Shedding New Light on a Potentially Blinding Eye Infection

To See or Not to See

Allison C. Brown, PhD, MPH


August 27, 2012

Editorial Collaboration

Medscape &

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Hello. I'm Dr. Allison Brown, an epidemiologist with the Waterborne Disease Prevention Branch at the Centers for Disease Control and Prevention (CDC). I am here today as part of the CDC Expert Commentary Series on Medscape.

I would like to speak with you about Acanthamoeba keratitis, otherwise known as "AK." AK is a rare but potentially blinding eye disease caused by Acanthamoeba, a parasitic, free-living amoeba commonly found in water and soil. Approximately 85% of AK cases in the United States occur in contact lens wearers.[1,2]In a nationwide investigation of AK cases from 2008 to 2011, we found that 93% of case patients were contact lens wearers and that poor contact lens hygiene was the most significant risk factor for infection. According to our data, nearly 70% of contact lens-wearing case patients reported "topping off," which we defined as adding fresh lens solution to previously-used solution in the contact lens case. This behavior was associated with a risk for infection that was 4 times higher than the risk for contact lens wearers who did not top off. Additional risk factors for infection included: storing lenses in water, wearing lenses for fewer than 12 hours at a time, having worn contact lenses for fewer than 5 years, and being younger than 26 years of age or older than 55 years of age.

CDC encourages eye care providers to inform their contact lens-wearing patients about the risk for AK associated with improper contact lens hygiene practices and recommends that patients contact their eye care provider if they experience symptoms of eye irritation or infection.

CDC has developed 4 key messages that eye care providers can give patients, and parents of young patients, about contact lenses safety:

1. You have only 1 set of eyes so treat them with care. Reduce the risk for AK and other eye infections by following all eye care professional and manufacturer guidance for cleaning, storage, and use of contact lenses and contact lens cases.

2. Do not "top off" the solutions in your lens case. In other words, don't ever reuse any lens-disinfecting solution. Instead, always discard all leftover solution after each use. Used lens solution can be contaminated with bacteria and amoebas. In addition, used solution is not as effective at disinfecting lenses.

3. Be sure to clean, rub, and rinse your lenses, and air-dry your lens case each time you remove your lenses from the case. Rubbing and rinsing your contact lenses with disinfecting solution will aid in removing microbes and residues, including biofilms, which are slimy build-ups of bacteria and mold that can cause eye infections like AK.[3,4] In addition, recent studies indicate that dried films of disinfection solutions may harbor Acanthamoeba that are more resistant to disinfection. Thus, ideally, lens cases should be replaced at least every 3 months.[5,6]

4. Try to avoid exposing your contact lenses to any water. Do not rinse or store your lenses in water. Minimize contact lens exposures to tap water in the bathroom and kitchen as well as to recreational water in swimming pools, hot tubs, lakes, rivers, and oceans.

The recent CDC investigation of AK also indicated that there is a substantial delay from symptom onset to diagnosis of AK, and that this delay is strongly associated with poorer clinical outcomes, including clinical blindness and the need for corneal transplants. To help reduce the risk for delayed diagnosis, encourage your patients to contact you if they experience eye irritation or symptoms of eye infection. CDC also recommends that you consider AK among your differential diagnoses when evaluating patients -- including those who don't wear contact lenses -- who report symptoms such as eye pain, redness, blurred vision, and photophobia.

You will find additional information on AK and contact lens care practices on this page. I hope you are able to use these resources in your everyday practice to improve your patients' knowledge of AK and increase their adherence to recommended contact lens hygiene practices.

Thank you.

Web Resources

For Health Professionals

CDC. Acanthamoeba

CDC Acanthamoeba Keratitis Fact Sheet

CDC. Images of Acanthamoeba Keratitis

The Medical Letter: Treatment Recommendations: Acanthamoeba Keratitis

CDC. Additional publications on Acanthamoeba and Acanthamoeba keratitis

For Contact Lens Wearers

American Academy of Ophthalmology. Proper Care of Contact Lenses

FDA. Important Contact Lens Care Tips

CDC. Contact Lens Care

CDC. Vision Health Initiative (information about common eye disorders)

Allison C. Brown, PhD, MPH, is an epidemiologist with the US Centers for Disease Control and Prevention, Division of Foodborne, Waterborne, and Environmental Diseases. While training in CDC's Epidemic Intelligence Service, her work involved epidemiologic research, prevention, and education related to foodborne and waterborne diseases, such as salmonellosis, cholera, cryptosporidiosis, primary amebic meningoencephalitis, and Acanthamoeba keratitis. Dr. Brown is now assigned to the Enteric Diseases Epidemiology Branch at the CDC, where she focuses on surveillance and epidemiology of antimicrobial resistance among enteric bacteria of humans and food-producing animals. Dr. Brown holds a PhD in molecular microbiology and immunology from The Johns Hopkins Bloomberg School of Public Health and an MPH in Epidemiology from Yale University.