Acanthamoeba keratitis and contact lenses

If you wear contact lenses and think you take good care of them, ask yourself these questions:

  • Have you worn contacts while swimming or in a hot tub?
     
  • Do you rinse your contacts or your lens case with tap water?
     
  • Do you re-use solution or “top off” the solution in your lens case?

If you answered “yes” to any of these questions, you could be at risk of acquiring a potentially blinding eye infection.

What is acanthomoeba keratitis? ► What is acanthomoeba keratitis? ▼

Acanthamoeba keratitis is a severe, painful infection of the cornea, the transparent outer covering of the eye, which usually causes scarring and, if undiagnosed and untreated, can lead to blindness.  In the most severe cases, a corneal transplant is necessary.  The infection is believed to be caused through exposure of the eye to water contaminated with the amoeba Acanthamoeba, a free-living organism.

What are the risk factors for infection? ► What are the risk factors for infection? ▼

Individuals who wear contact lenses are at the highest risk for contracting the infection.  The two biggest risk factors are: poor lens hygiene and exposure to water while wearing lenses.

How can I avoid infection? ► How can I avoid infection? ▼

The single best way to avoid eye infections is to follow proper lens care guidelines as prescribed by your eye care professional.  The following are key tips for contact lens care:

  • Before handling contact lenses, wash your hands with soap and water, then rinse and dry them with a lint-free towel.
  • Minimize contact with water, including removing lenses before going swimming or in a hot tub.
  • Contact lenses should not be rinsed with or stored in water (tap or sterile water).
  • Wear and replace contact lenses according to the schedule prescribed by your eye care professional.
  • During cleaning, using fresh solution, rub your contact lenses with your fingers, then rinse the lenses with solution before soaking them – even if the solution you are using is a “no-rub” variety.
  • Contact lens cases should always be cleaned with fresh solution – not water. Then leave the empty case open to air dry.
  • Keep the contact lens case clean and replace it regularly, at least every three months.
  • Do not re-use old solution or “top off” the solution in your lens case.
  • Do not use cracked or damaged lens cases. Lens cases can be a source of contamination and infection.

Swimming and contact lenses ► Swimming and contact lenses ▼

If you must swim with your lenses or have contact with water, use daily disposables and throw the lenses out immediately afterward. The Federal Drug Administration (FDA) does not require that lens solutions be Acanthamoeba resistant so disinfecting them after exposure to water will not kill the organism if it is present.

How rare is acanthamoeba keratitis? ► How rare is acanthamoeba keratitis? ▼

If you must swim with your lenses or have contact with water, use daily disposables and throw the lenses out immediately afterward. The Federal Drug Administration (FDA) does not require that lens solutions be Acanthamoeba resistant so disinfecting them after exposure to water will not kill the organism if it is present.

Acanthamoeba keratitis is extremely rare in the United States. It was first recognized in 1973. Between 1973 and 1988, 208 cases were reported each year.  85% of those cases involved contact lens wearers. This translates to 1.65 to 2.01 cases per million contact lens wearers diagnosed nationally each year. 

The first outbreak was reported to the Centers for Disease Control and Prevention in the mid 1980’s, where 24 patients from 14 states were diagnosed with the bacteria.  The second largest was reported in 2007 with 46 confirmed cases in 35 states. Common cleansing products in these cases included: a homemade saline solution with salt tablets and non-sterile water, a commercially produced saline solution, as well as tap water.

In the Chicagoland area, 40 cases were diagnosed at the University of Illinois-Chicago between June 1, 2003 and November 30, 2005.

Infection and tap water ► Infection and tap water ▼

Researchers have begun to explore other possibilities outside of the most common risk factors. Because Acanthamoeba is a waterborne pathogen, one theory is local water supply contamination.  Recent changes in the United States Environmental Protection Agency (EPA Guidelines) regarding the chemical makeup and strength of water disinfection products may have a direct correlation to the proliferation of Acanthamoeba in certain geographic areas.  In order to reduce the number of byproducts in the water after the purification process, the EPA made changes to the concentrations and procedures which may not effectively kill this bacteria and other microorganisms.

Acanthamoebae are also resistant to killing by freezing, dessication, several varieties of antimicrobial agents, and levels of chlorine that are routinely used to disinfect drinking water, swimming pools and hot tubs.

Infection symptoms ► Infection symptoms ▼

Symptoms of an infection include redness, pain, tearing, increased light sensitivity, blurry vision, the sensation of something in the eye, discharge or swelling.  If you experience any of these, remove your lenses and consult an eye care professional immediately.  Initially, some cases have been diagnosed as the herpes simplex virus which requires different medications which will not be effective.  If you are receiving treatment and the symptoms persist, most notably an increase in pain, return to your doctor as soon as possible.  Diligence, early detection and treatment will increase the chances of successful treatment.

Prevent Blindness America and acanthamoeba keratitis research ► Prevent Blindness America and acanthamoeba keratitis research ▼

Dr. Charlotte Joslin, at the University of Illinois-Chicago has been actively researching the Acanthamoeba keratitis outbreak in Chicago.  She received her first Prevent Blindness America Investigator award in 2006 for her study, “Chicago-area Acanthamoeba Keratitis.”  In 2008, she received her second grant and will continue her research on the subject with the project “The Role of Domestic Water Supply in a Persistent Acanthamoeba Keratitis Outbreak Following a Contact Lens Solution Recall.”