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Contact Lenses Employed for Drug Delivery

Originally Published MDDI January 2005 R&D DIGEST   Maria Fontanazza

Originally Published MDDI January 2005

R&D DIGEST

Maria Fontanazza

Open wide: Nanometer-sized channels in a drug-laden contact lens may result in better delivery techniques and less waste.
(click to enlarge)

Using contact lenses as a method of drug delivery could provide an easier way to treat eye ailments ranging from dryness to glaucoma. At the Institute of Bioengineering and Nanotechnology (IBN) in Singapore, scientists have developed a technique that may be a useful alternative to eye drops. "Drug delivery using contact lenses provides a safer, painless, and more efficient alternative for ophthalmic drug delivery," says Edwin Chow, PhD, a research scientist at the institute.

Patients are often prescribed drops to treat an eye problem. However, Chow explains, "Dosage of medication through [the eye-drop] method is inconsistent and difficult to regulate, as most of the drugs are released in an initial burst of concentration." He also explains that a significant portion of the drug isn't absorbed, which contributes to further waste. By contrast, "Ophthalmic drugs delivered using a hydrophilic soft contact lens and a collagen shield soaked in a drug solution have been found to penetrate the eye in higher concentrations than when delivered via eye drops or subconjunctival injection," Chow says.

By using different materials and medications in the lens mixture, the technology has the flexibility to be refined and used for various treatments, such as vision correction, dry eyes, corneal wounds, and glaucoma.

Scientists at IBN have combined water, oil-based monomers, and a polymerized surfactant. These ingredients bond together and become a clear mixture. After an exact drug dose is added, the mixture is poured into a lens mold to harden. The resulting lens is laden with nanometer-sized channels, which allow the drug to flow onto the eye surface. This is an improvement made on past design attempts, which failed to achieve controlled drug release and resulted in high drug waste.

"Aside from providing an efficient method to deliver drugs consistently over an extended period, we also wanted to produce disposable lenses that could be worn for several days without damaging the eye," says Chow. By changing the lens mixture's structure, scientists can further control the drug flow, drug-delivery time, and channel width.

Similar research began at the University of Florida (Gainesville, FL) more than three years ago, where a group also developed drug-laden contact lenses. They began the research to address the potential for reducing certain side effects. The team was concerned because, when using eye drops, a portion of the drug eventually enters the bloodstream.

Anuj Chauhan, assistant professor of chemical engineering at the university, says that the contact lenses may diminish this unwanted effect. In addition, the benefits of the contact lenses include limiting drug waste, higher patient compliance, and slow and extended drug delivery that may increase the efficacy of the drugs.

Copyright ©2005 Medical Device & Diagnostic Industry

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