Acanthamoeba Keratitis

Acanthamoeba keratitis is a rare, serious eye infection caused by an amoeba (tiny microorganism). It’s most common in people who wear contact lenses, but anyone can get the infection. It can lead to vision loss or total blindness without prompt treatment.


What is acanthamoeba keratitis?

Acanthamoeba keratitis is a serious infection that affects the cornea (clear outer covering of the eye). It’s caused by an amoeba, which is a tiny, single-celled organism. The amoeba enters your eye and eats through the layers of your cornea. It destroys tissue as it moves through your eye. The acanthamoeba is common in the air, soil, lakes and oceans. Most infections come from fresh water, such as tap water, swimming pools, hot tubs, showers and sewage systems.

Acanthamoeba keratitis is rare, but it can lead to eye pain, permanent vision loss or even total blindness. The infection can affect one or both eyes. It’s not contagious.


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Who is at risk of getting acanthamoeba keratitis?

Anyone can get acanthamoeba keratitis, but it’s most common in people who wear soft contact lenses. You have a greater risk of this condition if you:

  • Clean your contact lenses with tap water or saline instead of disinfectant solution.
  • Come into contact with water that contains the amoeba.
  • Don’t store and handle your contact lenses properly.
  • Have had past damage to your cornea.
  • Swim, shower or use a hot tub while wearing contact lenses.

How common is acanthamoeba keratitis?

Acanthamoeba keratitis is rare. In the US, only one to two people per million contact lens wearers develop the condition each year. It’s even more rare in people who don’t wear contact lenses.


Symptoms and Causes

What causes acanthamoeba keratitis?

The acanthamoeba causes this eye infection. The amoeba attaches to the cells on the outer surface of your cornea. It can also invade the eye by entering through small corneal abrasions (scratches). The infection destroys the cells and moves further into the cornea.

What are the symptoms of acanthamoeba keratitis?

Symptoms of early-stage acanthamoeba keratitis may include:

  • Blurred vision or vision loss.
  • Cloudy or dirty-looking cornea.
  • Eye pain.
  • Eye redness.
  • Sensation of something in the eye.
  • Sensitivity to light.
  • Watery eyes.
  • Whitish rings on the surface of the eye.

It can take several days to several weeks for symptoms to show up after the acanthamoeba enters your eye.


What are the complications of acanthamoeba keratitis?

Left untreated, the infection can cause permanent vision loss or total blindness. Other complications of late-stage acanthamoeba keratitis may include:

  • Anterior uveitis (inflammation in the uvea, or middle layer of the eye).
  • Iris atrophy (displaced pupil).
  • Mature cataracts (clear lens of eye is completely clouded).
  • Scleritis (inflammation of the sclera, or white part of the eye).
  • Secondary glaucoma (optic nerve damage).

Diagnosis and Tests

How is acanthamoeba keratitis diagnosed?

A healthcare provider specializing in eye care, such as an optometrist or ophthalmologist, can diagnose acanthamoeba keratitis. They perform an eye exam, review your symptoms and assess your contact lens hygiene (if you wear contacts).

It’s easy to misdiagnose this infection because the symptoms are similar to those of other corneal diseases. So, it’s very important to tell your healthcare provider if you’ve been in contact with any potentially contaminated water or other substances.

Tests for acanthamoeba keratitis may include:

  • Corneal scraping: Also called superficial keratectomy, corneal scraping is a procedure to remove cells from the surface of your cornea. Your healthcare provider numbs the surface of your eye and uses a small blade or brush to remove cells. They study the cells under a microscope or perform laboratory tests on the cells to check for infection.
  • Confocal microscopy: This exam uses laser light to create highly detailed images of every layer in your cornea. Your healthcare provider uses a special microscope to see corneal cells, nerves and any parasites, such as the acanthamoeba.

Management and Treatment

How is acanthamoeba keratitis treated?

A topical antiseptic is the most common treatment for acanthamoeba. The antiseptic fights microorganisms. It’s applied directly to the surface of your eye. You may need these treatments for six months to a year. Sometimes your healthcare provider scrapes off some of your cornea before applying medication. This helps the medicine get deeper into your eye.

Your healthcare provider may also recommend antibiotics or antifungal medications. Steroids or pain relief medications can help reduce pain and inflammation.

You may need surgery for advanced acanthamoeba keratitis that doesn’t improve with topical therapy. This may include penetrating keratoplasty (PK). A PK is a full-thickness corneal transplant. A cornea from a donor replaces your damaged cornea.


How can I prevent acanthamoeba keratitis?

You can reduce your risk of acanthamoeba keratitis by:

  • Avoiding contact with contaminated water, which could include freshwater lakes, rivers and hot springs.
  • Filling your contact lens storage case with fresh solution each time you open it.
  • Never sleeping in your contact lenses.
  • Not showering, swimming or using a hot tub while wearing contact lenses.
  • Not using another person’s contact lenses.
  • Replacing contact lenses regularly, according to your healthcare provider’s recommendations.
  • Using only disinfecting solution (not saline solution) to rinse and store your contact lenses — never use tap water.
  • Visiting your optometrist or ophthalmologist for regular exams.
  • Washing your hands before touching your eyes or handling your contact lenses.

Outlook / Prognosis

What is the outlook for people with acanthamoeba keratitis?

The earlier you receive a diagnosis and treatment for acanthamoeba, the better your outlook. Research suggests that people who seek treatment at the first signs of infection are 10 times more likely to recover with vision of 20/25 (mild vision loss) or better. The outlook is poor if the infection is already in the deep parts of the eye.

If you do experience vision loss from this infection, there are a variety of ways you can find support. You may be able to better cope with vision loss by:

  • Asking your healthcare provider about low-vision aids such as telescopic glasses or hand magnifiers.
  • Seeking counseling if you feel depressed or overwhelmed.
  • Talking with loved ones and caregivers about your condition.

Living With

When should I call the doctor?

Contact your healthcare provider at the first signs of eye pain, redness or sensitivity. Don’t wait until you experience vision loss.

What questions should I ask my doctor?

You may want to ask your healthcare provider:

  • How can I manage symptoms during treatment?
  • How far into the eye is the infection?
  • Should I expect complications?
  • Should I watch for signs of complications?
  • What are the chances I’ll lose my vision?

A note from Cleveland Clinic

Acanthamoeba keratitis is a rare, serious eye infection caused by a tiny organism that lives in fresh water. Anyone can get the infection, but it’s more common in people who wear contact lenses. Symptoms can range from eye pain and redness to blindness. Early detection and treatment greatly improve the outlook for people with this infection.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 05/25/2021.

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