Were you teased about colouring the grass pink when you were a child? Are you slagged about mismatched clothes in adulthood? Have you trouble knowing if meat is rare or well done, or if a banana is overripe? Do you have trouble differentiating between teams on a sports field, depending on what kit they’re wearing?

If so, colour blindness (colour vision deficiency, or CVD) could be the issue.

Linda McGivney Nolan is optometric advisor to Optometry Ireland and comes across colour blindness frequently in her Bray practice.

“Colour blindness generally affects men,” she says. “One in 12 are colour blind [compared to] one in 200 women, but in 30 years practising as an optometrist, I haven’t come across one woman who has the condition.”

These figures mean that, on average, one pupil in every classroom and one person on every sports team in Ireland is likely to have colour vision deficiency, the correct name for colour blindness.

She explains that while the gene for the defect is carried by the female, it is usually only expressed in the male.

“It’s like haemophilia. Say a man is colour blind and has a son and daughter, his son won’t be colour blind but his daughter will carry the gene so his grandsons could end up being colour blind.”

Linda McGivney Nolan is optometric advisor to Optometry Ireland.

Different forms

But how are those with colour vision deficiency affected exactly?

“There are different forms of it, but one of the most common is not being able to tell the colours red and green apart,” says Linda.

“They are seen differently because of an abnormality in the retina at the back of the eye. In the case of colour vision deficiency, some of the cones – the little cells at the back of the eye that pick up colour vision – are missing, or don’t respond to light correctly. Very often this means red and green but it can be to different degrees.”

The cones in the retina contain three photosensitive (light sensitive) pigments: red, green and blue.

She points out there is also a very rare blue/yellow form of colour blindness and acquired colour blindness, which can occur if you have damage done to the retina.This can happen if a person has eye conditions like macular degeneration or glaucoma.

“Sometimes inflammation of the nerve at the back of the eye can mean that red is perceived differently too,” she says, “as pinky and washed out. Certain drugs can affect the cells in the retina also but in those situations colour perception might only affect one eye.”


So how is colour blindness diagnosed? The most common way of establishing whether or not a person has colour blindness is via the Ishihara test.

“In a test like this, you might have a certain shade of background with a number in it. Those who are colour blind won’t see that number because they can’t tell the colours apart. It is the most commonly used, but there are a host of other ones too, like the City University Test.”

If Linda is testing young children’s eyesight and they don’t know their numbers or letters yet, she uses another test called ‘Colour Test Made Easy’.

“It works on the same principles,” she says. “It has shapes printed in a different colour background and a child who is colour blind won’t be able to see that difference between the two, so they won’t be able to make out the shape.”

Colour blindness is usually – but not always – discovered in childhood, she adds.

“Sometimes people would know it is in the family as it’s a genetic condition. A mother might know and look out for it. Some children find out by doing some of the colour blindness tests on TikTok, for a joke in school, or it would come up when they are having an eye test.”

Affects career choice

Discovering that you have colour blindness can be very upsetting, on occasion, if you have your heart set on a particular career.

“I test all the kids in my clinic for colour vision because it does affect your career choice,” Linda says. “One of the saddest cases I’ve come across was when I tested a young guy who was doing his Leaving Cert. He had applied to become an aircraft engineer – a career you need colour vision for as it’s an electrical type of career. Being colour blind, it wasn’t going to be a runner for him. It was awful. He went really pale and quiet when I told him. I felt terrible for him.”

Any career that involves colour perception (ie the interpretation of colour as part of their work, such as design or interpreting signals or anything electrical where wires are colour coded), she states, is out of the question.

“Many of the careers are currently male-dominated. Being in the army or navy, being a pilot, an air traffic controller, a train driver – all require normal colour vision for safety reasons. Working in the food, fashion, textile or paint industries would also be very difficult, and being a Garda or mechanic also requires normal colour vision.

“I was testing a lad the other day who was a panel beater and sprayer, for example,” Linda adds. “He works with 25,000 different colour hues, so he has to have pretty good colour perception. It can be very important in some jobs.”

So what can be done, if anything? There is no treatment available for this genetic condition at present, but there are special glasses or filters called ChromaGen Lenses for Colour Deficiency.

“The lens tints enable people with mild levels of colour deficiency to pass extremely sensitive tests, such as the Ishihara test, and can help those with more severe colour deficiency to pass occupational tests that they would otherwise fail,” Linda says.

“They don’t suddenly fix your colour [perception], but they increase the contrast between the two colours so it makes it easier to differentiate between the two. You won’t pass a colour test with them, however.”

So why buy them then? “Well, you might feel that you just want to have a better perception of colour, and I know in Solas (formerly FÁS), there are certain situations where they will allow the colour glasses to be used — but it’s very much on a case-by-case basis.”

Daily challenges

With colour an important part of everyday life, making decisions around it can be a frustrating experience for those with colour vision deficiencies.

Cooking a meal, grocery shopping, reading maps and colour-related tasks at work are just a few examples of daily challenges a colour blind person can experience. Choosing outfits to wear can also be a problem.

“On a daily basis, matching up clothes can be difficult with some men who are colour blind; keeping their wardrobe very simple,” Linda says.

“They may opt for black, navy, white or grey clothes for fear of putting odd colours together.”

For children or teenagers who are affected, the good news is that books, maps and graphs for geography and science classes are now being designed using a more appropriate choice of colours, so that those who have colour vision deficiency are not disadvantaged.

In sporting circles there is more awareness, also. World Rugby introduced a rule in 2023, for example, that prevented red and green kit clashes during the World Cup in order to help fans, players and referees.

New development

In University College Cork (UCC), students and staff with colour blindness have been given access to glasses that can help with learning material or work in which colours are involved.

This is because of UCC’s partnership with EnChroma, a Californian creator of glasses specific to colour blindness.

The EnChroma glasses have special optical filters that can make an expanded range of colours more vibrant, clear and distinct, making colourful information easier to understand.

• To see how a person with each of three different types of colour blindness sees a pack of colouring pencils compared to someone with normal colour vision, visit the support organisation’s website colourblindawareness.org Advice for teachers of colour blind students is also available there.

• Ishihara tests can be viewed at colorlitelesn.com/ishihara-test.html

Did you know?

• Driving isn’t usually an issue for those who are colour blind.

• It isn’t a problem because they can see from the brightness of the traffic lights which one is on.

• They know that the top one means stop even though they don’t see it as the bright red colour that other people see it as.

• For more information about support for those with colour blindness, https://www.fightingblindness.ie/

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