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Sept 21, 2012 by MARCO TORRES
People Who Wear Contact Lenses May Be At Risk of Going Blind Due To This Parasite

Millions of contact lens users are at risk of contracting a disease caused by a parasite that feeds on bacteria found on contact lenses. It nibbles through the eyeballs causing permanent visual impairment or blindness, scientists have warned.

Many people underestimate the risks of contact lenses, continuing to wear them when their eyes become tired or irritated and not cleaning them as directed.

Such practices increase the risk of permanent damage to the cornea, the transparent outer layer of the eye, including a loss of corneal cells, a thinning of the cornea and a change in the cornea's shape, referred to as warpage.

"Contact lenses have more of an effect on the cornea than most people realize," said Dr. Thomas J. Liesegang, an ophthalmologist at the Mayo Clinic in Jacksonville, Florida. He published a review of the literature on the topic in an issue of The CLAO Journal, a publication of the Contact Lens Association of Ophthalmologists. "In some cases, the effects can be reversible and in some they can be permanent."

An outbreak of Acanthamoeba keratitis (AK), a rare, potentially blinding, corneal infection has been increasing since 2004. Acanthamoeba is a genus of amoebae, one of the most common protozoa in soil, and also frequently found in fresh water and other habitats. The parasite is also found in dust, sea, showers and swimming pools.

The actual number of infections is small but treatment is long, painful and not completely effective.

In the United States, an estimated 85% of cases of this infection occur in contact lens users.

"It is a potential problem for every single contact lens wearer," the Daily Mail quoted Fiona Henriquez, of the University of the West of Scotland, as saying.

When the lens is put in the eye, it starts to eat its way through the cornea, which is the outer layer of the eyeball and breeding as it goes.

Symptoms include itchy and watery eyes, blurred vision, sensitivity to light, swelling of the upper eyelid and extreme pain.

According to Graeme Stevenson, an optician, vision can be permanently damaged within a week.

"Generally it leaves you with scarring. Your cornea is your window on life and if the infection penetrates in towards the third layer you are left with scarring, with a kind of frosty windscreen," Stevenson said.

In 2007, the CDC has received reports of 138 cases of culture-confirmed AK in 35 states and Puerto Rico, with complete patient data available for 46 case-patients. Thirty-nine of the 46 case-patients wore soft contact lenses.

Preliminary information obtained by CDC from patient interviews indicates that, among soft contact lens users who reported the use of any type of solution, 21 (58%) reported having used Advanced Medical Optics (AMO) CompleteR MoisturePlus Multi-Purpose Solution in the month prior to symptom onset. Out of the 37 case-patients for whom clinical data was available, 9 (24%) failed medical therapy and required or are expected to undergo corneal transplantation.

Some researchers have suggested that municipal water treatment type may play a role in the development of AK. Acanthamoeba organisms are present in the water of many households. A temporal association was noted between an increase in AK cases in the Chicago area and the implementation of the Environmental Protection Agency Disinfectants and Disinfection Byproducts Rule, which was aimed at decreasing potentially harmful disinfection byproducts in water.

Advice for avoiding the bug includes keeping lenses and cases clean and replacing them regularly. Other suggestions include:

- Discard current lens storage containers every 3-6 months.
- Discard soft lenses as recommended by manufacturer
- See a health care provider if experiencing any signs of eye infection: Eye pain, eye redness, blurred vision, sensitivity to light, sensation of something in the eye, or excessive tearing.
- All contact lens users should closely follow prevention measures to help prevent eye infections.
- Wear and replace contact lenses according to the schedule prescribed by an eye care professional.
- Remove contact lenses before any activity involving contact with water, including showering, using a hot tub, or swimming.
- Wash hands with soap and water and dry before handling contact lenses.
- Clean contact lenses according to the manufacturer's guidelines and instructions from an eye care professional.
- Use fresh cleaning or disinfecting solution each time lenses are cleaned and stored. Never reuse or top off old solution.
- Never use saline solution and rewetting drops to disinfect lenses. Neither solution is an effective or approved disinfectant.

The findings highlight the importance of promoting healthy habits among contact lens users, particularly discouraging the practice of topping off solutions and reinforcing safe hygienic practices among new users of contact lenses, as well as the need for standardized anti-Acanthamoeba testing of contact lens solutions.


Marco Torres is a research specialist, writer and consumer advocate for healthy lifestyles. He holds degrees in Public Health and Environmental Science and is a professional speaker on topics such as disease prevention, environmental toxins and health policy.

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