Glaucoma is second only to cataracts as the leading cause of vision loss and blindness in the world. It affects almost 67 million people. Eye drops that relieve the abnormal build-up of pressure inside the eye that occurs in glaucoma, are a mainstay treatment.
"The problem is within about two to five minutes of putting drops in the eye, tears carry the drug away and it doesn't reach the targeted tissue," said Anuj Chauhan, a chemical engineer at the University of Florida . "Much of the medicine gets absorbed into the bloodstream, which carries it throughout the body where it could cause side effects. Only about one to five percent of drugs in eye drops actually reach the cornea of the eye."
Chauhan and colleagues have developed a new extended-release delivery approach incorporating vitamin E into contact lenses. The invisible clusters, or aggregates, of vitamin E molecules form what Chauhan describes as "transport barriers." that slow down the elusion of the glaucoma medication from the lens into the eye. The drug released from the lens into the eye stays in the tears far longer than the 2-5 minutes with eye drops, leading to more effective therapy.
"These vitamin structures are like 'nano-bricks'," Chauhan said. "The drug molecules can't go through the vitamin E. They must go around it. Because the nanobricks are so much bigger than the drug molecules – we believe about a few hundred times bigger – the molecules get diverted and must travel a longer path. This increases the duration of the drug release from the lenses."
Clinical trials of the new lenses are expected to begin within a year to 2 years.
In research with laboratory animals, the lenses containing vitamin E nanobricks administered drugs up to 100 times longer than most commercial lenses. The lenses could be designed for continuous wear for up to a month, Chauhan said. In addition to treating glaucoma, the contacts could help other eye conditions, such as cataract and dry eye. Cataract is a clouding of the lens of the eye, and dry eye involves decreased production of tears. It affects about 2 in 10 people and can lead to more severe eye problems.
"Vitamin E is a proven nutraceutical that in small amounts is good for the eye because of its ant-oxidant properties. Also Vitamin E presence in the contact lenses blocks UV radiation, leading to increased protection against the UV light. Our research has shown that the vitamin can be loaded into the lenses without any reduction in transparency. We believe it could be helpful in disease treatment and in prevention as well," he said.
Citation: Cheng-Chun Peng, Jinah Kim, Anuj Chauhan, 'Extended delivery of ophthalmic drugs by contact lenses containing nanobarriers of vitamin E', ACS National Meeting, March 2010
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