Their dome-shaped eyes are packed with multiple tiny eye elements topped with corneal lenses.
And some people develop problems following transplants, such as rejection of the new corneal tissue.
After two unsuccessful corneal transplants, he underwent a pioneering stem cell operation that restored his vision.
In modern times, there have been cases of vision restored thanks to corneal transplants and cataract surgery.
The procedure, which was performed by Boxer Wachler, is a new technique known as corneal cross-linking.
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However, the long-term effects of genetically changing the behaviour of certain corneal cells is not yet known.
Even in the UK, where there is an established organ donor scheme, there is still a shortage of corneal tissue for transplantation.
Many are needed because of keratoconus, a disorder of the shape of the cornea, or corneal disease, often caused by cataract surgery.
Alan Matthews, 67, who sufferers from a condition called fuchs corneal dystrophy, was the first to benefit and is already literally seeing the benefits.
Some corneal cells rarely, if ever, reproduce through the course of a lifetime, and inducing cell division could result in a cancer-like condition of uncontrolled growth.
Professor Colin Kirkness, a vice-president of the UK Royal College of Ophthalmologists, said that worldwide, the development of an artificial corneal held the potential for great benefit.
"Unlike other organs, which must be donated immediately, corneas can be donated up to 24 hours after death and there is no upper age limit on corneal donation, " a trust spokesman said.
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