Acanthamoeba keratitis

An infection of the eye that typically occurs in healthy persons and can result in permanent visual impairment or blindness.

Acanthamoeba keratitis

• Acanthamoeba is a microscopic, free-living ameba, or amoeba* (single-celled living organism)
• The ameba is found worldwide in the environment in water and soil.
• The ameba can be spread to the eyes through contact lens use, cuts, or skin wounds or by being inhaled into the lungs.
• Most people will be exposed to Acanthamoeba during their lifetime, but very few will become sick from this exposure.

Pathogenesis

The three diseases caused by Acanthamoeba are:

1. Acanthamoeba keratitis – An infection of the eye that typically occurs in healthy persons and can result in permanent visual impairment or blindness.
2. Granulomatous Amebic Encephalitis (GAE) – A serious infection of the brain and spinal cord that typically occurs in persons with a compromised immune system.
3. Disseminated infection – A widespread infection that can affect the skin, sinuses, lungs, and other organs independently or in combination. It is also more common in persons with a compromised immune system

Acanthamoeba keratitis

• Acanthamoeba keratitis, or AK, is a rare but serious infection of the eye that can cause permanent vision loss or blindness.
• This infection is caused by a tiny ameba (single-celled living organism) called Acanthamoeba.
• Acanthamoeba causes Acanthamoeba keratitis when it infects the cornea, the clear dome that covers the colored part of the eye

Symptoms and signs

• Sensation of something in the eye
• Eye pain
• Eye redness
• Blurred vision
• Sensitivity to light called photophobia
• Excessive tearing

If you experience any of these symptoms, remove your contact lenses (if you wear them) and call your eye doctor right away. AK is a rare condition, but if left untreated it can result in vision loss or blindness

Acanthamoeba keratitis

Epidemiology

• Acanthamoeba is very common in nature and can be found in bodies of water (for example, lakes and oceans) and soil.
• It can also be found in tap water, heating, ventilating, and air conditioning units, and whirlpools.
• Infection of the eye occurs when the Acanthamoeba organisms contained in water or contact lens solution enter the eye through small scrapes that can be caused by contact lens wear or other minor eye injuries.

Transmission

• The Acanthamoeba organism has to make contact directly with the eyes in order to cause AK, so this type of corneal infection cannot occur from drinking or inhaling water that has this ameba in it.
• AK cannot be spread from person to person.

Contact lens wearers

In the United States, an estimated 85% of AK cases occur in contact lens wearers. For people who wear contact lenses, the risk of getting Acanthamoeba keratitis is higher if they:

Acanthamoeba cysts in interference contrast microscopy

• Do not store or handle contact lenses properly.
  • This can include not washing hands before touching contact lenses, not rubbing and rinsing lenses after taking them out, and not storing them in the recommended contact lens solution.
• Do not disinfect contact lenses properly.
  • This can include using tap water to clean the lenses or lens case, or adding fresh solution to existing used solution in the case instead of using only fresh solution when storing contact lenses.
• Swim, use a hot tub, or shower while wearing lenses.
• Have a history of trauma to the cornea, such as a previous eye injury.

Acanthamoeba keratitis

Diagnosis

• Early diagnosis is important because early treatment can prevent AK infections from becoming more severe.
• The infection is usually diagnosed by an eye doctor based on symptoms, lab results from a scraping of the eye, and/or through a close-up eye exam that allows the eye doctor to see the ameba.

Treatment

• AK can be difficult to treat, and the best treatment regimen for each patient should be determined by an eye doctor.
• AK usually requires aggressive medical and surgical treatment.
• If you think that your eye may be infected with Acanthamoeba, see an eye doctor immediately.

Acanthamoeba

Prevention

• Don’t Sleep in Your Contact Lenses
• Wash Your Hands
• Dry your hands well with a clean cloth
• Keep contact lenses away from all water
• Properly Clean Your Lenses
• Rub and rinse your contact lenses with contact lens disinfecting solution
• Never use water or saliva—to clean them each time you remove them
• Don’t “top off” solution
• Use only the contact lens solution recommended by your eye care provider
• Take care of your contact lens case properly

Acanthamoeba keratitis Resources
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