May 28, 2007
Outbreak of Eye Infections Puzzles Officials
By LAWRENCE K. ALTMAN
Health officials and eye doctors are puzzled by an outbreak of a rare but potentially blinding eye infection that led the manufacturer of a contact lens cleaning solution to withdraw one of its products this weekend.
The outbreak resembles one last year that was linked to a different manufacturer’s lens solution and a different microbe. In both instances, the cornea, the eye’s transparent outer covering, is at risk. But why two different microbes caused the outbreaks is not known.
“It is beyond comprehension,” said Dr. Dan B. Jones, the chairman of ophthalmology at Baylor College of Medicine in Houston, who detected a case of acanthamoeba keratitis, which is behind the current outbreak, on Friday.
Acanthamoeba keratitis is caused by a parasite, can be difficult to detect and is hard to treat. This outbreak has involved at least 138 patients.
Last year, an outbreak of fusarium keratitis was caused by a fungus; there were 164 confirmed cases. It was linked to ReNu With MoistureLoc made by Bausch & Lomb, but how the product caused the problem is unknown.
Epidemiologists from the Centers for Disease Control and Prevention have linked the acanthamoeba keratitis outbreak to AMO Complete Moisture Plus Multi-Purpose Solution. Advanced Medical Optics of Santa Ana, Calif., manufactures the solution, which is used to clean and store soft contact lenses.
AMO said there was no evidence to suggest that its product was contaminated with acanthamoeba and that it took its action as a precaution.
Federal officials have advised consumers to stop using the solution immediately and to discard all partly used or unopened bottles and switch to alternative products.
They have also advised people to throw out their current contact lenses and the lens storage cases because they may harbor the acanthamoeba parasite.
And, officials said, those who have used the product should call an eye doctor if they have experienced eye pain or redness, blurred vision, sensitivity to light, the feeling of something in the eye or excessive tearing.
The symptoms, which resemble those of other eye problems, can last weeks to months and vary among patients. The infection can lead to the need for a corneal transplant or removal of an eye.
Acanthamoeba are ubiquitous and can be found in water, soil and spouts and sinks in a home. But why they cause so few cases among the estimated 35 million soft lens users in this country is a mystery.
Investigations of the acanthamoeba outbreak are ongoing and being conducted by the disease control agency, the Food and Drug Administration, state and local health departments and eye doctors around the country.
Dr. Jones, the Houston expert who has participated in the investigations, said doctors and health officials needed to monitor better the occurrence of corneal infections among contact lens users. He said he did not know whether the current outbreak would have been detected if last year’s had not been identified.
Doctors also need to be more suspicious about the possibility of such infections because many cases have been initially attributed to the herpes simplex virus or other microbes, which respond to drugs that do not help patients with acanthamoeba, Dr. Jones said.
Another need, he said, is to find more effective ways to notify the public and patients quickly about the removal of a product from the market because of a health hazard. The solution was still on shelves in several chain drug stores in Manhattan and Houston on Sunday.
Dr. Jones said the two outbreaks indicated that environmental and other factors beyond contamination might be involved.
Acanthamoeba infections have been reported in many countries. Dr. Jones’s team is credited for first identifying a corneal infection from acanthamoeba in the United States, in a rancher who was injured in an accident in Texas in 1973. That case did not involve contact lenses: while the rancher was working in a field, a piece of wire and hay hit his eye.
He used irrigation water to wash it out and the eye became infected. A number of doctors whom the rancher consulted could not successfully treat it. With the aid of microbiologists at Baylor and the disease control agency in Atlanta, the team identified it as acanthamoeba.
In the mid-1980s, doctors reported an acanthamoeba outbreak among contact lens users in this country.
Recognition of the current outbreak has its origins in what seemed to be an increase in the number of cases found at the University of Illinois in Chicago over the last three years. The Illinois doctors reported the cluster to the disease control agency in March 2006.
The agency then asked a number of eye centers in the United States to determine if they had noted an increase in cases; the findings were inconclusive.
In January, the agency expanded its inquiry to 22 eye centers and found that 13 had an increase in cases since 2004. In mid-March, the agency said, it began a more extensive investigation.
Dr. Jones’s team, which was among the researchers at the eye centers, found 16 confirmed cases since 2005, excluding the one on Friday. In 2004, Dr. Jones’s department treated 12 such cases.
Scientists do not know how many acanthamoeba are needed to cause an infection or how much of a lens solution may be needed to cause damage.
Investigators are exploring a variety of possibilities in seeking the cause of the outbreak. Among them is whether something like a change in chlorination practice has led to an increase in the number of acanthamoeba in certain water supplies.
Investigators are also looking at the chemicals in the AMO solution, and whether the amoeba could bind more readily to newer generation silicone lenses, or whether something about certain kinds of contact lenses, or the length of their use, might increase the risk of infection among wearers.