Advanced Medical Optics of Santa Ana, California yesterday triggered a voluntary recall of its product after an investigation by the CDC linked the product to an infection known as Acanthamoeba keratitis - inflammation of the cornea. If left untreated, the infection has the potential to cause blindness.
The Centre for Disease Control has identified and confirmed 138 cases of keratitis, a condition usually affecting healthy people who wear contact lenses - since January of 2005. Of the 46 confirmed patients interviewed by epidemiologists, 39 patients - or 85 per cent - wore soft contact lenses. Three individuals wore hard contacts, and four did not use either.
Investigators still do not know how the contamination occurred, and that any link to AMO Complete MoisturePlus Multi-Purpose Solution is preliminary. Officials with the CDC did state, however, that the risk of developing keratitis was at least 7 times greater in those individuals using the AMO product, than those who did not.
A statement by Advanced Medical Optics stressed that the voluntary recall is only a precaution and there is no evidence to suggest product contamination. The recall does not affect other AMO products.
While the infection is not spread person-to-person, it is nonetheless difficult to diagnose and treat. Symptoms include eye pain or redness, blurred vision, sensitivity to light, or a feeling that a foreign object is present in the eye. Symptoms can last anywhere from a few weeks to several months and differ among patients.
Acanthamoeba is a naturally occurring water-borne organism commonly found in water supplies, soil, sewage, and ventilation systems, among others.
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If left untreated, keratitis could lead to a corneal transplant, or even removal of an eye.
There are an estimated 30 million users of soft contact lenses in the United States. Meantime, the makers of AMO Complete MoisturePlus Multi-Purpose Solution are continuing to work with the Centre for Disease Control, and the U.S. Food and Drug Administration, to further monitor the issue.