Eye surgeons — and some of their patients — may soon be seeing more light at the end of the tunnel.
In a pioneering technique, two separate research groups announced today they have successfully restored eyesight to patients with severely damaged corneas, using bioengineered tissue grown in a laboratory and then transplanted onto the eye.
The two teams of researchers — one out of Taiwan reporting in the New England Journal of Medicine and the other from University of California at Davis Medical Center reporting in the journal Cornea — announced they used the technique to improve vision in a total of 15 patients.
How to Grow a Cornea
They first took corneal stem cells, or immature cells that have the ability to generate mature cornea cells, and cultivated them in petri dishes to grow replacement corneas. Then they stitched the newly created corneas onto their patients’ eyes. A significant factor in the researchers’ success was growing the corneas on a scaffold of amniotic tissue, also known as afterbirth material.
“The real power of this technique is where it leads us,” says Dr. Ivan Schwab, professor of ophthalmology and a co-author of the Cornea study. Schwab says that the cornea may be the next bio-engineered tissue in a list that already includes skin and cartilage, and could someday include the lungs, bladder, and intestines.
The cornea is the clear, dome-shaped surface that covers the eye and allows light to pass through. When it becomes damaged from disease, such as the rare Stevens-Johnson syndrome; an accident, such as a splash of acid to the face; or an infection, it can become scarred and cloudy, impairing vision.
Prior Donors: Corpses
Conventional corneal transplants, which use donated corneas from a corpse, are the most commonly performed transplant surgery, with almost 46,000 done last year, according to the Washington D.C.-based Eye Bank Association of America. Eye banks nationwide collect corneas from donors upon their death, often by registries posted on the back of one’s driver’s licenses, and distribute them to needy patients within a few days.
Around 90 percent of these surgeries are successful, but for a handful of patients, even repeated transplants fail.
Those are usually patients who have sustained damage to or lack their crucial “corneal stem cells,” Schwab says. These cells, which lie deep within the cornea, act as “mother cells,” replacing damaged layers of the cornea with fresh cells, much like the skin. (Corneal stem cells are not the same as the controversial fetal stem cells.)
Without a source of stem cells, a transplanted cornea will not be able replenish itself with healthy new corneal cells to sustain clarity.
Promising New Methods
“For years, we didn’t have anything to offer these patients — we’d transplant a cornea, it would work for a few weeks, then the blindness would return. It’s devastating,” says Dr. Edward Holland, clinical professor of ophthalmology at the University of Cincinnati and director of cornea services at the Cincinnati Eye Institute. “This [research] takes the stem cell procedure to another level, giving us more options to offer [these] patients.