On May 29, 2007, Advanced Medical Optics said it still has no explanation for why its contact lens solution is causing an outbreak of Acanthamoeba, a rare eye infection in which amoebae invades the cornea of the eye.

In 2006, Bausch & Lomb’s contact lens care solution caused an outbreak of Fusarium keratitis, a different eye infection. Unlike last year’s infection, Acanthamoeba is much harder to treat when it penetrates the eye.

“The literature suggests that about half the patients will eventually need corneal transplants, compared to 30 percent for Fusarium,” said Dr. Robert Cykiert, an ophthalmologist at New York University Medical Center.

The overall risk of infection determined by doctors and health officials is extremely low, but they are encouraging contact lens wearers who have used Complete MoisturePlus to throw away any remaining solution, lens cases and lenses themselves.

Advanced Medical recalled Complete MoisturePlus solution after a CDC analysis found that users were seven times more likely to suffer infections.

Acanthamoeba is rare, but can be caused by failing to follow cleaning instructions and practices like sleeping with lenses in place. Officials say other factors, like how the chemicals in the solution interact with certain lenses, may contribute to the development of the infection.

Source: Barnaby J. Feder, “Lens fluid maker says link to infection unsolved,” New York Times, May 30, 2007.