Specially designed contact lenses may soon help optometrists and ophthalmologists monitor high eye pressure that can lead to vision loss from glaucoma.

That’s the conclusion of researchers in Spain who reported the development of a prototype pressure-monitoring lens at the 2010 annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) held this week in Fort Lauderdale, Florida.

The pressure-sensing gas permeable contact indirectly measures intraocular pressure (IOP) by detecting changes on the surface of the cornea caused by the internal eye pressure. It does so with an incorporated sensor consisting of a polycarbonate film nanostructured with an organic molecular conductor, according to the researchers.

The sensor is capable of detecting IOP changes of less than 1.0 mmHg, they say. (Normal IOP is generally considered to be in the range of 8 to 20 mmHg.)

Pressure readings can be obtained in real time and collected in a computerized record.

Currently, the prototype pressure-sensing contact lens only has been tested with non-living pig eyes, but the researchers say the device can effectively monitor IOP and has the potential to someday be used to assist eye doctors in glaucoma treatment.

Drug-eluting contacts may soon be used to treat glaucoma, thanks in part to a breakthrough by researchers at the University of Florida in Gainesville.

The idea of using contact lenses that contain medicine to treat eye diseases such as glaucoma is not new. A major hurdle in the technology, however, has been finding a way to keep tears from washing away the medicine too quickly.

Anuj Chauhan, PhD, and colleagues may have found the answer — vitamin E. The researchers say that incorporating the antioxidant vitamin into the therapeutic contact lens makes the glaucoma medicine last almost 100 times longer than it does with current drug-eluting contacts.

Many ophthalmologists and optometrists feel medicine-containing contact lenses may solve a major problem in glaucoma treatment. Traditionally, eye drops have been used to apply glaucoma medicine to the eye. But many patients forget to use their drops as directed, which can cause the condition to progress, leading to serious vision loss, even blindness.

And even when eye drops are used as directed for glaucoma treatment, they often are not as effective as they should be. Some studies suggest that only about 1 to 5 percent of the applied drug reaches the target tissue in the eye, and the rest is distributed throughout the body by the circulatory system, possibly causing side effects.

Many eye doctors and glaucoma experts say the use of medicated contact lenses may eliminate these problems, leading to more effective glaucoma treatment.

A second possible benefit of adding vitamin E to medicine-containing contact lenses is that the vitamin may help prevent cataracts due to its antioxidant activity, according to the researchers. Vitamin E also blocks UV radiation, possibly leading to reduced eye damage from UV light.

Though the new vitamin E therapeutic contact lenses are not yet approved by the FDA, animal studies in beagle dogs are ongoing to determine the effectiveness of the lenses in treating glaucoma.

SOURCE:  Contact lenses loaded with vitamin E may treat glaucoma. (Press release issued by the American Chemical Society, March 24, 2010.)

Keratoconus, a degenerative eye disease, generally causes vision problems that cannot be adequately corrected with eyeglasses.

But specially designed contact lenses often provide excellent visual acuity for people suffering from mild or even moderate stages of keratoconus.

In the January 2010 issue of Optometric Management, Gregory W. Denaeyer, OD, reviews four contact lens strategies for correcting vision problems caused by keratoconus:

Specialty soft contact lenses. This option often works well for individuals with mild keratoconus. Several contact lens companies produce specially designed soft contacts to fit the steep curvature of mildly keratoconic eyes, and these lenses also can correct significant amounts of keratoconus-induced astigmatism, according to Dr. Denaeyer.

Bi-aspheric gas permeable contacts. Gas permeable contact lenses that are aspheric on both surfaces (bi-aspheric) offer two advantages for keratoconus patients. The aspheric back surface helps the lenses stay centered for a more comfortable fit, and the aspheric front surface helps reduce higher-order aberrations for sharper vision, Dr. Denaeyer says.

“Piggybacking” contact lenses. This strategy involve fitting a gas permeable (GP) contact lens over the top of a soft lens. The GP lens can be specially designed to provide optimal vision for the keratoconic eye, and the underlying soft lens provides a cushioning effect for greater comfort. The soft lens also may help improve the fit of the GP lens and protect the cornea from friction caused by the GP lens that could otherwise lead to corneal scarring.

Scleral contact lenses. Specialty gas permeable lenses called scleral contact lenses are much larger in diameter than regular GP lenses so they can vault over the entire cornea and rest on the white of the eye (sclera). The large size of scleral lenses reduces pressure on the cornea and enables the lenses to stay centered, even on highly irregular keratoconic eyes.

Eye doctors who can offer their keratoconus patients all four of these contact lens strategies will help improve the fit and comfort of their contacts and help provide optimum vision, Dr. Denaeyer says.

[Ed. note: Another strategy not discussed by Dr. Denaeyer is the use of hybrid contact lenses. Essentially, the center of a hybrid contact is a gas permeable lens and the peripheral portion is a soft lens. Special hybrid lens designs are available specifically for keratoconus.]

SOURCE:  Four strategies for keratoconus. Optometric Management. January 2010.

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.]