THE man steps out onto the garden deck, where his family hands him a gift. “Open it!” they shout, from behind the video camera. After fumbling with the wrapping, he pulls out a pair of dark glasses. When he tries them on, his jaw drops. He slowly moves his gaze from the grass to the trees to the pots of flowers. He lets out a few hushed “wows”. Eventually, he removes the glasses to wipe tears from his eyes.
This video is one of thousands like it that have appeared online over the past few years after a pair of glasses hit the market that promise to let colour blind people see what they have been missing. Elsewhere, scientists working on a more permanent treatment for colour blindness have witnessed a similar fervour. “I’ve gotten thousands and thousands of emails. I still get people who write or call me and say they want to be the first human being who gets treated,” says Jay Neitz at the University of Washington in Seattle, who has been working on a gene therapy.
Around the world, 300 million people lack full colour vision. For most, from the moment they first opened their eyes as newborns, they saw the world with a different palette to others. And I am one of them. So when I discovered the hype around the glasses, I had to try them. But this obsession over a way to correct colour blindness also got me thinking. How big a problem is colour deficiency really? And do we actually want to treat it?
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Humans see in colour thanks to cone cells in the retina. There are three types of these cells, each tuned to different wavelengths of visible light that roughly correspond to what we see as three colours: blue (short wavelengths), green (medium) and red (long). In most people, the brain uses the output of the cells to process a full spectrum of colours. These individuals are called trichromats. But 1 in 12 men and are affected by colour blindness, of which there are several kinds. It affects more men than women because the faulty gene responsible is passed on via the X-chromosome – so women need two copies to have the condition, otherwise their unaffected X-chromosome can compensate.
Total colour blindness, where the cones don’t work at all and the world appears only in shades of grey, is extremely rare. Then there is dichromacy. Here, one type of cone is lost, leaving these individuals only able to see the world in combinations of two colours instead of three. The chemist John Dalton was one of the first to describe this condition, as he couldn’t see red at all. He suspected a discolouration of the fluid in his eyes was filtering out red light, and asked for them to be examined upon his death. No tinge was found, but his name lives on in many languages, where the inability to distinguish red from green is known as daltonism.
“Putting the glasses on is like applying an Instagram filter. Without them, the world feels drab”
Even more common is for signals from the cone cells to be diminished but not entirely absent. Most of those who identify as colour blind can in fact see a full range of hues, but not quite in the same way as everyone else. Some will appear less vibrant. Many people don’t know they have the condition until adulthood, when they have their colour vision tested as part of certain job applications.
Often, this variant is due to too much overlap between the wavelengths picked up by the red and green cones. As a result, the two colours aren’t seen as separate and people struggle to distinguish subtly different shades. This is known as anomalous trichromacy, and makes up the bulk of colour blindness.
I have the most common subtype of this variety, deuteranomaly, which means I have a reduced sensitivity to green light. Shades that contain a blend of red and green take on a muddy hue. Deutans, as we are known, also confuse shades of purple.
Keen to see where I’ve been going wrong, I arrange to be sent a pair of the glasses by Enchroma, the company that makes them. But when they arrive, I find myself hesitant to put them on. After all, I just decorated this apartment. What if I discover my carefully balanced colour palette resembles an Austin Powers motif? And home decor aside, I’m still not sure why there’s such a demand for colour-correcting specs.
According to Neitz, for many of those who write to him, it comes down to career choice. Colour deficiency can still exclude you from a surprising number of professions. Airline pilots, air traffic controllers, police officers, firefighters, train drivers and many others must pass colour-vision tests to be certified in several countries. And when I hear about the lengths to which some people will go to pass these assessments, I start to understand the enthusiasm for a fix.
You may be familiar with the Ishihara test, where numbers are hidden in plates of coloured dots, but the system isn’t perfect. “If you insist on zero errors in the Ishihara complete edition, about 20 per cent of people with normal vision will fail,” says , who studies optics at City, University of London.
So Barbur developed the more advanced , . It uses blocks of colour that move across a background of sparkling pixels, similar to static on an old TV.
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As companies switched to using CAD, Barbur found that some of those who had previously passed workplace Ishihara tests were in fact colour deficient – sometimes markedly so. This wasn’t just down to the test’s fallibility. “When you have a job that pays €150,000 a year, and when that job depends on your colour vision, you will make use of any possible cues to ensure that you pass the test,” says Barbur.
One popular trick is to memorise the complete set of Ishihara plates, recognising them by the pattern of dots instead of the colours. In the CAD test, it is impossible to use any other visual cues except colour vision to spot the blocks.
Another trick is to smuggle in coloured contact lenses. These would impair the person’s eyesight in general, but can help them pass the test. This doesn’t work for CAD, though.
Of course, there are other reasons for wanting to see the full spectrum of colours. “I get a lot of people [contacting me] who have some sense that they’re missing out on the aesthetics of having colour vision,” says Neitz. I can understand this: I’ve never wanted to be a pilot or a police officer, but I, too, am curious to know what I’ve been missing.
So I open the box. The glasses look like regular shades. At a glimpse, the lenses seem to paint things rose pink. I walk onto my roof terrace and slip them on. “Huh,” I say to myself. “Huh.”
