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New Corneas in Sight?
25 August 2010 2:00 pm
At least 8 million people worldwide could see again with new corneas, the thin, clear layer of collagen and cells at the front of the eye that helps it focus. But most never get transplants. A few years ago researchers developed biosynthetic corneas and now, 2 years after implanting them into patients, they appear safe and have helped several people see more clearly.
Millions of people worldwide suffer clouding of the cornea, caused by infections or trauma to the eye that leave them blind or with very impaired vision. There aren’t enough donor corneas from cadavers to go around, however, and those available are expensive: They cost about $2500 each (which doesn't include the cost of surgery), in part because they must undergo lots of testing for viruses and other contaminants before they can be put in. “In the developing world, that is forbiddingly high,” says Claes Dohlman, an ophthalmologist at the Massachusetts Eye and Ear Infirmary in Boston. Artificial corneas, which are made of plastic, aren’t easy for surgeons to work with, and carry a risk of complications such as glaucoma or infection.
“We wanted something that behaves just like a human tissue, so that the surgeon would be able to transplant it without any additional training,” says May Griffith, an applied cell biologist at the University of Ottawa in Canada and at Linköping University in Sweden.
For that, Griffith and her colleagues turned to collagen supplied by the company FibroGen in San Francisco, California. In the lab, Griffith’s team molded the collagen into the right curved shape and then enlisted eye surgeon Per Fagerholm of Linköping University to implant these lab-made corneas into 10 patients who had keratoconus, a condition that causes the cornea to deteriorate, or corneal scarring.
The big first test was safety, and the implants fared well. Patients' immune systems did not reject the new cornea, nor did any patient develop infections. The team also found that over time, the implants helped nerves in the area regenerate, leaving the volunteers with what looked like healthy eye tissue. Six patients saw somewhat better with their new corneas, based on astigmatism and visual acuity, like that measured in an eye exam, Griffith and colleagues report online today in Science Translational Medicine.
Griffith says it's too early to say what the implants will cost. And there’s still work to be done to make them more effective. The sutures used to attach the implant cause its surface to be a little bumpy, making it more difficult to restore vision. Contact lenses helped this problem and improved the patients’ vision to a mean of 20/42, similar to standard cornea transplants. Griffith and her colleagues are planning a larger study with what they hope will be better implants that don’t require sutures.
The corneas “will be, I think, of considerable use,” says Dohlman, who was not part of the research team. They could be mass produced and would almost certainly be far less expensive than donor corneas. “You could manufacture a square meter, test it once [for contamination], and then punch hundreds and hundreds” of holes in it to create a batch of new corneas, he says.