Contact Lenses Used to Deliver Eye Drugs

Originally Published MDDI May 2003

R&D DIGEST

In addition to correcting vision, contact lenses could one day deliver controlled doses of medication, eliminating the need for eye drops. Researchers at the University of Florida, who are working on the new technology, believe the novel drug-delivery method could provide a number of benefits to contact lens wearers. 

According to the researchers, drugs delivered as drops using conventional methods can drain into the nasal cavity and then into the bloodstream and other tissues. This can result in serious side effects, such as heart problems. Because of the process in which the drops are given, there may initially be an overdose of sorts, declining to levels too low to have an effect. 

Drugs delivered via a contact lens, however, could be released slowly enough to stay in the eye, the researchers say. According to Anuj Chauhan, PhD, the project's leader, there are four main advantages to the new drug-delivery method. In addition to reduced side effects, the technique promotes increased compliance, reduced drug consumption, and delivery of a continuous dose rather than a sudden bolus. The method can also be used to deliver antibiotics, which could give lens wearers protection against bacterial infections. 

The delivery mechanism entails encapsulating drugs in nanoparticles that are then mixed into the contact lens matrix during manufacture. Says Chauhan, “We control particle size and hydrogel morphology to ensure homogeneity, which minimizes scattering, and hence ensures transparency.” The researchers say the lenses can be worn for up to two weeks, while delivering measured drug doses to the eyes. 

Previous efforts to develop a method for delivering drugs via contact lenses focused on soaking them in a drug solution or trapping the drug in a hollow cavity between two pieces of lens material. But the researchers say tests have shown that those methods may only work for a short period.

The group explains that when the nonparticle-filled lenses are placed on the eye, the drug diffuses from the particles through the lens matrix. It then passes into the thin film present between the cornea and the lens. The drugs remain in the film longer than drugs delivered via drops, which only remain there for about two minutes. 

Says Chauhan, “One of the biggest problems with using eye drops to deliver medication to the eyes is that about 95% of the medication goes where it's not needed. 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.” Chauhan speculates that the system could be developed commercially within about seven years.

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