WHEN THE RAINBOW VANISHES

Millions suffer from colour vision deficiency, preventing them from seeing the full glory and spectrum of colour. Yet technology is being developed to open the world’s beauty up to them.

Colour vision deficiency, commonly known as colour blindness or CVDs, affects about 200,000 New Zealanders (about 4.5% of the population). CVDs are caused by faulty photopigments; molecules that detect colour in the cone-shaped cells in the retina. The retina typically has three colour cones: blue, green, and red.

The degree to which a person has colour vision deficiency varies from a total loss of colour discrimination through to a very mild loss where they may not be aware they have colour vision deficiency at all. The most common form of CVD is red-green colour blindness, which makes it hard to tell the difference between red and green.

“The cause of the inherited red-green CVD is the genetic information for the two photopigments (red and green) in the cone receptors in the retina that are carried on the X chromosome,” says Emeritus Professor Stephen Dain, School of Optometry and Vision Science at UNSW Sydney. “The information for one may be missing or altered. When it’s missing the person can only see two dimensions of colour rather than three. When it is altered, the person has three dimensions of colour, but one dimension is altered. I often use the analogy of a TV that, instead of red, green and blue primaries, it has red, green and orange. It can still display colours but in a limited range,” he says.

TYPES OF COLOUR BLINDNESS

There are four types of red-green colour vision deficiencies: deuteranomaly (also known as deutan), where the green photopigment is altered (affects 5% of males); protanomaly, where the red photopigment is altered (affects 1% of males); deuteranopia, where the green photopigment is missing (affects 1% of males); and protanopia, where the red photopigment is missing (affects 1% of males).

Blue-yellow colour vision deficiency is much less common (around 1 in 15,000 males and 1 in 45,000 females). The two types of blue-yellow colour blindness are tritanomaly, which makes it hard to tell the difference between blue and green, and between yellow and red; and tritanopia, which makes you unable to tell the difference between blue and green, purple and red, and yellow and pink. Tritanopia also makes colours look less bright.

The inability to see most colours is rare. Known as monochromacy, it is the most severe form of colour blindness and results from all three cone receptors having photopigments that do not work. Thus the world appears in black, white and grey. People affected by monochromacy may find bright light hurts their eyes and suffer from uncontrollable eye movements. “Colour vision deficiencies may be inherited or acquired,” says Emeritus Professor Dain. “Acquired CVDs result from diseases that affect the eye and visual pathways. Inherited CVDs are predictable and consistent, [usually] affect both eyes equally and do not progress. Acquired CVDs are variable and may change.”

Colour vision deficiency may impact people trying to perform certain jobs. Commercial pilots, some seafarers, commissioned officers in the armed forces, and police staff rely heavily on accurate colour vision and colour vision standards may apply. Other jobs that may be impacted on a practical level by CVD include florists,

“I REMEMBER COLOURING IN TREES AND MY MUM HAVING TO HELP ME.” CHRIS VOZZ

painters, graphic designers and chefs. Then of course there is the impact in civilian life: such as not being able to tell when the traffic lights are green or red, or whether meat has been properly cooked.

Chris Vozz, a drummer, composer and sound engineer, has deutan colour blindness. “I discovered I was colour blind when I was in primary school. Colouring trees, my mum would have to help me because I would often colour the trunk green instead of brown. I also had a hard time seeing purple and often got colours confused with each other, mainly greens and reds and blues and purples.”

There are a number of colour blindness glasses and lenses available in New Zealand and Australia. EnChroma have recently released its colour blindness glasses in Australia, also available in NZ from their site. “EnChroma glasses are engineered with special optical filters that help people with red-green colour blindness see an expanded range of colours and to see them more vibrantly, clearly and distinctly,’’ says Erik Ritchie, CEO of EnChroma.

Vozz was recently given EnChroma glasses and was amazed at the transformation: “After wearing the glasses I saw that there were more than three colours in the rainbow,’’ he says. “I could only ever see blue, green and orange before as colours kind of joined together. When I took them off I realised everything looks as if I was looking through a green lens, everything had less vibrance. The most shocking things I’ve seen for the first time are orange leaves in trees, the full rainbow and red and pink are so much brighter.’’

The EnChroma Colour Accessibility Program in Australia enables public venues and organisations, such as museums and schools, to buy or loan the glasses. The Chau Chak Wing Museum at the University of Sydney is the first Australian museum to offer glasses to red-green colour deficient visitors so they can experience the exhibitions in vibrant colour.

MAKING A WORLD OF DIFFERENCE

“We make glasses for both indoor and outdoor use,” says Ritchie. “The indoor glasses are ideal to help colour blind students at school who find it hard or frustrating to understand schoolwork that uses colours. Many people like the outdoor glasses to see colours during hikes in nature, sunsets, visits to gardens, telling teams apart at sports events and for overcoming everyday life obstacles like picking out clothes, or telling if fruits and vegetables are ripe or not.”

Since using the glasses, Vozz has found certain things much easier. “I guess I unknowingly learnt how to navigate certain things, such as traffic lights – green did not look green, but I know that the bottom light which appears white means go, and stop signs are kind of a dirty red/brown,” he says. “[Since using the glasses] they have made shopping easier as I can find items just by looking at the packaging, as they stand out. With my work, creating content and colour grading music videos is so much easier. And rewatching some of my favourite films is like the first time!’’

Emeritus Professor Dain said: “These lenses do introduce some increase in the colour difference in the red-green direction, but this is at the cost of reduced colour difference in the blue-yellow direction. They also introduce a brightness difference. They make greens very much darker so that a red and a green that were indistinguishable to someone are given a brightness difference.”

Hopefully, as the technology addressing colour vision deficiency continues to develop and expand, those impacted, like Chris Vozz and thousands of others, will gain access to a more rainbow-coloured world.