Use of Complete MoisturePlus multipurpose solution (Advanced Medical Optics) has a strong association with a recent outbreak of Acanthamoeba keratitis (AK) cases in the Chicago area, but lens hygiene and changes to the water supply may also be responsible, according to a study in the American Journal of Ophthalmology.

A statistically significant increase in AK cases occurred in the Chicago area with 63 cases identified between June 2003 and the end of 2006. For this study, researchers from the University of Illinois at Chicago compared 38 AK patients (35 soft contact lens wearers) with 100 controls, surveying them about water exposure, contact lens hygiene (including solutions and lens types), and other habits of contact lens use in the six months prior to the onset of symptoms.

Results showed that soft contact lens wearers who had AK were significantly more likely to have exclusively used Complete MoisturePlus than the control group (55.2% vs. 10.5%).

Results of this study correlate to several in vitro studies in which Acanthamoeba proved largely resistant to contact lens solutions in general and Complete MoisturePlus in particular, the researchers say.

AMO initiated a global recall of its Complete MoisturePlus multipurpose solution on May 25, when the U.S. Centers for Disease Control and Prevention reported that 21 out of 46 patients who developed Acanthamoeba keratitis since January 2005 reported using Complete MoisturePlus products. The CDC said that patients who used Complete MoisturePlus had a seven times greater risk of developing AK than those who did not.

However, Complete MoisturePlus was not the only factor associated with AK in this study. Our results demonstrate that the use of AMO CompleteMoisturePlus Multi-Purpose Solution is strongly associated with AK diseasebut it was not a factor in nearly 40% of cases, says principal investigator Charlotte Joslin, O.D.

The researchers also found an association between three other contact lens use factors and infection. Among them:

Re-using solution. The AK patients were statistically more likely to report solution reuse or topping off six or more times per month vs. five or fewer times per month (58.6% vs. 25.6%).

Not rubbing lenses when cleaning them. The American Optometric Associations Cornea and Contact Lens Section advises patients to rub lenses for enhanced cleaning even when using a solution with No Rub labeling.

(Since its recall, AMO has announced plans to launch a new multipurpose solution under the Complete namebut with a Rub label. The company plans to begin promoting the new solution in the fall.)

Showering with lenses on. Showering can scatter water-borne microbes into a mist and increase exposure to the microbe that causes the infection, Dr. Joslin says.

The researchers recommend evaluating changes to the water supply as a possible cause of infection, especially because this is the second recent outbreak of an extremely rare eye infection.

Last year, Bausch & Lomb discontinued its ReNu with MoistureLoc multipurpose solution after it was linked with an outbreak of Fusarium keratitis.

Recent regulations from the Environmental Protection Agency have decreased the allowable levels of disinfection by-products in the water supply, Dr. Joslin says. This, in turn, may have increased the microbial load that contact lens solutions must kill to prevent disease.

Joslin CE, Tu EY, Shoff ME, et al. The association of contact lens solution use and Acanthamoeba keratitis. Am J Ophthalmol 2007 Jun 21; [Epub ahead of print].