How to get tested for colour vision deficiency, why it occurs, what problems it may cause and how to manage it.
Have you or your child been diagnosed as colour blind? Colour vision deficiency (most commonly known as colour blindness) is usually genetic, meaning it’s likely to run in your family.
While it makes it difficult to identify or distinguish between colours, colour blindness is rarely a sign of anything serious, and for the most part it causes minimal disruption to a person’s life.
We speak to Dr Clare O’Donnell, trained optometrist and head of research division at specialist eye hospital group Optegra about why people experience colour blindness and the future implications:
What is normal vision?
In order to understand deficiencies in colour vision, it’s helpful to understand the way in which colour is normally perceived.
Light passes through the cornea (the clear window at the front of the eye), the lens and the vitreous (the jelly of the eye), and is then focused on the retina. The retina is the film on which the image is projected. Within the retina are photoreceptor cells that detect light. The photoreceptor cells convert light into nerve pulses, which are processed by other nerve cells within the retina before being transmitted to the brain, via the optic nerve.
Most people affected by colour blindness are probably better described as having a deficiency of their colour vision
There are two types of photoreceptors in the retina: rods and cones. Rods are sensitive only to dim light and do not contribute to colour vision. Cones, on the other hand, are used for high-resolution colour vision. There are three types of cones: red, green and blue. In the same way that all the colours on a television screen are made by a combination of red, green and blue, all the colours that the eye perceives are made by the differing stimulation of these red, green and blue cones.
What is colour blindness?
Inherited colour vision deficiency, commonly known as ‘colour blindness’ affects eight per cent of the male population, but only 0.4 per cent of females. This male/ female disparity is because the genes coding for red and green cone pigments are located on the X-chromosome.
Inherited colour blindness affects eight per cent of the male population, but only 0.4 per cent of females.
‘Although we tend to talk about colour “blindness”, which suggests total inability to see colour, colour blindness is actually rare,’ says Dr O’Donnell. ‘Most people affected are probably better described as having a deficiency of their colour vision.
‘Colour deficient people still see colours, but they might look different to how others see them, certain colours are hard to tell apart or they can appear dull,’ she adds. ‘There are two main types of colour vision deficiency – red-green and blue-yellow – and it can range from being quite mild to more severe.’
How is colour blindness diagnosed?
Colour blindness is diagnosed using a colour vision check. ‘This can be done at the opticians as part of a routine eye test,’ explains Dr O’Donnell. ‘There are a number of different tests available, but the most commonly used test involves looking at a series of pages with coloured dot symbols against a background of coloured dots.’
‘People with red-green colour vision deficiency tend to see these symbols differently and sometimes the symbols blend into the background, making them invisible,’ adds Dr O’Donnell. ‘Other tests are sometimes needed, to provide more detailed information. These could involve arranging coloured samples and some employers might ask for a test that involves identifying coloured lights, if coloured signal recognition is critical for that occupation for example, train drivers.’
How can you support your colour blind child?
Dr O’Donnell suggests the following ways to help and support your child:
✔️ If they have not had an eye test, arrange an appointment with your optician.
✔️ Be aware that your child might be self-conscious, so offer reassurance and don’t make a big deal of it – it really won’t affect their ability to lead a full and active life!
✔️ Explain that colour vision deficiency is common – it affects around one in 12 boys (it’s more unusual in girls).
✔️ Tell them we usually inherit colour vision deficiency from our parents and it usually affects both eyes.
✔️ In rare cases, it can be a sign of other eye issues, so a check-up with your optician is always a good idea.
✔️ Most children with colour blindness can see things quite clearly, it’s just that they will have more difficulty distinguishing between certain colours and in some cases colours appear quite dull.
✔️ Telling your child’s teacher at school is a good idea, so they are aware not to put the child on the spot by asking them questions that require good colour discrimination, not writing with pale colours on whiteboards and not setting tasks that rely on colour only. It is usually easy to make use of other indicators, eg labelling objects like coloured pencils with stickers with the name of the colour written on them.
What are the implications of colour blindness?
The good news is that, in most cases, colour blindness will not get worse over time and will not impact your ability to live a full and active life.
‘While there are a small number of occupations where colour blindness could have serious safety or cost implications, and are therefore not suited to people with colour vision deficiency, in most situations people simply adapt to it and learn to put coping strategies in place to make up for any difficulties they have distinguishing certain colours,’ says Dr O’Donnell.
In most cases, colour blindness will not get worse over time or impact on your ability to live a normal life.
‘This might involve asking a family member to help when choosing clothing, checking whether fruit is ripe or food is cooked properly, or asking a colleague in the workplace to double check tasks in situations where colour mix-ups could cause problems,’ she adds.
‘If you have a red type colour vision deficiency, it is good to be aware that red lights can appear duller and, practically, this might mean driving in very poor conditions can be more challenging. For example, in thick fog, the brake or fog lights on the car in front might be harder to see.’
💡 If you have colour blindness, future jobs may also be slightly limited: certain careers, which require accurate colour recognition, such as pilots, electricians or train drivers, will not be suitable.
Colour changes later in life
If you notice you are starting to see colours differently later in life, it’s important to visit your optometrist. ‘Some eye or health conditions that might develop later in life can also cause colour vision problems, so any changes to your colour vision should be checked out by having an eye examination,’ says Dr O’Donnell.
‘Colour vision problems that are acquired later in life could be due to problems such as glaucoma, diabetes, retinitis pigmentosa and other conditions affecting the nerve at the back of the eye – the “optic neuritis”. Having this checked out might mean the problem gets treated sooner rather than later.’