What is colour vision deficiency (colour blindness)?

Medically reviewed by Tina Patel, Contact Lens Optician at Feel Good Contacts.

What is colour blindness?

The formal term for colour blindness is 'colour vision deficiency'. Those with colour vision deficiency (CVD) cannot perceive colours in the way most people do. Our eyes use three types of cone cells affected by light sensitivity; these cells help us to recognise colour. When people cannot see colours accurately it is because they are missing one of these cone cells. The missing cone cell results in an inability to see a section of the light spectrum, affecting colour perception.

light spectrum affecting colour vision

Perceiving colours incorrectly can impact daily life in many ways, from not being able to tell if your banana is ripe, to not seeing that your skin is sunburnt. Traffic lights are not usually a problem because although the red light and green light may not be visible, the brightness of the light can be a guide, along with common knowledge that red is at the top, amber is in the middle and green is at the bottom.

Types of colour blindness

Some common types of colour blindness include:

  • Protanopia- people with protanopia cannot recognise the colour red due to the absence of red cones. Such people will see red as darker than usual and are likely to confuse reds, yellows and greens.
    Protanomaly – in this condition, the red cones do not detect enough red and causes those affected to get confused by shades of the same colour from the red-green-yellow spectrum, such as perceiving red as green.
  • Deuteranopia- people suffering from this condition cannot differentiate between red and green pigment. This type of colour blindness causes confusion between reds, yellows and greens with the hues tending to shift towards the red end of the colour spectrum.
    Deuteranomaly- this type of colour blindness makes the green look more red and causes those affected to have a reduced sensitivity to green light and confuse shades of the same colour from the red-green-yellow spectrum.
  • Tritanopia is when the blue cones are missing, people are unable to tell the difference between blue and yellow. This is the least common type of colour blindness.
    Tritanomaly - people suffering from this condition will find it hard to tell the difference between blue and green, and yellow and red.
  • Achromatopsia or monochromacy - when people cannot perceive any colours. People with this condition see the world in black and white.

Types of colour blindness

Diagnosis of colour blindness

Colour blindness can be diagnosed using colour vision tests such as the Ishihara test and the colour arrangement test. During an eye test your optometrist should test your colour vision as a matter of routine, but not all opticians in the UK do this test routinely you may have to request a colour vision test specifically and sometimes even pay for this as an addition to your test.

The Ishihara test will require the participant to read the numbers on an image made up of coloured dots.

The colour arrangement test comes in various forms which involve matching or arranging coloured objects according to their shades.

It’s important to have regular eye tests, if you haven’t had one in the last two years, you should book one today!

What is it like to have colour blindness?

People experience colour deficiency in varying levels of severity. Some people can see colours fairly well as long as they are well lit, and struggle to see colours in darker surroundings. Some people have difficulty distinguishing between colours in good or bad light. A small number of people cannot perceive colours at all and see the world in a grey tint, but they are rare cases.

Is there a cure for colour blindness?

Currently, there is no cure for colour blindness. There is, however, emerging evidence to show dyed contact lenses could help with symptoms of colour vision deficiency. Researchers at the University of Birmingham have developed a dyed contact lens that could help people see colours more efficiently. The people who tested these dyed lenses reported an improved ability to distinguish between colours.

The dye is completely safe to use and is also inexpensive. The dye could also be used in contact lenses as well as glasses. Although there are already sunglasses to help with colour perception.

How common is colour blindness?

Colour blindness affects 1 in 12 men and 1 in 200 women worldwide. In Britain alone, there are 3 million people who have colour vision deficiency with the majority being male.

Is colour blindness genetic?

Colour blindness is largely hereditary, however, it can also develop from illness, medication, eye-related accidents and eye conditions such as age related macular degeneration. The condition is passed from parent to child via the X chromosome, which is why it largely affects men much more so than women.

A deficiency in seeing colours can be experienced later in life, however, once experienced the severity of the blindness usually remains the same. If you are colour blind and notice a change in the way you perceive colours, contact your optician.

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