LONDON: A protein that prevents blood vessels from forming in the cornea could become the basis of new treatments for cancer and macular degeneration, a leading cause of blindness in the elderly, scientists said on Wednesday.

The team of international researchers identified a protein called sVEGFR-1 and found that when levels are low, blood vessels begin to form in the eye, impairing vision.

They believe therapies that boost levels of the protein could prevent the formation of blood vessels, which are a component in the spread of cancers and the cause of macular degeneration.

"We have discovered what it is that keeps the cornea clear. It has no blood vessels — which allows us to see,"said Dr Jayakrishna Ambati, of the University of Kentucky in Lexington who headed the research team.

The cornea is the transparent front part of the eye. Scientists have wondered for centuries why it has no blood vessels.

What causes blood vessels to form is a fundamental question for vision and also for diseases like cancer.

"This finding teaches us what keeps the cornea clear and gives us the ability to exploit it in other diseases, both in the eye and systemically because now you have a protein that blocks blood vessel growth that the body itself makes,"added Ambati, who reported the findings in the journal Nature.

The lack of blood vessels has been perplexing researchers because the cornea contains vast amounts of a chemical called VEGF-A, which promotes blood vessel growth.

The new protein discovered by Ambati and researchers from the US, Japan, Italy and Australia provides the answer. It is produced in the cornea and acts like a mop, absorbing VEGF-A which would otherwise make blood vessels grow.