Husband-and-wife team begin work on cure for colour-blindness

A husband-and-wife team of vision researchers have begun work on finding the world's first ever cure for colour-blindness, six years after they successfully treated the condition in a pair of squirrel monkeys in a groundbreaking 2009 ophthalmological study.

Last month Jay and Maureen Neitz, who are both professors of ophthalmology at the University of Washington, paired up with Avalanche Biotechnologies, a Californian company whose focus is on the treatment of eye diseases, to explore the use of gene therapy to fix the condition in humans.

One in 12 men is colour-blind, but only 0.5% of women. This is due to a trick of genetics: the two opsin genes that colour-blind people lack are carried on the X chromosome. If you are female, you have two X chromosomes – meaning that women have a back-up pair if one set doesn't work. But with men, if their X chromosome is faulty, they will end up colour-blind.

The couple first experimented on the squirrel monkeys because they lack a gene that allows colour-sensitive cells in the eye, called cones, meaning that like humans with colour-blindness, the animals can't distinguish between red and green hues.

They injected the monkeys' retinas with the genetic code in human eyes for red pigment, giving the monkeys an extra class of cone photoreceptor and thus allowing them to eventually see the whole colour spectrum.

Now the couple will begin applying what they learned with monkeys to colour-blind people, with testing on humans beginning as soon as in a couple of years' time. And they're confident a cure is possible. "I don't think there's any question that it will work," says Maureen Neitz.

Some people have achromatopsia – they can't see any colour at all. But it's very rare: one in every 33,000 people. Most people with impaired colour vision don't differentiate between green and red. Facebook is blue because co-founder Mark Zuckerberg is red-green colour-blind, and he says blue is "the richest" colour for him. Although the condition does not affect one's health per se, sometimes, there are tragic consequences of colour-blindness. One Of Jay Neitz's patients caused a fatal car accident because he couldn't see a flashing red light.

But now a debate is raging in ophthalmological circles about adding even more colours to our vision. Besides red, green and blue cones, 12% of all women are believed to have a fourth cone in their retinas. The extra cone is usually non-functioning, but a very few women, known as tetrachromats, have an active fourth cone and can see 100 million shades of colour – about 100 times more than the rest of us.

In 2010, the first such woman was found during a British study on the mutation and since more female tetrachromats have come forward, like Concetta Antico, an Australian artist based in San Diego. "The little stones jump out at me with oranges, yellows, greens, blues and pinks," she says. "I'm kind of shocked when I realise what other people aren't seeing."