Closer to fooling the eye

But when a cornea becomes cloudy or scarred from disease, injury or infection, the path of light into the eye can be distorted or blocked, resulting in blindness.

Transplanting human corneas from cadavers can restore someone's vision. But because of a tissue shortage, only 100,000 corneal transplants are performed worldwide annually -- serving just 1% of the 10 million people who are stricken with corneal blindness. This shortfall, as well as problems with such transplants even when available, has spurred the quest for an artificial version of one of nature's masterpieces.

"The holy grail is a synthetic implant that is as strong, clear and flexible as a natural cornea, that would fully integrate into surrounding tissue and last forever," says Jean-Marie Parel, head of the Ophthalmic Biophysics Laboratory at the Bascom Palmer Eye Institute in Miami. "That way, we could implant this at any time, day or night, without having to hope that someone died."

Bioengineers are making significant progress. They predict that within a few years we could have cornea substitutes that slip over the surface of the eye as easily as contact lenses and mesh neatly with surrounding tissue to form a protective barrier against the outside elements.

Such devices would be of great use even in the U.S., where the shortage of corneal tissue isn't critical but where other problems exist. More than 46,000 Americans undergo cornea transplants each year. They must use steroidal eye drops (which have side effects) to prevent tissue rejection and endure a lengthy recovery period of up to six months; sometimes they are left with astigmatism, an uneven contour of the cornea that causes blurriness. Up to 10% of corneal transplants fail.

The new devices are also expected to improve on two artificial corneas that are already approved by the Food and Drug Administration: one called the Dohlman, developed at Harvard University, and a newer one, the AlphaCor, created by Australian scientists. In both cases, patients can develop inflammation and infections, and sometimes the devices pop out. In the case of the Dohlman implant, human donor tissue is required. For these reasons, they are used only as a last resort for people who have repeatedly rejected natural corneas or who can't receive donated tissue because of severe eye diseases.