Newer Contact Lenses Don't Cut Infections
Daily Disposables, Newer Materials Have Not Reduced Infection; Overnight Wear Increases Risk Most, Studies Show
Contact Lenses & Infection Risk: The U.K. Study continued...
''Gas-permeable lenses are safer than any other type of lenses,'' Dart says, although he adds that they are not a popular choice among contact lens wearers, who tend to find them uncomfortable.
Even though the daily disposable wearers had more risk of infection than those who wore reusable soft lenses, vision loss from the infection was less likely to occur in the daily disposable lens wearers. None of the daily disposable lens wearers lost vision beyond 20/40, he says.
"It's safer to use a daily disposable [than a reusable]," Dart says, "because the type of bugs you get are less nasty." Reusable lenses must be disinfected and stored, and "lens cases harbor nasty bacteria in some patients," he says.
Some brands were associated with more infections than others, Dart found, but he says most of the contact lenses he studied have probably been redesigned since the study was done.
Contact Lenses & Infection Risk: The Australian Study
In the second study, a team led by Fiona Stapleton, PhD, of the University of New South Wales, interviewed 285 contact lens wearers who had microbial keratitis and 1,798 lens wearers without the infection.
After looking at the type of lenses worn, wearing patterns, and other factors, they estimated the annual incidence for the infection.
They also found that new lens materials haven't reduced infection. Overnight use was the strongest risk factor for infection, just as in the U.K. study.
For instance, they estimate that microbial keratitis occurred in 1.2 per 10,000 of those who wore daily-wear rigid gas-permeable lenses but in 25.4 per 10,000 of those who wore silicone hydrogel lenses overnight.
Other factors that increased the risk of infection included smoking, buying lenses over the Internet, wearing lenses beyond the recommended time spans, and improper hand cleaning before handling lenses.