Researchers have additional information concerning the recent outbreak of the corneal infection Fusarium keratitis, which was associated with use of a specific contact lens solution, according to a study in the August 23/30 issue of JAMA. After preliminary findings from this investigation were released in May, the product was withdrawn from the market worldwide.
Among the estimated 34 million contact lens wearers in the United States, microbial keratitis (corneal infection) is a rare but serious complication that may lead to permanent vision loss or the need for corneal transplantation. The annual incidence of microbial keratitis is estimated to be 4 to 21 per 10,000 soft contact lens wearers depending on overnight wear, according to background information in the article. Fusarium is a filamentous fungus commonly found in soil and plants and is the major cause of fungal keratitis in certain tropical or subtropical regions. Beginning in March, 2006, the Centers for Disease Control and Prevention received multiple reports of Fusarium keratitis among contact lens wearers in the U.S.
Douglas C. Chang, MD, of the Centers for Disease Control and Prevention (CDC) and colleagues conducted a study to determine the specific activities, contact lens hygiene practices, or products associated with this outbreak. Data for cases that occurred after June 1, 2005, were obtained by patient and ophthalmologist interviews for case patients and neighborhood-matched controls by trained personnel.
As of June 30, 2006, the researchers had identified 164 confirmed case patients with Fusarium keratitis in 33 states and 1 U.S. territory. Corneal transplantation was required or planned in 55 (34 percent). One hundred fifty-four (94 percent) of the confirmed case patients wore soft contact lenses. Forty-five case patients and 78 controls were included in the case-control study. In the final analysis, case patients were about 20 times more likely than controls to report using a specific contact lens solution, ReNu with MoistureLoc. The prevalence of reported use of ReNu MultiPlus solution was similar between case patients and controls. Fusarium was not recovered from the factory, warehouse, solution filtrate, or unopened solution bottles; production of implicated lots was not clustered in time.
Other products, including ReNu MultiPlus, private label Multiplus were not associated with Fusarium keratitis compared with nonusers of those solutions, the authors write.
Our findings, together with the results of environmental testing, suggest that exposure to Fusarium was likely the result of extrinsic contamination of contact lens solution bottles or lens cases occurring outside of the manufacturing or storage processes, perhaps in patients homes. However, suboptimal contact lens hygiene practices appear unlikely as the major explanation for the outbreak, the researchers write.
Ongoing studies may help to determine if the infections were caused by an interaction of its ingredients with Fusarium that might have permitted growth of the organism. In the meantime, clinicians should be vigilant in diagnosing and treating fungal keratitis, and users of MoistureLoc should discontinue the use of this product. Soft contact lens users should follow the instructions of their ophthalmologist or other eye-care professional and continue to pay careful attention to optimal hygiene practices, including washing and drying hands prior to handling lenses, storing lenses in new contact lens solution after each use, and carefully following directions for use of contact lens and contact lens solution products, the authors conclude.
Reference: JAMA. 2006;296:953-963.
Source: American Medical Association