Amebic keratitis (eye infection)

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Amebic keratitis is a rare infection of the cornea (the clear layer in front of the iris and pupil of the eye) caused by Acanthamoeba species, free-living amebas. It usually occurs in people who wear contact lenses.

Amebic keratitis causes painful sores on the cornea, and vision is usually impaired.
Doctors take a sample of tissue from the cornea to be examined and cultured.
To help prevent this infection, people should keep their contact lens in a sterile solution and should not wear contact lenses while swimming, in hot tubs, or when taking a shower.
Eye doctors remove infected and damaged cells if sores are superficial and treat the infection with biguanide-chlorhexidine or polyhexamethylene biguanide (used to disinfect contact lenses) eye drops plus either propamidine or hexamidine eye drops.

(See also Overview of Parasitic Infections.)
Free-living amebas are protozoa that live in soil or water and do not need to live in people or animals. Although they rarely cause human infection, certain types of these amebas can cause serious, life-threatening diseases.
Amebic keratitis may be progressively destructive. Most (85%) infected people wear contact lenses. Infection is more likely if lenses are worn during swimming or if the lens cleaning solution used is unsterile. Some infections develop after the cornea is accidentally scraped.