WEDNESDAY, Aug. 21, 2002 (HealthDayNews) -- If you wear contacts, you know all about the endless need to take them out for cleaning.
Wouldn't it be great if you could safely leave your contacts in from, say, now until Thanksgiving?
If new research bears out, that may be possible one day.
A study with albino rabbits found that coating contact lenses in an element called selenium can keep dangerous bacteria from accumulating. After two months, the 12 rabbits who wore the contacts continuously had no ill eye effects and no bacterial infections. The findings were to be presented today at the American Chemical Society's annual meeting in Boston.
Ted Reid, lead author of the study, has been continuously wearing the selenium-coated contacts in his own eyes for a week.
"I had no problems," says Reid, a professor of ophthalmology and visual science at the Texas Tech University Health Sciences Center.
For the most part, the eyes are a hardy membrane, each day fending off all kinds of bacteria.
However, a contact lens lacks that ability, Reid explains. Instead, the lens can act as an incubator for bacteria, which attach to the glass and grow into a coating called a biofilm.
The most dangerous kind can cause blindness, he says: "Some biofilms can eat through a cornea in a day."
To prevent infection, most contact lenses need to be removed daily, or at least weekly, for cleaning and disinfection. Currently, the U.S. Food and Drug Administration (FDA) has approved two brands that can be left in for up to 30 days, Reid says.
Selenium is a naturally occurring element that is present in many of the foods we eat, including plants and meat, and also plays a role in the body's immune function, killing bacteria by triggering the formation of superoxide radicals by white blood cells.
The selenium coating is only one molecule thick and doesn't interfere with the ability of the lens to let in oxygen, Reid says. Nor is there any leaching of the selenium into the eye. Even if there was, it's such a miniscule amount it would do no harm, he adds.
In addition to the tests in rabbits, researchers also submerged selenium-coated contacts in a thick bacteria soup. After four days, the contacts remained free of bacteria.
The findings are interesting, says Dr. Richard Bensinger, a spokesman for the American Academy of Ophthalmology, but Reid's discovery doesn't deal with one of the primary reasons why contact lenses have to be removed.
Over time, contact lenses become coated in debris -- dirt from the environment, proteins dissolved in tears that dry on the lens and dead cells that are shed as part of the body's constant process of renewal.
"Lenses have to removed not only due to the risk of infection, but because crud accumulates on them that contributes to a loss of transparency or discomfort," says Bensinger, chairman of the eye department at Swedish Hospital Medical Center in Seattle.
Eye infections due to contact lenses are very rare, he adds. That's because the eye already has a brutally effective weapon in the fight against bacteria: tears.
"The bacterial issue is real, but infections are fairly uncommon because tears are inhibitory to that growth," Bensinger says.
"Reid's coating might be a little extra insurance policy, but it probably won't increase the longevity of the lenses beyond what they are already," he adds.
Reid believes not only will his coating extend the life of contacts, but also selenium could have other uses.
After cataract surgery, secondary cataracts can form around the new plastic lens that's inserted in the eye. Though preliminary, tests show coating a lens with selenium can interfere with the growth of new cataract cells, Reid says.
As for contact lenses, the next steps are more tests in humans and approval from the FDA. The approval process for a medical device is generally shorter than that for a drug, and Reid hopes selenium-coated contacts could be available to consumers within two years.
What To Do
To read more about the types of contact lenses currently on the market and how to care for them, check out the Contact Lens Manufacturer's Association or the Canadian Ophthalmological Society.
