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Understanding How The Cornea Stays Clear

Diseases of the cornea are the world's second most common cause of blindness. The cornea is the transparent tissue covering the surface of the eye. When people have corneal problems, extra blood vessels grow, clouding the cornea, affecting vision.

Dr. Reza Dana, of the Massachusetts Eye and Ear Infirmary in Boston, says scientists have long wondered how the cornea can remain transparent at all, when there are so many blood vessels around it normally. "And why do blood vessels terminate so abruptly," he asks, "as one can even see with the naked eye? You look at the eye, you see all the blood vessels in the conjunctiva, they come abruptly to an end when you hit the cornea, so no one really knew why that was the case."

Dana was surprised to find that the cornea had a large number of receptors able to capture a protein in the blood that usually promotes blood vessel growth. When the protein can't reach the right receptor, blood vessels are unable to develop. Dana likens the receptor to a lock and the protein to a key. "It's kind of like a key that's programmed, if you will, to go down the hallway and fit into specific locks on specific doors and the hallway is just packed with other locks and it just loses its way and never makes it to its target."

Dana says knowing how the body keeps the cornea clear could lead to new treatments to arrest eye disease, "seeing whether we can use this same receptor in other tissues in and around the eye to suppress the growth of blood vessels." Dana says the same technique might also be used to suppress the development of blood vessels in cancer tumors.