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Amebic Keratitis

By Richard D. Pearson, MD, Emeritus Professor of Medicine, University of Virginia School of Medicine

Amebic keratitis is a rare infection of the cornea caused byAcanthamoebaspecies. It usually occurs in people who wear contact lenses.

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 scraped.


Typically, painful sores develop on the cornea. Symptoms include eye redness, excess tear production, sensation of a foreign body, and pain when the eyes are exposed to bright light. Vision is usually impaired.


  • Examination and culture of a sample taken from the cornea

For diagnosis, 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. They should not use a homemade solution. Also, people should not wear contact lenses while swimming, in hot tubes, or during showers.


  • Antimicrobial drugs

Early, superficial infection can be treated more easily. If sores are superficial, doctors use a cotton-tipped applicator to remove infected and damaged cells. A combination of two or more antimicrobial drugs, such as polyhexamethylene biguanide (used to disinfect contact lenses) plus propamidine (applied topically), works best. They are applied every hour or two for the first 3 days. Other drugs applied topically (such as the antifungal drug miconazole or the antibiotic neosporin) are sometimes also used.

Fluconazole or itraconazole (antifungal drugs) may be taken by mouth, particularly if the infection is severe. Treatment is intensive the first month, then gradually decreased as healing occurs. Treatment often lasts 6 to 12 months. If treatment is stopped too soon, the infection is likely to recur.

Surgery to repair the cornea (keratoplasty) is rarely needed unless diagnosis and treatment are delayed or drug treatment is ineffective.

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