Why is cornea free of blood vessels?

• Position: Eyesight

Scientists at Harvard University's Department of Ophthalmology's Schepens Eye Research Institute and Massachusetts Eye and Ear Infirmary, Boston, say they are the first to learn why the cornea, the clear window of the eye, is free of blood vessels--a unique phenomenon that makes vision possible. The key, indicate the researchers, is the unexpected presence of large amounts of the protein VEGFR-3 (vascular endothelial growth factor receptor-3) on the top epithelial layer of normal healthy corneas.

According to the most recent findings, VEGFR-3 halts angiogenesis (blood vessel growth) by acting as a "sink" to bind or neutralize the growth factors sent by the body to stimulate the spread of blood vessels. The cornea long has been known to have the remarkable and unusual property of not having blood vessels, but the exact reasons for this had remained unknown.

These results not only serve to solve a profound scientific mystery, but hold great promise for preventing and curing blinding eye disease and illnesses such as cancer, in which blood vessels grow abnormally and uncontrollably, since this phenomenon, normally present in the cornea, can be used therapeutically in other tissues.

"This is a very...