AN ARTIFICIAL cornea has been created that is as strong and clear as the real thing. It could allow millions of people with damaged corneas to see.
Corneal blindness can be caused by disease, injury or infection of the eye’s clear surface. It can be cured with a transplant from a human donor, but donors are scarce. The World Health Organization estimates that 10 million people worldwide are blind because of defective corneas, yet only 100,000 receive transplants each year.
Artificial corneas made from flexible hydrogels – polymers that absorb water – are now available, but they are not permeable enough to support epithelial cells on their surface. These cells guard against bacteria and stop natural corneas becoming cloudy, by preventing proteins from sticking to them. Adding more water to the hydrogels allows glucose to diffuse through them and nourish epithelial cells on the surface, but it also weakens them. So there is a push to develop a synthetic cornea that is both strong and permeable. “The long-term goal is an off-the-shelf cornea that looks and acts like donor tissue,” says Heather Sheardown of McMaster University in Hamilton, Ontario.
Now Curtis Frank and colleagues at Stanford University in California have done just that. They took polyacrylic acid, the water-absorbing polymer found in diapers, and cross-linked it with polyethylene glycol, which also absorbs water. The cross-links mean that the resulting material is 20 times stronger than either of the starting polymers on their own, and about the same strength as a human cornea. Crucially it also has the same water content as a real cornea, which greatly increases its ability to transport ...