November 10 (HealthDay News) -- Prolonged exposure to high temperatures degrades the antifungal properties of the ReNu with MoistureLoc contact lens solution, which was implicated in a U.S. eye infection outbreak between 2004 and 2006, a new study says.

ReNu with MoistureLoc contains a microbial agent not found in other contact lens solutions. Between August 2004 and March 2006, there were 154 confirmed cases of the eye infection Fusarium keratitis among users of ReNu with MoistureLoc, made by Bausch & Lomb, the study authors said.

The U.S. Food and Drug Administration cited the company for inadequate temperature control in the production, storage and transport of ReNu with MoistureLoc produced at Bausch & Lomb's Greenville, S.C., plant.

In the new study, Dr. John D. Bullock, of the Wright State University Boonshoft School of Medicine in Dayton, Ohio, and colleagues conducted tests on ReNu with MoistureLoc and five other contact lens solutions.

"Two bottles of each solution were separately stored at room temperature and 60 degrees Celsius (140 degrees Fahrenheit) for four weeks, serially diluted and then tested for their ability to inhibit growth of 11 Fusariam isolates [seven of which were associated with the keratitis epidemic]," the researchers wrote.

Compared to the other solutions, ReNu with MoistureLoc showed the greatest decline in antifungal activity when stored at 60 degrees C. Clear Care and ReNu MultiPlus performed the best, the researchers said.

When the researchers focused on the strains of Fusariam associated with the keratitis outbreak, ReNu with MoistureLoc allowed fungal growth in 27 of 84 combinations when stored at room temperature and in 67 of 84 combinations when stored at 60 degrees C.

The study was published in the November issue of the Archives of Ophthalmology.

"The precise temperature, duration of exposure to elevated temperature and extent of temperature fluctuation that may diminish the antimicrobial activity of a particular contact lens solution is not known, and thus, additional studies may be warranted. However, our findings, coupled with the FDA reports of Bausch & Lomb's failure to regulate the storage and transport temperatures of the products manufactured in their Greensville plant, may be significant," the study authors concluded.

"Knowledge of the potential loss of antimicrobial activity of contact lens solutions and other pharmaceutical products when exposed to higher temperatures and the risk of such exposure when storing and transporting those products may help prevent such epidemics in the future," the researchers added.

SOURCE: JAMA/Archives journals, news release, Nov. 10, 2008