Contact lenses that dispense prescription drugs

EYE DISEASES like glaucoma could one day be treated by pharmaceuticals delivered through contact lenses. Chemical engineers from the University of Florida say they've been able to make soft contact lenses containing tiny embedded particles that slowly release drugs directly where they're needed.

The research was presented at the 225th national meeting of the American Chemical Society, held in New Orleans.

"One of the biggest problems with using eye drops to deliver medication to the eyes is that about 95 per cent of the medication goes where it's not needed," said Anuj Chauhan, one of the authors of the study.

He said that eye drops applied topically mix with tears, which then drain into the nasal cavity and from there, get into the bloodstream and to other organs, where the drugs can cause serious side effects. For example, Timolol, used to treat glaucoma, causes heart problems. But drugs in a contact lens could be released slowly enough to stay in the eye.

Chauhan and his graduate student and coauthor, Derya Gulsen, have found a way to encapsulate a drug in nanoparticles — tiny particles much smaller than the eye can see — which can then be mixed into the contact lens matrix during manufacturing of the lens.

In theory, the disposable, drug-laden contact lenses could be worn for up to two weeks, steadily delivering a supply of the drug directly to the eye where it's needed. The same lenses could be used to correct vision while delivering medication.

Chauhan said the process could also be used to incorporate antibiotics into the matrix of a lens, making an extended-wear lens that would leave its wearer less vulnerable to bacterial infections — a chief drawback of such lenses today.

Researchers have got drugs into contact lenses, by soaking lenses in a drug solution or by trapping the drug in a hollow cavity between two pieces of lens material. "But contact lenses soaked in drug solutions are not effective at delivering medicines for a long period," Chauhan said.