact lens wearers presenting to Singapore National Eye Centre with microbial keratitis between 2008 and 2010. Community contact lens wearers were recruited 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 in a multivariate model. Results: In all, 58 cases of microbial keratitis and 152 contemporaneous controls were identified. When controlling for other variables, Chinese had a 7 x lower risk compared with other races (95% CI: 2.3-21.3, P=0.001). Those aged between 25 and 44 years were at 3x increased risk compared with younger wearers (95% CI: 1.1-9.6, P=0.04). Occasional overnight contact lens wear (less often than one night per week) was associated with a 4x higher risk (95% CI: 1.2-15.4, P=0.03) compared with daily use. Not washing hands before handling was associated with a 13x increased risk (95% CI: 1.9-84.8, P=0.008). Use of multipurpose solution A carried a 16x higher risk compared with hydrogen peroxide (95% CI: 1.5-174.0, P=0.02). The combined PAR% for modifiable risk factors (occasional overnight wear, not washing of hands, and MPS A) was 82%. Conclusions: Consistent with previous findings, independent risk factors for contact lens-related microbial keratitis include poor hand hygiene, occasional overnight wear, and type of lens care solution. Prolonged overnight or extended contact lens use was infrequent in this population.