Sustained-Release Contact Lens Could Help Treat Glaucoma

Researchers at Children's Hospital Boston (CHB; MA, USA), the Massachusetts Eye and Ear Infirmary (Boston, MA, USA), and the Massachusetts Institute of Technology (MIT; Boston, USA) created a two-layer contact lens that is comprised of an inner drug-bearing biodegradable polymer film made of polylactic-co-glycolic acid (PLGA), and an outer coating made out of Poly(2-hydroxyethyl methacrylate) (pHEMA), a polymer that forms a hydrogel in water. In laboratory testing, the prototype lenses dispensed ciprofloxacin--an antibiotic often used in eye drops--for 30 days; in other tests, the lenses continued releasing the drug for up to 100 days. The amounts dispensed were sufficient to kill pathogens in a laboratory assay. Possible applications include treatment of conditions such as glaucoma and dry-eye, which require frequent daily eye drops. The study describing the new lens was published in the July 2009 issue of Investigative Ophthalmology and Visual Science.

"Patients taking eye drops multiple times daily may absorb as little as 1 to 7 percent of the intended dose into the eye due to blinking and tearing. This prototype of a contact lens allows the delivery of large or at least therapeutically relevant quantities of drug for extended periods of time, meaning at least a month, with what's called zero-order kinetics,” said lead author Daniel Kohane, M.D, Ph.D., director of the laboratory for biomaterials and drug delivery at CHB. "There may be applications in the third world, in places where storage of medication or availability of medications or physicians is restricted.”

While other drug-releasing contact lenses have been developed, none so far have been able to achieve a constant, steady release of substantial amounts of drug; typically, a burst of drug is delivered in the first few hours, followed by rapidly dwindling amounts that are too low to be therapeutic. This may cause toxicity, as well as hamper the drug's effectiveness.

Related Links:
Children's Hospital Boston
Massachusetts Eye and Ear Infirmary
Massachusetts Institute of Technology