Contact lens-related microbial keratitis: Part I: Epidemiology

To put into perspective the individual risk and the societal burden of contact lens microbial keratitis.

I reviewed the available epidemiologic data on contact lens microbial keratitis with emphasis on distinguishing microbial from nonmicrobial keratitis, determining the incidence of the disease, the relative risk with different styles of contact lenses, and the risk factors.

Contact lens wear can be classified in multiple different ways (indications for wear, contact lens material, wearing schedule, and replacement schedule). Adverse effects of contact lens wear on the cornea have been documented by several studies. Distinction between aseptic and septic focal infiltrates is discussed. The incidence rates for bacterial microbial keratitis range from approximately two/10,000 per year for rigid contact lens, 2.2-4.1/10,000 per year for daily-wear soft contact lens, to 13.3-20.9/10,000 per year for extended-wear soft contact lenses. The risk with therapeutic contact lenses is much higher: approximately 52/10,000 per year. Comparative studies suggest that the relative risk of microbial keratitis is approximately 1 for rigid gas-permeable lenses (RGPs; the referent), 0.5-2.74 for polymethylmethacrylate (PMMA), 1.0-4.2 for daily-wear soft contact lenses, 2.7-36.8 for extended-wear soft contact lenses, and 13.0-13.3 for disposable soft contact lens wear. The most significant risk factors include overnight wear, smoking, male sex, and socioeconomic status.

There is a significant health concern for the 26 million wearers of contact lenses with some potentially modifiable risk factors. Identification of the risk factors and further studies of the pathogenesis allow contact lens manufacturers to direct research efforts and practitioners to provide better information and informed consent to patients.