Contact Lenses, Disinfectants, and Acanthamoeba Keratitis

Abstract

Publisher Summary The chapter introduces Acanthamoeba Keratitis as a small filose, free-living amoeba with a cyst stage with ostioles. Acanthamoeba species are voracious predators of various Gram-negative bacteria, cyanobacteria, and fungi. Species are cannibalistic or pathogenic and grows in axenic enrichment culture and on defined media. The chapter discusses its taxonomy and various strains and culture conditions. The chapter also discusses the infectious nature of the amoeba. Acanthamoeba species cause the disease of the central nervous system which occurs primarily among the immunosuppressed or chronically ill, particularly AIDS patients. Acanthamoeba keratitis occurs most commonly among healthy normal individuals and seems associated with the minor trauma to the eye that accompanies contact lens wear. Failure to comply with proper hygienic procedures for cleaning and disinfecting lenses appears to be the major factor in most contact-lens-related eye infections. Species of Acanthamoeba dwell in damp soils and upper zones of mud in rivers and lakes and in anthropogenic water reservoirs. Cysts and trophozoites are carried by humans and distributed by wind, water, and animals. Species of Acanthamoeba readily colonize surface biofilms in swimming pools, hot tubs, heating-, ventilation-, and air-conditioning systems, and domestic water taps and eye-wash stations. The chapter also discusses disinfecting methods such as isopropyl alcohol cleaning system an “O 2 conditioner” which can kill both cysts and trophozoites within 30 minutes of exposure. Various reports indicate that trophozoites adhere preferentially over cysts to contact lenses and that various species and strains differentially adhere to the four Food and Drug administration (FDA) hydrogel lens groups. Both cysts and trophozoites show greater adherence to the higher-water-content lenses. Fastidious cleaning and disinfection of contact lenses, with particular care in lens storage, are necessary in the control of Acanthamoeba keratitis .