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Acanthamoeba Keratitis: What Contact Lens Wearers Need To Know

Acanthamoeba eye infections in contact lens wearers are rare but serious, and they often start because of improper lens handling and poor hygiene.


Red eye affected by advanced acanthamoeba keratitis.
Advanced Acanthamoeba keratitis can cause a white "ring" to cover the iris, as well as redness in the white of the eye. (Also read about conjunctivitis, another cause of eye redness.) [Enlarge]

To avoid Acanthamoeba keratitis, be sure to carefully follow the lens care, handling and wearing instructions you receive from your eye doctor.

Proper contact lens care greatly reduces the risk of all contact lens-related eye infections, including those caused by Acanthamoeba.

Prevention is always the best approach, because Acanthamoeba keratitis can be extremely difficult to treat; in fact, sometimes these infections require a corneal transplant, which is a serious surgical procedure.

What Are Acanthamoeba?

Acanthamoeba are naturally occurring amoeba (tiny, one-celled animals) commonly found in water sources, such as tap water, well water, hot tubs, and soil and sewage systems.

If these tiny parasites infect the eye, Acanthamoeba keratitis results. The condition was first diagnosed in 1973, with about 90 percent of cases involving contact lens wearers.

Acanthamoeba Outbreaks Among Contact Lens Wearers

In recent years, the U.S. Centers for Disease Control and Prevention (CDC) and other researchers have noted sporadic outbreaks of Acanthamoeba keratitis cases among contact lens wearers.

For example, in 2007 the CDC released several public health warnings regarding Acanthamoeba keratitis associated with use of the contact lens solution Complete MoisturePlus, manufactured by Abbott Medical Optics (AMO) — formerly Advanced Medical Optics.

The CDC said a sevenfold increase in the risk of developing Acanthamoeba keratitis associated with use of the contact lens solution prompted AMO to withdraw Complete MoisturePlus from the market. The contact lens solution itself was not contaminated, but it seemed to be ineffective in preventing Acanthamoeba keratitis.

The CDC has issued similar warnings concerning fungal eye infections associated with the use of Bausch + Lomb's ReNu With MoistureLoc contact lens solution, which was removed from worldwide markets in May 2006.

What Causes Acanthamoeba Keratitis?

Factors and activities that increase the risk of contracting Acanthamoeba keratitis include using contaminated tap or well water on contact lenses, using homemade solutions to store and clean contacts, wearing contact lenses in a hot tub and swimming or showering while wearing lenses.

Amoeba
Acanthamoeba is a single-cell organism that exists in nature in two forms: an active, growing form (left) and a dormant, stress resistant cyst (right). (Images: Jacob Lorenzo-Morales, Naveed A. Khan and Julia Walochnik [CC BY 2.0], via Wikimedia Commons) [Enlarge]

A dirty lens case also can be a source of Acanthamoeba infection.

In addition, some scientists theorize that new U.S. Environmental Protection Agency regulations aimed at reducing carcinogenic (potentially cancer-causing) products such as disinfectants in the water supply may have inadvertently boosted microbial risks, including an increased likelihood of finding Acanthamoeba in water supplies.

Other researchers associate recent increases in contact lens-related eye infections with the introduction of "no-rub" lens care systems that may result in less effective contact lens cleaning and disinfection.

But regardless of the cause of the increase, Acanthamoeba can be killed easily, especially when rubbed off the lens surface during cleaning. In the end, good contact lens hygiene is the best way to prevent Acanthamoeba keratitis.

How Do You Know if You Have Acanthamoeba Keratitis?

Symptoms of Acanthamoeba keratitis include red eyes and eye pain after removing your contact lenses, as well as tearing, light sensitivity, blurred vision and a feeling that something is in your eye.

With these types of symptoms, you should always contact your eye doctor. But keep in mind that Acanthamoeba keratitis is often difficult for your eye doctor to diagnose at first, because its symptoms are similar to pink eye symptoms and those of other eye infections.

Diagnosis of keratitis often occurs once it is determined that the condition is resistant to antibiotics used to manage other infections. A "ring-like" ulceration of your corneal tissue may also occur.

Unfortunately, if not promptly treated, Acanthamoeba keratitis can cause permanent vision loss or require a corneal transplant to recover lost vision.

How Can You Reduce the Risk of Getting Acanthamoeba Keratitis?

There are several easy ways to greatly reduce the chance of getting this sight-threatening condition — and, in fact, any type of contact lens-related eye infection:

Contact lens in case.
Remember to also clean and sterilize your lens cases, to avoid Acanthamoeba contamination.
  1. Follow your eye doctor's recommendations regarding care of your contact lenses. Use only products that he or she recommends.
  2. Never use tap water with your contact lenses. The FDA has recommended that contact lenses should not be exposed to water of any kind.
  3. Do not swim, shower or use a hot tub while wearing contacts. If you do decide to wear your lenses while swimming, wear airtight swim goggles over them. (Read about additional strategies for swimming with contact lenses.)
  4. Be sure to soak your lenses in fresh disinfecting solution every night. Don't use a wetting solution or saline solution that isn't intended for disinfection.
  5. Always wash your hands before handling your lenses.
  6. Unless you are wearing disposable contact lenses that are replaced daily, always clean your contacts immediately upon removal, rubbing the lenses under a stream of multipurpose solution — even if using a "no-rub" solution — and storing them in a clean case filled with fresh (not "topped off") multipurpose or disinfecting solution.

Take Care of Your Contact Lens Case

Cleanliness and proper care are equally important for contact lens cases.

It's important to clean, rinse and air-dry your contact lens case immediately after removing your lenses from the case. Discard the old solution and rub the inside wells of the case with clean fingers for at least five seconds. Then fill the case with multipurpose solution or sterile saline (not tap or bottled water), dump this out, and store the case upside down with the caps off.

As an extra precaution, you might want to consider sterilizing your empty contact lens case once a week by submerging it in boiling water for a few minutes.

Many eye doctors also say you should discard and replace your contact lens case monthly or, at a minimum, every three months to help prevent contamination.

Again, prevention is your best defense against Acanthamoeba keratitis. Always use good hygiene during contact lens use and care. And if you notice any unusual eye symptoms that might indicate an infection, immediately consult your eye doctor.

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Page updated May 14, 2018

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