We shouldn’t turn a blind eye to colour deficiency

There will always be some children who colour their skies purple, tree trunks red and hair green.

Colour deficiency is not rare. It affects one in 12 males. The most severe forms can impede children in their early school years or block off certain careers.

A young child cannot tell you what it is not seeing, and there is no screening in schools for this inherited condition.

At the National Optometry Centre in Dublin Institute of Technology, Dr Peter Davison assesses adults and children for colour deficiency. He doesn’t call it colour-blindness: colour deficiency is more accurate.

He recently tested a primary-school boy who had difficulties seeing red and green markers on the board of his new school. Colour deficiency is usually detected in children and adults after they fail the Ishihara test, which was designed in 1917. The test is sensitive but imperfect.

“It gives a poor indication of how severe the problem is, and colour vision can be anything from almost normal right up to black and white vision, although that’s extremely rare.”

Davison carries out a battery of tests in his clinic to grade severity and type. He recommends that concerned parents first visit an optician or optometrist for a simple test. The cause is a fault in the red, green or blue cones in the retina of the eye.

The most common type of colour deficiency happens when the green-sensitive cones in the retina are faulty and there is reduced sensitivity to green light. This is called “green-weak” and makes up two-thirds of cases. Or you can be red-weak: “[In this case] there will be some confusion of reds, yellows and greens, but if there is enough difference in the colours, they will be seen,” says Davison.

The two more severe forms happen when the red- or green-sensitive cones are completely non-functioning (red- or green-blindness). “For red-blind and green-blind people, discriminating between green, yellow and red is wiped out, and they will distinguish these colours only on the basis of brightness. But they can be utterly confused,” says Davison.

Not seeing red

If you are red-blind, you might not be able to see red at all. For the two severe forms, one in 50 males are affected: about 50,000 males in Ireland. Those with severe colour deficiency will find it difficult to distinguish the jerseys of Ireland, Wales or New Zealand if they line up on the rugby pitch.

Schools and teachers here are given little information about how to identify or deal with colour-deficient children. It is the same in the UK.

“Colour-blind children are pretty much ignored in schools, but they should be diagnosed at an early stage,” says Kathryn Albany-Ward, who realised her son was severely colour-deficient when he was seven. He complained that he couldn’t tell who was on the team of his new school during games; the sports tops were maroon and olive green.

“I didn’t think of those colours as red and green, but they sort of are,” she says.

When she realised how little information was available, she set up Colour Blind Awareness, a UK nonprofit, with a great website, colourblindawareness.org.

“The most obvious thing colour-blind children do is innocently colour pictures with inappropriate colour choices,” she says. Labelling colouring pencils with symbols and giving teachers and parents information can help a lot.

“Teachers should be trained how to spot it in the classroom and work out how to use educational resources so colour-blind children can see the information.”

People often don’t realise how severe it can sometimes be or that such children might not be able to tell red and black apart. The Ishihara test often flags a problem, but it is possible to fail this test and still have adequate colour vision.

The most sophisticated of Davison’s tests involves an anomaloscope, which resembles a single-lens microscope. It requires you to look down the scope and mix red and green light to generate a half-circle of yellow to match a reference yellow half-circle. Those who are green-weak will put far more green into the mix than colour-normal people. “Those with a severe problem will use any mix of red and green to match the yellow.”

Davison’s clinic can diagnose severity and type of colour deficiency. There is no proven treatment, he says, although sometimes a red colour filter can help, because it changes the contrast between colours.

• dit.ie/national-optometry-centre 
• colourblindawareness.org

VISION OF THE FUTURE: POSSIBLE CURES

A Californian start-up called EnChroma offers glasses for children and adults that can assist in red-green colour deficiency. These can be prescription or nonprescription, ordinary lenses or sunglasses.

“If you selectively filter out wavelengths of the light, you can re-create the proper separation between the red and green photopigments,” says cofounder Donald McPherson.

McPherson has a PhD in glass science and is the company’s chief scientist. He founded EnChroma after doing research funded by the National Institutes of Health in the US.

They have had positive reactions on social media, although the company notes that the glasses are unlikely to work for certain types of colour deficiency, including the most severe forms.

Also, many experts in the field remain sceptical that they offer a cure of any sort, although they might help with contrast.

Another ambitious approach in the US seeks to use gene therapy. The plan here is to insert functioning photopigments into the eye of volunteers to “cure” red-green colour deficiency.

Scientists have succeeded in giving male squirrel monkeys full colour vision by transferring a gene into their eyes using a virus. However, no such progress has been made for humans.

Peter Davison at the National Optometry Centre in Dublin says scientists in the field are dubious about the gene-therapy approach and that it is too early to say how viable this will be for humans. He adds that there are no published scientific studies on the EnChroma glasses.

In September a UK firm (eyeteq.spectraledge.co.uk) unveiled technology for televisions to allow colour-deficient viewers to differentiate between colour combinations they struggle to see, offering hope especially to sports fans and gamers.

Kathryn Albany-Ward has had contact with Fifa and Uefa and says they have promised to make jerseys friendlier to the colour-deficient.