External contamination could have been the cause of the recent U.S. outbreak of corneal infections related to the contact lens solution according to researchers on Tuesday.
When the Centers for Disease Control and Prevention received multiple reports of the corneal infection, Fusarium keratitis, the Bausch & Lomb solution Renu with MoistureLoc was recalled from the worldwide market in May.
The Canadian division of Bausch & Lomb has confirmed that this product was not sold in Canada.
The fungus Fusarium is usually found in soil and plants. The disease microbial keratitis is a rare and serious infection which can lead to permanent vision loss or require corneal transplantation treatment.
The annual incidence of microbial keratitis has been found to be four to 21 per 10,000 soft contact lens wearers, according to the Journal of the American Medical Association.
On June 1, 2005, Dr. Douglas C. Chang from the Centers for Disease Control and Prevention started a study on reviewing the link between the outbreak of Fusarium keratitis with contact lens products, hygiene practices and activities.
Chang's study examined 123 people of the 164 that had been afflicted with Fusarium keratitis.
According to the study published by the researchers in Aug. 23/30 issue of JAMA "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 did not find Fusarium in the factory that produced the solution, the warehouse or any unopened solution bottles.
Bausch & Lomb has claimed that they have conducted thousands of tests but found no evidence of tampering, contamination or counterfeiting.
According to the company an aspect of the MoistureLoc formula, in conjunction with external factors probably increased the risk of the Fusarium infection in rare instances.
The researchers cautioned doctors on the need for vigilance in diagnosing and treating fungal keratitis and urged consumers to discontinue the use of MoistureLoc.
In addition soft contact lens users were also advised to pay close attention to their hygiene practices, especially the washing and drying of hands before handling lenses and adding new lens solution into the storage case after each use.
Contact lens wearers have also been told to pay close attention to product directions for contact lenses and lens solutions.