The epidemic of Acanthamoeba keratitis: where do we stand?

PURPOSE: To review from a historical perspective the recent epidemic of Acanthamoeba keratitis and its association with the use of contact lenses and to provide a summary of recent techniques that have allowed earlier diagnosis and treatment.

METHODS: The authors reviewed available literature on Acanthamoeba keratitis from 1973 to the present, with emphasis on the history of the epidemic and its association with contact lenses, identification of risk factors, preventive measures, and current diagnostic techniques. We also estimated the annual incidence of Acanthamoeba keratitis during 1985 through 1987 from available data.

RESULTS: Before the popularization of soft-contact-lens wear, Acanthamoeba keratitis was extremely rare; however, an epidemic began in the early 1980s, and the number of cases increased dramatically beginning in 1984. By 1985, the association of this infection with the use of contact lenses was firmly established, and in 1987, the infection was shown to occur more commonly among men, as well as in contact-lens wearers who failed to disinfect their lenses as frequently as recommended, swam while wearing lenses, or used homemade instead of commercially prepared saline solution. Adoption of "disposable" contact lenses in the late 1980s did not decrease the risk of Acanthamoeba keratitis, and concerns remain regarding the effectiveness of some contact-lens disinfectants; however, recent advances in diagnosis and treatment have improved the prognosis. The annual incidence during 1985 through 1987 was conservatively estimated at 1.65 to 2.01 cases per million contact-lens wearers. It is unclear whether the incidence is declining.

CONCLUSION: Acanthamoeba keratitis has now been recognized worldwide, and there are clear associations of this infection with improper contact-lens hygiene, particularly contact with water. Recent methods allow earlier diagnosis and thus improved outcomes. The epidemic provides a valuable lesson on how a new technology can be associated with unforeseen complications and exemplifies how rapid dissemination of epidemiologic information can aid in controlling an emergent epidemic.