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 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.
Contact Lenses & Infection: Study Interpretations
Finding that the newer lens materials don't reduce infection risk is
disappointing, Dart writes.
Although experts thought that the lack of oxygen getting to the cornea was a
factor in infections, the findings suggest that other factors may be more
important, he says.
The lenses may reduce the turnover of skin cells on the front of the eye,
for instance, Dart says, boosting infection risk.
The studies were funded from a variety of sources, including CIBA Vision
USA, which makes a variety of contact lenses. One of the supporting
organizations, The Vision Cooperative Research Center, receives a royalty on
the sale of silicone hydrogel lenses.
Contact Lenses & Infection: Second Opinion
The findings about the risk of overnight wear come as no surprise to Thomas
Steinemann, MD, a spokesman for the American Academy of Ophthalmology and
professor of ophthalmology at Case Western Reserve University
"That confirms what we have always known for years," he says.
"Sleeping in your lenses is not a good thing, even if they are continuous
wear. It is a risk factor, probably the risk factor, for microbial
keratitis-associated vision loss."
"Don't sleep in your contact lenses, ever," he says. "That
includes taking naps in them."
Also important, he says, is to pay attention to lens hygiene. "Follow
your eye care professional's and manufacturer's advice about cleaning," he