TUESDAY, Aug. 22, 2006 (HealthDay News) -- Government researchers report that a recent outbreak of severe eye infections was indeed associated with the use of ReNu with MoistureLoc contact lens solution, but a chemical reaction that can occur with the solution appears to be the actual culprit.
Officials also believe the fungal contamination occurred in patients' homes, and not in the manufacturing or storage process.
"We think that there's something about the chemical make-up of the solution that allows the fungus to grow and cause infection," said study senior author Dr. Benjamin J. Park, medical officer with the U.S. Centers for Disease Control and Prevention. "We don't know the exact mechanism, but it's important that users of solution don't use Moistureloc."
After the same research team came out with a preliminary report in May, Bausch & Lomb recalled the solution.
For the 34 million contact lens wearers in the United States, the risk of developing keratitis, an infection that can lead to blindness or the need for a corneal transplant, is about four to 21 per 10,000. The risk is amplified for soft lens users, and by wearing lenses overnight or not following correct care protocols.
In February, however, unusually large clusters of patients with Fusarium were reported in Singapore and Hong Kong. A high proportion of these individuals had used a Bausch & Lomb ReNu brand contact lens solution.
Beginning in March of this year, CDC officials started receiving reports of similar cases among contact lens wearers in the United States.
In May, Bausch & Lomb stated that the combination of moisturizing agents exclusive to MoistureLoc could increase the risk of keratitis infections in unusual circumstances. HealthDay's attempts to reach the company for comment on this latest report were unsuccessful.
For this study, which appears in the August 23/30 issue of the Journal of the American Medical Association, CDC researchers looked at confirmed cases of Fusarium keratitis that occurred after June 1, 2005.
As of June 30, 2006, 164 cases had been identified in 33 states and one U.S. territory. About one-third (34 percent) of these patients required corneal transplantation. Almost all (94 percent) wore soft contact lenses.
This latest paper focused on 45 patients and 78 controls. Sixty-nine percent of patients had used ReNu with MoistureLoc, compared with 15 percent of controls.
Researchers did not find Fusarium at the factory or warehouse, or in unopened solution bottles.
Ongoing research is trying to determine the exact mechanism of infection, although when 39 isolates of the fungus were tested, at least 10 different genetic types were found. "This suggests that the organism had a lot of different sources," Park said.
In the meantime, contact lens wearers should take proper care of their eyewear.
"There seems to be an association of this infection with patients who don't replace their contact lens solution on a daily basis. That's a dangerous thing to do," said Dr. Robert Cykiert, a clinical associate professor of ophthalmology at New York University School of Medicine in New York City. "I ask my patients if, when they take a bath, do they drain the bathtub at the end or jump into the same bathwater the same day. You're putting your contacts in old bathwater."
"People who are reusing the old solution are more likely to get an infection," Park confirmed. "But we don't think that this outbreak is due to hygiene measures alone. The most important component was clearly the solution."
For more on Fusarium keratitis, head to the American Academy of Ophthalmology.