Putting them on feels a little like applying an Instagram filter. Contrast increases and details are easier to pick out, especially in the trees below. Colours feel more intense, saturated. The sense of everything being rose-tinted soon passes as my eyes adjust their white balance. Shades of red are lustrous. A red towel hung out to dry on a balcony flares angrily. Even when I leave to walk through the shady alleyways of Barcelona, a red motorcycle gleams with a fluorescent hue in the gloom. Without the shades, the world seems rather drab.
New shades
Glass scientist Don McPherson co-founded Enchroma in 2010, after the serendipitous discovery that lenses he was developing to protect surgeons’ eyes from medical lasers also enhanced colour perception in those who were colour blind. The reason was that coloured filters can make certain hues pop out against the background. Looking through a pair of bright pink lenses, for example, will make reds appear more vibrant – albeit at the cost of turning greens almost black.
This effect has been recognised for over a century, and many other companies offer tinted lenses to address colour deficiency. McPherson says it is the ability of Enchroma’s glasses to bring relevant colours to the fore without diminishing others that stands them apart, making them worthy of their hefty price tag. They do this by filtering out the light wavelengths that trigger both red and green cones, essentially removing the colours that my eyes get easily muddled over.
A pair of such glasses could certainly have saved me embarrassment during my early years, when I frequently confused one crayon for another. They might also stop me buying grey shirts that turn out to be a wan shade of green, or struggling to know when meat is cooked.
Later that evening, I pop mine back on to watch the sunset from the roof. The blank lemon-yellow sky is transformed into a fiery landscape, streaked with blazing reds. My jaw drops – this really is breathtaking. But is it any more true to life than the ochre sunsets I’m used to? Visually, I don’t perceive anything “wrong” with my usual field of view – those who are visually impaired in some way from birth never do. So while it is fun to try the glasses, I don’t think I would miss them that much.
Still, for others with more extreme forms of colour blindness, a more permanent solution has appeal (see “Permanent fix”). As part of my research, I spoke to Arthur Collyer, who has only ever seen in black and white. He tells me he would be interested in a gene therapy. “I’ve never seen colour, so I don’t know what I’m missing,” he says, “but it does prevent me from doing a lot of things.”
We may want to approach a cure with caution, however. Seeing new colours doesn’t necessarily mean enjoying it, says Ken Knoblauch of the Stem-Cell and Brain Research Institute in Lyon, France. He himself has a lack of cone cells that leaves him with a sharply diminished sense of red. “History is chequered with accounts of restored vision not holding the hoped-for promise,” he says.
Knoblauch says that having learned to distinguish objects by other means, having a new channel of colour might confuse more than assist. “Would it be ugly to see the colour, would it get in the way of existing perception?” Both Knoblauch and Barbur point out that there is no fundamental normal standard of colour vision, and variability exists even among trichromats (see “Do you see what I see?”).
Even so, a permanent change may be nearer than we think. While McPherson is keen to emphasise that his firm, which is now working on contact lenses that offer the same visual adjustment as its glasses, doesn’t claim to treat or cure colour blindness, he tells me that some customers have reported the corrective effect of the glasses seems to persist even when they take them off. It might be that wearing them mimics the brain’s development of colour vision, he says. “Now you know what purple looks like, you can perceive it.”
A week later, I find myself cruising at 30,000 feet, glasses stowed away, when the setting sun slices through the cabin windows, igniting everything it touches. I hold my hand out in front of me, watching the light play on skin glowing a now-familiar shade of rose-gold, and wonder if he’s right.
Permanent fix
Jay and Maureen Neitz at the University of Washington in Seattle made headlines in 2009 when they used a virus to deliver genes coding for long-wave photopigments into the retina of male squirrel monkeys. This transformed some of their cone cells, making them sensitive to red-green light and allowing the animals to see in three wavelengths of light instead of two.
A human version of the treatment – a gene therapy for colour blindness – seemed imminent. Yet almost a decade later, the world is still waiting. What happened?
First, the method had to be improved. In monkeys, the virus was injected under the retina, which can be risky. “We never felt this was going to be an acceptable way to treat humans,” says Jay Neitz. Instead the pair wanted to inject the virus into the eyeball, which is much safer.
The technique was licensed to a company now called , and in 2015 it was announced that a cure for colour blindness was two years away. But the firm struggled to perfect the method, and other priorities meant the treatment fell to the back of the agenda, while the technique’s two creators returned to the lab to refine the mechanism.
This determination paid off: the pair have now developed what should be a safe way to deliver the gene in humans, says Jay Neitz. However, untangling who owns the patent to this version of the technique – and is entitled to the millions of dollars that could be made from it – is causing fresh setbacks. For now, the thousands who have expressed an interest in the treatment can only wait and see.
Do you see what I see?
People from many cultures, including Ancient Egyptians and Native Americans, used a single word for both green and blue. Did they see the same colours we do?
Strangely, the answer is probably no. Linguistic experiments suggest that having a name for a colour makes it easier to perceive. The Himba people of Namibia, for example, have a five-colour system that uses the word buru to describe both greens and blues. Tests show that they are better at telling apart similar shades of green than Westerners, but , suggesting that the brain takes longer to tell apart colours that sit in the same category.
This article appeared in print under the headline “True colours”
