Results of an ongoing investigation confirm a “strong association” between use of a particular type of contact lens solution - Advanced Medical Optics (AMO) Complete MoisturePlus Multi-Purpose Solution - and increased risk of a rare but serious eye infection called Acanthamoeba keratitis (AK).

Earlier this year, the company voluntarily recalled this product and called on consumers to stop using it after data showed a higher risk of eye infections.

AK is a painful infection of the cornea that can cause corneal scarring and sometimes blindness. Doctors at the University of Illinois at Chicago Cornea Service noticed a sharp increase in the number of AK cases in contact lens wearers beginning in 2003, with a total of 63 cases identified through the end of 2006. This compares to the “two or three cases a year we would normally expect to see,” Dr. Charlotte Joslin noted in a university statement.

They investigated 30 AK cases, comparing them with 39 matched “controls” who wore soft contact lens without developing the infection. Joslin and colleagues found that those with AK infection were significantly more likely to report having exclusively used AMO Complete MoisturePlus Multi-Purpose Solution than those without AK infection (55.2 percent versus 10.5 percent).

Users of this particular contact lens solution had a greater than 16-fold higher risk of developing AK.

However, the researchers note in the American Journal of Ophthalmology that nearly 39 percent of AK cases reported no use of AMO Complete MoisturePlus Multi-Purpose Solution or used it in combination with other solutions, suggesting that this is not the only risk factor for infection.

The current investigation provides some evidence that re-using contact lens solution, rubbing lenses during cleaning, and showering with lenses on increase the risk of eye infections in contact lens users.

SOURCE: American Journal of Ophthalmology, July 2007.