A Prescription For The Future: A Contact Lens That Delivers Drugs

March 23, 2003

GAINESVILLE, Fla. — People suffering from glaucoma or other eye diseases could one day replace eye drops with drug-laden contact lenses that deliver medication precisely when and where it is needed.

University of Florida researchers have developed soft contact lenses that contain tiny drug-filled particles capable of releasing medications slowly and steadily into the eye. Such lenses would have significant advantages over eye drops, which convey only a small portion of their drugs to the eye while allowing the rest to enter the bloodstream and other tissues where they can cause harmful side effects, said Anuj Chauhan, a UF assistant professor of chemical engineering.

Chauhan and UF chemical engineering doctoral student Derya Gulsen will present their findings Sunday at the American Chemical Society’s national meeting in New Orleans.

“As soon as you apply eye drops, they quickly mix with tears and a significant portion drains into the nasal cavity and eventually gets absorbed into the blood stream,” Chauhan said. “There clearly is a need for drug-delivery systems that can solve this problem, and we believe our system provides one potential solution.”

Millions of Americans suffer from cataracts, glaucoma and other eye diseases. Although surgery is a possibility in some cases, these diseases often are treated with drops packed with powerful drugs. Some of this medication reaches its target, but the majority winds up in the body, Chauhan said. For the estimated 2 million Americans with glaucoma, a condition that causes increased pressure in the eye that can result in blindness, negative drug side effects range from impotence to heart problems, he said.

Chauhan and Gulsen developed a technique to encapsulate a test drug in tiny “nanoparticles” – each measuring 50 nanometers, or 50 billionths of a meter. They mixed these oil-based particles into the same material used to make commercial contact lenses, poly-2-hydroxyethyl methacrylate, and fashioned large prototype lenses with characteristics similar to manufactured ones.

The drug particles are so small they don’t scatter light, so they didn’t cloud the finished lenses, Chauhan said. And because the lenses would be suspended in the moist environment of the eye, the drug would in theory seep out slowly.

In Chauhan’s laboratory tests, a test drug, Lidocaine, a local anesthetic, diffused from the contact lenses into a surrounding solution in quantities appropriate for therapy for about five days. That sharply contrasted what happens with eye drops, where medication is delivered in a single rapid burst and disappears quickly.

The drug-laden nanoparticles not only provide slow release, they also distribute the drug into the thin area sandwiched between the eye and the contact lens. Chauhan predicted this would mean far less drug would escape into the tears, down through the nasal cavity and into the body, Chauhan said.

Ken Polse, a professor of vision science and optometry at the University of California-Berkeley’s School of Optometry, said the concept of delivering medication through contact lenses has been around since soft lenses were introduced in the 1970s.

However, the idea was abandoned due to technical problems that Chauhan’s technique appears likely to overcome, he said.

“His new approach provides a real chance at having a method to provide sustained and controlled drug delivery to the eye, which could have important clinical implications,” Polse said.

But Polse and Chauhan noted that many obstacles remain.

“The major challenges are the ability of the eye to wear the lens day and night for several days without damage to the eye, providing sustained and constant drug delivery, and cost,” he said.

Chauhan said in theory the lenses would be disposable, with patients changing them for new lenses every couple of weeks, as is done with disposable lenses currently. The drug-infused lenses are made of the same material as regular contact lenses, so he does not expect their cost to be prohibitive. The next step in his research, he said, is to learn more about how to vary the rate or timing of drug delivery, which could be done through changing the size or concentration of the nanoparticles.

After that, the contact lenses would have to be tested in animals and then people before they could reach the market, he said. The trials would seek to ensure, for example, that the oil drops that make up the particles are harmless to the eye. Chauhan, who has applied for a patent on the technique, estimated a commercial product is about a decade away.

Chauhan’s and Gulsen’s research has been partially funded by the Engineering Research Center for Particle Science and Technology.