Scientists have cured colour blindness in monkeys in a world first.
As well as allowing colour-blind humans to tell red from green, the innovative technique could restore sight to the blind.
Sufferers of age-related macular degeneration – the most common cause of blindness in the elderly – are among the millions who could eventually benefit.
Researcher Jay Neitz said: ‘If we could find a way to do this with complete safety in human eyes, as we did with monkeys, there would be a lot of people who would want it.
‘We hope the technology will be useful in correcting a lot of different vision disorders.’
Professor Neitz used gene therapy – injections of genes – to allow two male squirrel monkeys called Sam and Dalton to see in full colour for the first time.
Like some humans with red-green colour blindness, the monkeys lacked a pigment that the cones – the colour-detector cells at the back of the eye – need to see red and green. As a result, they saw both red and green as shades of grey. Other colours, such as orange, blue and brown appeared washed-out.
To fix their vision, the U.S. scientists injected their eyes with millions of copies of a gene needed to make the missing pigment, the journal Nature reports.
The therapeutic genes contained the necessary DNA code to enable the light-sensing cells to distinguish between red and green – something lacking in the male monkeys.
Tests revealed the gene therapy was a success. The male monkeys now possessed the necessary photopigments to see all colours and were able to correctly pick out red from green on computer image tests.
The monkeys were treated over two years ago and their improvement in colour vision has remained stable since.
Professor Neitz’s team will continue to monitor the animals to evaluate the long-term treatment effects.
They are hopeful that a similar therapy could benefit people who are colour blind.
“This provides a positive outlook for the potential of gene therapy to cure adult vision disorders,” they said.