It was outbreaks in Asia and the United States of cases of the fungal infection, called Fusarium keratitis, that sparked the May 15 market recall of Bausch & Lomb's lens solution ReNu with MoistureLoc.
A detailed report of the Singapore cases -- which stretch from March 2005 through May of this year -- appears in the June 28 Journal of the American Medical Association.
That study also revealed that Bausch & Lomb, in a letter last month, had pretty much pinpointed what in the solution could be causing the Fusarium keratitis.
According to Bausch & Lomb, the combination of moisturizing agents exclusive to MoistureLoc could increase the risk of Fusarium infections in unusual circumstances. In a letter to the American Academy of Opthalmology in May, company vice president Angela Panzarella said, "While our investigation has confirmed that alexidine is a safe and effective disinfecting agent, the data suggest that under certain extreme conditions the concentration of polymers included in the formula to enhance comfort may make the solution more likely to be contaminated with Fusarium in the environment."
Fusarium keratitis is usually a rare infection, but cases in Singapore have increased sharply since March 2005, according to doctors who wrote the new report. Recently, 122 cases have been reported in the United States and 33 in Hong Kong, suggesting that there may be a worldwide outbreak of the infection among contact lens wearers.
In their study, a team led by Dr. Wei-Boon Khor of the Singapore Eye Research Institute looked at all cases of fungal keratitis among contact lens wearers from March 2005 through May 2006. The researchers took biopsy samples of the patients' corneas as well as contact lenses, lens cases and contact lens solutions. They also interviewed patients by phone.
The researchers found that during the 15-month period, 66 contact lens wearers (68 affected eyes) were diagnosed with Fusarium keratitis -- a big jump from the one or two cases per year that doctors there usually see.
Using this data, the researchers estimated the annual incidence of Fusarium keratitis in Singapore rose to 2.35 cases for every 10,000 contact lens wearers.
Among the patients, 98.5 percent wore soft, disposable contact lenses, and close to 94 percent said they used ReNu brand cleaning solution. This included 42 patients (63.6 percent) who used ReNu with MoistureLoc. Six patients said they used another Bausch & Lomb brand, Renu MultiPlus, while 11 said they used some type of (unspecified) ReNu multipurpose cleaning solution.
Forty-four of the Singapore patients suffered sight-threatening lesions severe enough for them to be hospitalized for an average of 6.5 days. In addition, five patients had to undergo corneal transplantation.
Outbreaks like these have led Bausch & Lomb to investigate the link between the lens solution and fungal keratitis. In her letter, Panzarella said the polymers included in ReNu with MoistureLoc could boost the risk for Fusarium contamination, especially when users don't take recommended precautions.
"This may occur under conditions, for example, where the solution is allowed to evaporate, the solution is not regularly replaced in the lens case, or when the case is not cleaned properly. This may lead to the contact lens becoming contaminated with Fusarium and could create an environment for potential infection," Panzarella said .
Bausch & Lomb spokeswoman Meg Graham told HealthDay that no other reasons for the outbreaks have been found.
The Singapore team agreed that poor contact lens care may have played a role in the infections.
Close to 82 percent of the patients had poor lens hygiene habits, they said, including wearing daily contacts overnight, wearing expired lenses and wearing contacts while swimming. However, these habits do not fully explain the outbreak, Khor's group stressed.
The researchers note that seven U.S. patients who developed the infection had also used products from Advanced Medical Optics or Alcon, and some of them had used several products.
One manufacturer noted that its products were not involved in the current outbreak. "Advanced Medical Optics (AMO) has never had a confirmed case of fungal keratitis attributed to any of its products," said spokesman Steve Chesterman. "AMO conducts a full battery of pre-clinical testing in the development of its contact lens care products to ensure that they meet all applicable U.S. and international standards for antimicrobial effectiveness, preservative effectiveness, and sterility," he added.
Calls to Alcon for comment were not returned.
"By highlighting this series of Fusarium keratitis among contact lens wearers in Singapore, we hope to alert physicians and other eye care clinicians worldwide to maintain a high index of suspicion for fungal infection when evaluating and treating patients with contact lens-associated microbial keratitis," the researchers concluded.
One expert thinks the MoistureLoc solution is only part of the problem.
Dr. Robert Cykiert, a clinical associate professor of ophthalmology at New York University School of Medicine, said proper contact lens hygiene is key to keeping eyes safe.
This increase in Fusarium keratitis infections is due to Bausch & Lomb's ReNu with MoistureLoc and to poor contact lens hygiene among patients, Cykiert said. "There have always been problems with patients not caring for their contact lenses. So, you have an underlying low percentage of infection," he said.
"They don't properly care for their contact lenses, they don't wash their hands properly, they don't replace solution daily, and they sometimes sleep with their lenses, which increases the risk of getting an infection," Cykiert said.
The MoistureLoc solution adds to the problem, because it creates a film on contact lenses and on contact lens cases, Cykiert said. "This film puts a protective coating over the fungus, so it allows the Fusarium to adhere to the contact lens and to the contact lens case," he said.
"If you have poor hygiene, poor handling, poor disinfecting techniques, and you combine it with a solution like that, you suddenly get a huge number of infections," Cykiert said.
Cykiert cautions patients not to use Bausch & Lomb's ReNu with MoistureLoc solution. "The problem is that there are still some people out there who have that solution at home and haven't discarded it," he said. "Not using it dramatically reduces the chances of getting the infection," he added.
To reduce further the chance of getting an infection, Cykiert recommends that people wash their hands before handling their contact lenses and replace their contact lens solution every day.
More information
For more on fungal keratitis, head to the American Academy of Ophthalmology.
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