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New antibacterial coating may prolong contact lens life

22.08.2002


The hassle of removing and cleaning your contacts every night, or even every month, could become a thing of the past, based on a study involving a new contact lens coating that kills bacteria.



The study involved rabbits. The coating: an extremely thin layer of selenium, a naturally occurring element found in soil, some plants and many foods we eat.

The rabbits showed no ill effects after two consecutive months of wearing the coated lenses, according to Ted Reid, Ph.D., of Texas Tech University Health Sciences Center in Lubbock, Texas, who presented the findings at the 224th national meeting of the American Chemical Society, the world’s largest scientific society.


Selenium, which is essential to our diet and immune system, kills bacteria by forming something called superoxide radicals. "It’s a natural mechanism we use in our body to kill bacteria," Reid emphasized. "That’s why we’ve had these contact lenses on rabbit eyes for two months and seen no affect whatsoever on the eye."

"I’m ready to put them in my eyes right now," Reid declared.

Nearly all extended wear contact lenses require the wearer to remove them at least weekly for cleaning and disinfection. The U.S. Food and Drug Administration (FDA) so far has approved only two brands that can be left in for up to 30 days. The selenium coating would let people keep their contacts in for at least two months, according to Reid.

The selenium coating is only one molecule thick and does not interfere with the ability of the contact lens to let in oxygen, or its prescription, Reid said. Nor is there any leaching of the selenium, he added. Even if it did, it’s not a problem, according to Reid.

"Let’s suppose all the selenium came off. The amount of selenium that’s on this device is probably .01 percent of what you had for lunch. We’re talking miniscule amounts."

Coating the lens is simple, Reid noted. "You just dip the contact lens into the solution, let it set for a few minutes, and it’s attached." So far, his lab has found the coating can stay attached for at least two years.

It might only be a couple of years until selenium-coated contacts are available to consumers, Reid said. More testing needs to be done before the FDA would grant approval for them, he added.

Coatings for contacts are only the tip of the iceberg, Reid pointed out. His research group is investigating several other possible applications for selenium coatings, including prevention of secondary cataracts and inactivation of the AIDS virus.

After cataract surgery, secondary cataracts can form around the new plastic lens that’s inserted in the eye, Reid explained. "Having the selenium on the surface of the lens, the new lens, interferes with the growth factors that promote the growth of those [secondary cataract] cells."

Although very preliminary, attaching selenium to antibody peptides shows potential for AIDS treatment, according to Reid. "We’ve tested it on the AIDS virus and shown that it will inactivate the AIDS virus in culture. We’re also sending some of this back to NIH [National Institutes of Health] and they’re going to be testing it for us." He did not speculate when those test results would be available.


The paper on this research, PMSE 229, will be presented at 2:00 p.m., Wednesday, Aug. 21, at the Westin Copley Place, Essex Northeast, during the symposium, "Synthetic Polymers in Ophthalmology."

Ted Reid, Ph.D., is a professor at Texas Tech University Health Sciences Center, Department of Ophthalmology and Visual Science, in Lubbock, Texas. He also is the vice chairman of the department and its director of ocular cell biology and is the chief science officer of Selenium Technologies Incorporated in Lubbock, Texas.

— Marvin Coyner

Charmayne Marsh | EurekAlert!
Further information:
http://www.acs.org/portal/Chemistry

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