ATLANTA (AP) _ Government officials are warning people to throw away a contact lens solution after an investigation linked it to a rare eye infection.
The warning concerns AMO Complete Moisture Plus Multi-Purpose Solution, used for cleaning and storing soft contact lenses, said a spokeswoman for the U.S. Centers for Disease Control and Prevention.
The solution seems to be a factor cases of Acanthamoeba keratitis, a painful eye infection that can lead to permanent vision loss or blindness.
The CDC and the U.S. Food and Drug Administration are investigating 138 confirmed cases.
The solution is made by Advanced Medical Optics Inc., a publicly traded company based in Santa Ana, Calif. A message left with a company spokesman was not immediately returned.
CDC officials said people should discard the solution, throw out their current contact lenses and toss the lens storage case. All of them may harbor the infecting amoeba, said Michael Beach, team leader in the CDC's division of parasitic diseases.
An estimated 85 percent of U.S. cases of Acanthamoeba keratitis occur in contact lens users, but it's extremely unusual _ the estimated prevalence is one to two cases per 1 million contact lens wearers. Contact lens wearers who practice proper lens care and people who don't wear contact lenses can still develop the infection.
It's hard to diagnose and treat _ and some of the drugs used to fight the infection are available only overseas or from compounding pharmacies.
The government's investigation began in 2004, when a University of Illinois-Chicago ophthalmologist _ Dr. Elmer Tu _ noticed more than a dozen cases of the infection. Normally, he might see only one or two in a year, Tu said.
UIC doctors saw 35 patients with the condition from May 2003 through September 2006. About 55 percent used the Advanced Medical Optics product exclusively, Tu said.
UIC investigators think the infection is not originating in the manufacturing process, but that the cleaning solution is not protecting people from the infection, which they get in their eyes through showering or swimming, Tu said.
The amoeba that causes the infection is naturally present in soil and water. Wearing contact lenses while swimming or in the hot tub appears to increase the risk of infection.
The cases were reported to the Illinois state health department, which notified the CDC. A CDC investigation in about 35 states led to Friday's announcement.
The solution is not marketed to protect against the amoeba. But ``it's supposed to be free of any type of microorganisms. It's not supposed to result in anyone getting an infection,'' said Julie Zawisza, an FDA spokeswoman.
The FDA will take information from the CDC investigation and try to discern what about the solution _ or how people were using it _ could be responsible for the infection cases, she added.
Health officials have interviewed 46 of the patients so far. Of those 36 wear soft contact lenses, and 21 use the Advanced Medical Optics solution, Beach said. It was a strong enough association to cause health officials to issue Friday's warning, Beach said.
Dozens of cases of this rare condition can be significant, eye experts said.
``It's a large number if it's happening to you. It's a large number if there is a little pocket of it. It's not a large number if you consider there are 35 million contact lens wearers in the United States,'' said Dr. William Ehlers, a University of Connecticut Health Center ophthalmologist.
The investigation is the second into eye infections associated with contact lens solution undertaken by the CDC and FDA in the past year. In 2006, a Bausch & Lomb multipurpose contact lens solution was linked to a fungal eye infection called Fusarium.
This week, Advanced Medical Optics disclosed it was considering making a bid to buy Bausch & Lomb, its eye-care products rival.