Contact lenses could be the key to improving glaucoma treatment, according to new research.
A study by scientists at the University of Florida in Gainesville found that specially medicated contact lenses loaded with the dietary supplement vitamin E can keep glaucoma medicine near the eye, where it can treat the disease for almost 100 times longer than is possible with current commercial lenses.
At the moment, Pfizer"s Xalatan, whose unbranded name is latanoprost, is the most prescribed drug for the treatment of glaucoma.
Anuj Chauhan, who headed the research team, told the National Meeting of the American Chemical Society that this latest development in contact lenses could lead to more medication for glaucoma and perhaps other eye diseases.
Glaucoma is second only to cataracts as the leading cause of vision loss and blindness in the world, affecting almost 67 million people. Eye drops are the main treatment and work by relieving the abnormal build up of pressure inside the eye which occurs in people who suffer from the condition.
"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," Dr Chauhan said in a presentation at the conference.
"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 per cent of drugs in eye drops actually reach the cornea of the eye."
Dr Chauhan and his team have developed a new, extended-release delivery approach with the incorporation of the vitamin E. The clusters of vitamin E molecules form what they describe as "transport barriers", slowing down the movement of glaucoma medication from the lens into the eye.
As a result, the drug released from the lens stays in the tears much longer than the two to five-minute duration of eye drops. This means the treatment is much more effective.
"These vitamin structures are like "nano-bricks"," Dr Chauhan explained. "The drug molecules can"t go through the vitamin E. They must go around it."
"Because the nano-bricks 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," he added.
The research was conducted using laboratory animals and the lenses containing vitamin E nano-bricks administered medication for up to 100 times longer than most commercial lenses.
Dr Chauhan said that the contacts could be designed for continuous wear for up to a month and, in addition to treating glaucoma, could be an effective therapy for cataracts and dry eye.
Cataract problems are characterised by a clouding of the lens of the eye, while dry eye involves decreased production of tears. The latter affects around two in ten people and can lead to more severe problems.
Vitamin E is good for the eye in small amounts because it is a proven nutraceutical - a food product that provides medical benefits - and has anti-oxidant properties. Its presence in contact lenses blocks UV radiation, offering added protection from the sun.
"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," Dr Chauhan said.
by Adrian Galbreth