Cure for colour blindness.

SCIENTISTS have cured colour blindness in monkeys, bringing hope to millions of human sufferers worldwide.

Researchers from Washington and Florida universities made the breakthrough with two squirrel monkeys using gene therapy.

Experts believe it has potential to treat adult vision disorders involving cone cells - the most important human vision cells.

Ophthalmic molecular geneticist Professor William Hauswirth said: "Although colour blindness is only moderately life-altering, we've shown we can safely cure a cone disease in a primate.

"That's extremely encouraging for the development of therapies for human cone diseases that really are blinding."

The finding is also likely to intrigue millions of people around the world who are colour blind - including about 3.5 million people in the United States, more than 13 million in India and more than 16 million in China.

The problem mostly hits men, leaving about 8% of white American men incapable of discerning red and green hues - important for everyday things like recognising traffic lights.

"People who are colour blind feel that they are missing out," said Jay Neitz, a professor of ophthalmology at the University of Washington.

"If we could find a way to do this with complete safety in human eyes, as we did with monkeys, I think there would be a lot of people who would want it.

"Beyond that, we hope this technology will be useful in correcting lots of different vision disorders."

Neitz and his wife Maureen trained two squirrel monkeys named Dalton and Sam to tell which colours they saw, using a standard vision-testing technique called the Cambridge Colour Test.

The tests are similar to ones given to children the world over, in which students are asked to identify a pattern of coloured dots. The researchers devised a computer touch screen the monkeys could use to trace the colour patterns. When the animals chose correctly, they received a reward of grape juice.

Gerald Jacobs, a professor of psychology at the University of California, who was not involved in the research, said: "There are still questions about safety, but in these monkeys at least, there were no untoward effects."

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