New synthetic cornea appears to be as good as the original

William Atkins
Friday, 31 August 2007 01:57

Science - Health

Researchers at Stanford University, in California, have developed an artificial cornea for the eye from polyacrylic acid and polyethylene glycol that seem to work as well as a natural cornea.

The mixture is a biomimetic material (that is, an artificial product produced from a natural one) that is a hydrogel, or a polymer that holds water in a very efficient way.

One part of the hydrogel is molecules of polyacrylic acid, which is a polymer that absorbs water. Polyacrylic acid is also used as part of the ingredients in the fluffy material that is found in the middle layer of today's diapers.

Molecules of polyethylene glycol (PEG) are the second part of the hydrogel. PEG molecules resist the gathering of surface proteins that can eventually cause inflammation on and around the cornea. PEG also absorbs water, and it is commonly found in foams such as foam rubber and fibers such as spandex.

The resulting mixture is about twenty times stronger and flexible then either polymer used separately. Such was the problem earlier in the attempts to make artificial corneas: all of the polymers made were not permeable enough and strong enough to make a synthetic cornea that would perform as well as the real thing. The transparent hydrogel material is permeable to nutrients such as glucose, which is one of the nutrients that the cornea needs to remain healthy.

The researchers for this new artificial cornea include Curtis Frank and fellow associates as Stanford University in Stanford, California. They presented their finding at the American Chemical Society meeting at Boston, Massachusetts on Monday, August 20, 2007.

If the new material is approved for use in the United States, it could potentially allow million of people to see, who now have damaged corneas. Currently, this number of people is hoping for a corneal transplant, but cornea transplant donors are few and far between.

According to the World Health Organization (as taken from the New Scientist article “Replacement cornea makes clear difference”, August 25-31, 2007, page 28), about one hundred thousand people worldwide receive cornea transplants each year, however, more than ten million people do not receive such transplants and remain blind due to their own damaged corneas and the lack of availability of proper replacement corneas.

However, donor corneas also have difficulties. About 20% of the transplants are rejected by the recipient. Those that are successfully transplanted take about six to twelve months for a complete visual recovery.

The researchers hope their discovery will provide a better and more readily available alternative to donor corneal transplants and a safe and effective alternative to living with a damaged cornea.