Acanthamoeba Keratitis:
What Contact Lens Wearers Need To Know

Acanthamoeba eye infections among contact lens wearers are rare but serious, which means that good hygiene is very important when it comes to handling lenses properly.

Contact lens wearers should follow wearing and cleaning instructions from both manufacturers and eye doctors very closely, to reduce the possibility of ever having this type of eye infection.

Prevention is always the best approach, because Acanthamoeba keratitis can be extremely difficult to treat — sometimes requiring a corneal transplant.

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

If these parasites infect the eye, an unusual but sight-threatening condition called Acanthamoeba keratitis results.

The condition first was diagnosed in 1973, with about 90 percent of cases involving contact lens wearers. But overall the risk of Acanthamoeba keratitis typically is quite low, with only about two cases reported per million contact lens wearers.

In recent years, however, the U.S. Centers for Disease Control (CDC) and other researchers have noted certain, sometimes isolated instances of higher numbers of Acanthamoeba keratitis cases among contact lens wearers.

As an example, the CDC in 2007 released several public health warnings regarding the eye infection in association with use of the contact lens solution Complete MoisturePlus, manufactured by Advanced Medical Optics or AMO.

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 marketplace.

The contact lens solution itself was not contaminated, but it appeared to demonstrate ineffectiveness in preventing Acanthamoeba keratitis. [Read more about fungal eye infections associated with use of another contact lens solution.]

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. 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 keratitis cases with the introduction of lens care systems that do not fully emphasize the need to clean contact lenses upon removal.

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.

Symptoms of Acanthamoeba keratitis include redness 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. Keep in mind, though, that Acanthamoeba keratitis is often difficult for your eye doctor to diagnose at first because its symptoms appear similar to those associated with other eye infections.

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

Unfortunately, in most cases of Acanthamoeba keratitis, permanent vision loss occurs. Once you have this type of eye infection, the CDC says that corneal transplant surgery often is necessary to recover lost vision.

There are a number of easy ways to greatly reduce the chances you will acquire this sight-threatening condition — and, in fact, any type of eye infection:

1. Follow your eye doctor's recommendations regarding care of your contact lenses. Use only products that your practitioner recommends.
    
2. Never use tap water with your lenses, and do not swim, shower or use a hot tub while wearing your contact lenses. If you do decide to wear your lenses while swimming, wear airtight swim goggles and afterward dispose of the lenses immediately.
    
3. Be sure to soak your lenses in fresh disinfecting solution every night. Use of a wetting solution or a saline solution not intended for disinfection is not recommended.
    
4. Always wash your hands before handling your lenses.
    
5. Unless you are wearing disposable contact lenses that are replaced daily, always clean the lenses upon removal, or at a minimum, rub the lenses with your multipurpose solution and rinse the solution off of the lens.

Also remember that cleanliness and proper care are equally important for contact lens cases.

Besides using good hygiene in the wear and handling of contact lenses, you also should consider cleaning and sterilizing lens cases to avoid Acanthamoeba contamination.

Many practitioners recommend, at a minimum, cleaning your contact lens case with hot tap water and leaving it out to air dry when not in use.

Replace your case at least every three months, and preferably every month.

If you want to take extra precautions or do a more thorough cleaning, scrub your case with a clean toothbrush, rinse with sterile, disinfecting solution and then allow it to air dry.

The case can be sterilized weekly, either by boiling it in hot water or microwaving it (in dry form) for three minutes.

Again, remember that 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.