Drug-eluting contact lenses may be the way of the future for the delivery of certain eye medications, according to two researchers involved in developing the lenses.

In this month’s issue of Expert Review of Ophthalmology, Harvard Medical School researchers Joseph B. Ciolino, MD, and Daniel S. Kohane, MD, PhD, discussed some of the advantages and challenges of developing these lenses.

It’s estimated that 90 percent of eye medicines are delivered to the eye in the form of eye drops. But many people have difficulty properly applying eye drops to their eyes, and less than 10 percent of the medicine in eye drops is absorbed by the eye, according to research cited by Drs. Ciolino and Kohane.

Other studies have shown that poor compliance with prescribed eye drop medications is a significant problem in the management of chronic eye diseases, such as glaucoma and ocular hypertension.

Drug-eluting contacts could improve patient compliance with their glaucoma treatment, and a sustained release of medications may prove more effective than the short bursts of the same drugs when they are administered via eye drops, the researchers say.

However, challenges to creating drug-eluting contacts include:

• The drug contained in the contact lens must not compromise the optical quality of the lens.
• The drug must not reduce the biocompatibility of the lens. (In other words, the drug must not make the lens more difficult to wear or increase the risk of eye problems such as a corneal ulcer from wearing contacts.)
• Extended release of the drug cannot be toxic to the cornea.
• The drug should not affect the physical characteristics of the lens, including its thickness and oxygen permeability.

Other design challenges include determining how much of the drug the contact lens should contain and how long the release should last.

Also, drug-eluting contacts could complicate contact lens care. Ideally, the lenses should release their drug load only when they are on the eye, not during cleaning or storage. (It’s possible that developing drug-eluting daily disposable contacts may solve this potential problem.)

Finally, it will be important to determine the cost-effectiveness of drug-eluting contacts compared with conventional treatment of glaucoma and other problems with eye drop medications.

Despite these challenges, the researchers say drug-eluting contact lenses offer the possibility of better compliance with prolonged treatment of chronic eye diseases and relief of certain eye symptoms from a single application, giving eye doctors a new and more effective means to treat ocular diseases and conditions.

[Ed. note: To date, drug-eluting contact lenses are not FDA-approved for use in the United States.]

In today’s issue of Contact Lenses Today, optometrist and contact lens specialist Morris Lehrfeld, OD, shares the following tips he gives to his patients to help keep their eyes healthy when wearing contact lenses:

1. Use only solutions prescribed by your eye doctor. Older and generic contact lens solutions can cause compatibility issues, especially with modern silicone hydrogel contacts, says Dr. Lehrfeld.
2. Use fresh contact lens solution every day. Many contact lens wearers are guilty of “topping off” the contact lens solution left in their lens case from the previous day. This reduces the effectiveness of the disinfection process, potentially leading to serious contact lens-related eye infections.
3. Replace your contact lens case at least every three months. Even with proper lens care, bacteria and other infection-causing agents can accumulate in contact lens cases over time. Routine replacement of your lens case can reduce the risk of contamination and eye infections.

Dr. Lehrfeld is an eye care provider at Palatine Vision Center, a group optometric practice in Palatine, Illinois. Contact Lenses Today is a weekly e-mail newsletter for eye doctors sponsored by the professional journal, Contact Lens Spectrum.

Diabetics may soon have a painless and more convenient way to monitor their blood glucose levels — glucose-monitoring contact lenses.

The contact lenses change color in response to elevated blood glucose levels, alerting diabetic contact lens wearers to the need for medication. It is hoped that the lenses will help diabetics more effectively manage their disease and possibly avoid sight-threatening diabetic retinopathy and other complications of diabetes.

The special soft contact lenses are being developed by Chemical and Biochemical Engineering professor Jin Zhang at the University of Western Ontario (London, Ontario, Canada).

The non-invasive technology uses microscopic “nanoparticles” that can be embedded into hydrogel contact lenses. The tiny particles react with glucose molecules present in tears, and this chemical reaction changes their color, which then causes the contact lens to change color.

Professor  Zhang recently received a grant from the Canada Foundation for Innovation (CFI) to further develop this and other technologies using multifunctional nanocomposites (films embedded with reactive nanoparticles).

Other possible applications include nanocomposite films for the food packaging industry that can better prevent meat and other foods from spoiling and can make the packaging more biodegradable than regular plastic wrap, according to a press release issued today by the university.