Contact Lenses That Dispense Prescription Drugs

The research was presented today at the 225th national meeting of the American Chemical Society, the world's largest scientific society, held this week in New Orleans.

"One of the biggest problems with using eye drops to deliver medication to the eyes is that about 95 percent of the medication goes where it's not needed," said Anuj Chauhan, Ph.D., 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, can cause heart problems. But drugs contained 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. Rather than being exposed to a sudden high dose of medication — from an eye drop, for example — the patient gets the right amount of medicine all the time.

The same lenses could be used to correct vision while delivering medication. And for a person whose vision doesn't need to be corrected, the lenses could be made without correction.

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.

Other researchers have tried getting drugs into contact lenses, either by soaking the lenses in a drug solution or trapping the drug in a hollow cavity between two pieces of lens material. "But contact lenses soaked in drug solutions are not very effective at delivering medications for extended periods of time," Chauhan said. "Our approach allows us great flexibility in designing controlled drug delivery vehicles that can be tailored to different drugs, but are also effective for extended periods of time."

The lenses are in the very early engineering design stages and have not been tested clinically. "We're in the very preliminary stages of developing this technology right now," Chauhan says. No in vitro or animal testing has yet been done.