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Replacement Cornea Makes
Clear Difference
An artificial cornea has been created that is as strong and clear
as the real thing.
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. 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.
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
nutrients to the epithelial cells.
(Ref: NewScientist dated 25,
October 2007)
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