Contact lenses will provide timed, targeted drug delivery

For decades, contact lenses have offered refractive correction, comfort, safety and convenience. The development of new materials and lens designs has spurred disposable and extended-wear lenses that provide value and efficacy.

Ongoing developments promise to yield soft contact lenses that also deliver medication to the eye for various conditions such as glaucoma, allergy, dry eye and infection. Research is yielding new materials and designs that may propel medicated contact lenses into the marketplace.

A decades-old concept

The notion of drug-eluting contact lenses is not new. According to a recent study published in the journal Seminars in Ophthalmology, the concept of drug-delivering contact lenses dates to 1965, when it was described in a patent for a soft contact lens.

Currently, the concept of contact lens drug delivery is of great interest to clinicians, the authors said. For example, they cited one study showing that, when surveyed, 93% of eye care providers stated that they would use a drug-releasing contact lens if it were added to their treatment arsenal.

The authors also cited an earlier study showing that though eye drops were the preferred drug delivery method for 90% of all ophthalmic medications, they were inefficient and ineffective. For example, only 1% to 7% of a medication in an eye drop is absorbed by the eye, even when it is administered correctly, the study showed.

The authors cited an earlier study showing that the cornea would absorb nearly 50% of a drug released by a contact lens. However, more in vivo research is needed to produce conclusive evidence, the data showed.

The authors pointed to two widely held basic approaches to impregnating contact lenses with medications: loading drugs onto or into a pre-formed lens or manufacturing a lens with the drug entrapped inside. Both approaches have been used with and without additional controlled-release technologies, the authors said, citing earlier research.

Development challenges

Designing a safe, effective drug-releasing contact lens poses several challenges. For example, a lens must be loaded with one or more drugs that can be released safely and effectively over a specific period of time. Also, a lens must offer optical clarity, refractive benefit, comfort, cost-effectiveness and a long shelf-life, the authors said.

Currently, there are no U.S. Food and Drug Administration-approved medicated contact lenses on the U.S. market. Johnson & Johnson is developing a contact lens that not only corrects vision, but also delivers medication to treat allergy symptoms in the eye, according to a company source.

Existing hydrogel lenses absorb medications but release them too quickly. Newer silicone hydrogel lenses release medications gradually but have a limited capacity for drug loading, the study authors said.

Prototype contact lens

A drug-eluting contact lens prototype has been designed to release glaucoma medication for 1 month or longer, Daniel S. Kohane, MD, PhD, the corresponding author, told Primary Care Optometry News. Dr. Kohane, of Children’s Hospital Boston/Harvard Medical School, and fellow authors developed the prototype and are obtaining patents for it.

“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. This means, basically, that the same amount of drug is released every day for a long period of time,” Dr. Kohane said.

The lens design and drug release concept are simple and straightforward, he said. “It is extremely simple conceptually … It’s like a sandwich,” Dr. Kohane said. “The contact lens is the bread and the hamburger is a polymer film that contains the drug.”

Gradual drug release prevents an initial “burst” of medication from being released, which may cause toxicity and hamper the drug’s effectiveness, Dr. Kohane said. “But in our case, the key finding … was that you have therapeutic levels of drug released for an extended period of time,” he said.

The lens platform may be configured to dispense medication for glaucoma, dry eye, allergic conjunctivitis and infection. In the latter example, the lens would offer therapeutic or prophylactic treament, Dr. Kohane said.

The lens is designed for extended use but could also be used for daily wear, he said.

Compliance, availability

Gradual drug delivery through a contact lens is a viable alternative to eye drops considering related compliance issues, Dr. Kohane said.

In addition, “there may be applications in the third world, in places where storage of medication or availability of medications or physicians is restricted,” he said.

Additional research

Ongoing research efforts elsewhere are focusing on other technologies. For example, researchers at the Institute of Bioengineering and Nanotechnology in Singapore are developing a drug-eluting contact lens with nanometer-sized channels that would regulate drug elution and minimize waste, according to a press release.

One U.S. patent application describes a contact lens that would provide zonal drug delivery. According to the application, submitted by Werhner C. Orilla and James A. Burke, the lens body would have an optical axis and an opaque simulated iris pattern containing the drug, which would be delivered in a fashion dictated by the iris pattern. This technology would also effectively regulate drug delivery, the release said.

Legislative issues

In anticipation of these types of contact lenses coming onto the market, optometrists in a number of states are pursuing legislative changes to ensure they will have the right to prescribe them. See “Maine ODs pass law to remove restrictions on prescribing,” and “Texas passes legislation that allows ODs to dispense therapeutic contacts.”

For more information:

• Daniel S. Kohane, MD, PhD, can be reached at Children’s Hospital Boston, Division of Critical Care Medicine, 300 Longwood Ave., Bader 634, Boston, MA 02115; (617) 355-7327; (617) 730-0453; e-mail: Daniel.Kohane@childrens.harvard.edu.

References:

• Ciolino JB, Dohlman CH, Kohane DS. Contact lenses for drug delivery. Semin Ophthalmol. 2009;24(3):156-160.
• Ciolino JB, Hoare TR, Iwata NG, et al. A drug-eluting contact lens. IOVS. Published January 10, 2009. Doi: 10.1167/iovs.08-2826.