How can I tell if I’m colour blind or not?

Were you scolded as a child for colouring the sky purple? Does peanut butter look murky green? Do traffic lights turn brown for stop and blue for go? If the answer is yes, you are most likely colour blind. But not all types of colour blindness are the same. Here is a brief guide to what colour blindness is, what the signs are that you have it and whether it can be cured.

What is colour blindness and how is it caused?

Colour blindness is an impairment caused by a genetic mutation on the X chromosome, passed to children via their mothers who are the carrier for the mutated gene. With this mutation, the light sensitive cells at the back of the eye fail to respond normally to different wavelengths of light that allow those with full colour vision to see different colours.

Many colour blind people are unable to see the colour purple (Image: Archant)

Generally, colour blindness causes the world to appear duller. Owner of EYES on St Albans opticians practice, Jez Levy explains: “Most of us who are not colour blind see approximately one million colours and shades of colour, whereas someone with colour blindness sees between ten and 20 per cent of these colours.”

The most common type involves seeing reduced red or green. This is known as red and green colour vision deficiency, or protan and deutan colour blindness (protanomaly and deuteranomaly). It causes yellows, oranges and browns to all appear similar. If you have this type, you might stop at the traffic lights when they turn brown and see peanut butter as green. You were also probably that child drawing pictures of the sky in purple, because you can’t distinguish purple from blue.

A rarer type, known as tritan deficiency (tritanomaly), means you cannot see as much blue, and sometimes also yellow. People who are blue green colour blind will have problems seeing blues, greens, yellows, pinks and reds. In the rarest of cases, colour blindness can prevent you from seeing colours all together, meaning that the entire world is viewed in greyscale. This type is known as monochromacy.

How is colour blindness checked?

The most reliable way to check if you are colour blind is to visit a specialist and do a colour blindness test. At EYES on St Albans, Jez offers The EnChroma vision test, which can be done either online or on the EYES on St Albans APP and takes up to five minutes to complete.

“The test on the APP throws up various screens of coloured, dotted numbers in different coloured, dotted backgrounds,” explains Jez.

“If you see the number, you hit that number as displayed in the numerical on-screen keyboard. If you are unsure or do not see the number, you simply hit the ‘Pass’ button.”

Once you have completed the test, you learn whether you have colour blindness and if so, the type you have. It also predicts whether special EnChroma glasses could help. These are sold at EYES on St Albans, who are the sole EnChroma retailer within the UK. Using technology recently discovered in America, these colour blind corrective glasses are not a cure and don’t work for all, but they do act as a treatment, reducing problems for many with the impairment.

“The science behind the EnChroma lenses is quite revolutionary,” says Jez. “By blocking out light between the medium and long wavelengths of visible light, colours are enhanced and separated.

“In most cases, when you put on the glasses, the world appears more vibrant and varied. It is like someone has shifted the saturation up a notch. The grass is greener, tomatoes are redder, and finally you can tell the difference between purple and blue crayons.”

EnChroma glasses are available with six different lenses for the various forms of colour blindness and require that you take a test to know exactly which lenses will be most effective for you. For those who are long or short-sighted, they are available in single vision and varifocal prescriptions as well as non-prescription versions.

“We encourage the individual to try on and compare the other densities of lenses,” says Jez. “We also discuss how and when the individual will use these, which also determines which lens design is most suited for the needs of the individual.

“We also offer bespoke designs. Given that everybody’s taste in glasses is different, it is equally as important to get the frame design right for each and every person.”

For more information, visit eyesonstalbans.com or call 01727 838003

Find them at 63 The Quadrant, St Albans AL4 9RD