June 23, 2010 -- More than 1.2 million Americans suffer cornea damage from injuries and more than 40,000 people a year undergo cornea transplants to repair otherwise irreversible eyesight damage, according to the American Academy of Ophthalmology.
But now, a new study suggests that many who suffer corneal damage by chemical burn may successfully restore their sight with transplants from their own eye stem cells.
Researchers in Italy studied a technique to repair damaged corneas by using patients' own unscathed limbal stem cells -- found at the edge of the cornea -- to grow new tissue that was then grafted into the patient's own eyes. The experiment was tried on 112 patients with corneas damaged by chemical burns. It was successful in 78 percent of patients, according to researchers, who followed the patients for 10 years after the procedure.
A corneal transplant involves removing the central part of the diseased cornea _ called the button -- and replacing it with a donor's button. It is similar to other transplants -- and the donor's body must match the recipient's to avoid rejection. The study published in the New England Journal of Medicine suggested a way to bypass the need for a donor match.
"Knowing that this type of procedure can sustain over a long period of time is the highlight," said Dr. Stephen McLeod, professor and chairman of the department of ophthalmology at the University of California in San Francisco, and a scientific committee board member at the nonprofit organization Prevent Blindness America. "This is the largest longest study [on limbal stem cell cornea transplants] so far."
The Potential to Save Sight
Corneal injuries and diseases are the leading cause of visits to eye care clinicians, according to the National Eye Institute, an arm of the National Institutes of Health.
According to Dr. Sreedhar Potarazu, an opthamologist and CEO of VitalSprings, a health information technology company in McLean, Virginia, limbal stem cell transplants may have the potential to repair damaged corneas in workers who are at risk for chemical burns to the eyes, such as oil spill relief workers in the Gulf of Mexico who may be exposed to oil fumes and dispersants.
"Sometimes on television you can see people in the area where these chemicals are and they're not wearing goggles," said Potarazu. "These and others could turn into potential candidates."
More than 4,000 Americans suffer from chemical burn eye injuries in the workplace each year, according to the U.S. Bureau of Labor Statistics.
Besides chemical burns, cornea transplants are also performed for other injuries to the cornea, as well as side effects from inflammatory diseases such as lupus or shingles.
The stem cells work by regenerating the outermost layer of the cornea, which is often where cornea damage occurs, said McLeod.
According to the study, one research recipient who had been blind for 50 years could see within a year after the procedure.
Like skin cells, limbal cells continuously grow, die, and fall away. The challenge of using limbal stem cells is making sure there is a good combination of immature and mature cells, so the new tissue is able to sustain over time, said Potarazu.
"When you do a stem cell graft, you have to have enough of the cells on reserve to regenerate, because they can slough off quickly," he said.
"We put a lot of effort in developing, in checking several parts of the process of the construction, and to monitor each percentage of stem cell maintained in each part of the process during amplification," said Graziella Pellegrini, one of the authors of the study.
While it's still too early to be certain, this research suggests that someday it may be possible to use stem cells to treat other critical parts of the eye, such as the retina, said Potarazu.
"If the nerve cells are dead [and that's what's causing blindness], it's difficult to regenerate that," he said. "But where there is the potential for tissue that's on the brink of recovery, that's not all dead, then there's potential [to research stem cells]."
For Dr. Ivan Schwab, professor of opthamology at the University of California Davis School of Medicine, the possibilities broaden beyond the eyes.
"This could extend to internal organs, like the liver. We may learn techniques from this work that apply to liver bioengineering and regrowth. Very exciting times, for all physicians," said Schwab.
Although the procedure is still at the research stage, many experts said that this approach to blindness may someday save many patients' eyesight.
"Imagine how excited you'd be if you didn't have sight one day, and then within a matter of a few weeks or months, you had sight again," said Schwab. "It's very exciting. For an ophthalmologist, it really is as good as it gets."