What Is Colour Deficiency?

16 September 2019

Author: Jacci

What Is Colour Deficiency?

Many believe that the term 'colour vision deficiency' would mean you were colour blind, but this is often used in the wrong context and can be incorrect. Colour deficiency is the condition where your ability to distinguish colours and shades is below average.

How Colour Vision Works

Within the retina of our eyes lies two types of photoreceptors (cells that respond to light) called rods and cones, both work together to pass information to the brain. There are around 120 million rods which only process the light, and between 6 to 7 million cones that process colour. These millions of cones are gathered together tightly in the center of the retina.

Each cone carries one of three photopigments which are:

  • S-cones: reacts to short-wavelength light (blue)
  • M-cones: reacts to medium wavelength light, (green)
  • L-cones: reacts to long-wavelength light, (red)

These work together to mix information and create the colours we see if we have normal colour vision. If you are someone who suffers from a colour deficiency, however, this may not be the case.  

colour deficiency in eyes

There are mainly three categories of Colour Vision Deficiency:

Protanopes and Deuteranopes- (red/green colour blindness)

Protanopia and Deuteranopia are the most common and also known as "red-green" colour deficiency. The individual will struggle to analyse shades of red, yellow and green.

If you have protanopes colour deficiency it would mean your L-cone is missing or has malfunctioned and would struggle to distinguish red tones.

If you are someone suffering blindness to greens this is known as Deuteranopia. This usually occurs when there is a malfunction of the M-cone or there is none at all. People suffering from this type of colour deficiency will only be able to distinguish 2 to 3 different hues, whereas a person with normal vision can see 7 different hues.


Someone with “red-green” colour deficiency:

  • confuses shades of reds with black
  • may struggle to tell the difference between reds, oranges, yellows, browns and greens
  • colours will appear much duller 
  • can have trouble distinguishing shades of purple

Men are at a higher risk of being diagnosed, as it affects around 1 in 12 of males and 1 in 200 of females.



Tritanopia is more uncommon. People with this condition find blues, greens and yellows hardest to identify. This is a result due to the S-cone failing to process colour information to the brain. Light blues will appear as greys, dark purples seem blacker, and mid-greens will present itself as blues and oranges with reds. Tritanopes can also be known as "blue-yellow" colour vision deficiency.


How to Test Your Colour Vision

It is crucial to attend your two-year check-up with your optometrist as this is the type of condition that can be detected, as well hundreds of other eye diseases and conditions. There are mainly two types of tests performed to distinguish colour deficiency which are:

  • the Ishihara test, this involves identifying numbers contained within images made up of different coloured dots, the most popular out of the two
  • colour arrangement; where you organise objects in order of their different shades of colour


Colour Deficiency Causes

In most cases, colour vision deficiency is genetic and occurs when a parent has passed it down to the child. Colour deficiency can also occur later in life due to:

  • eye becoming exposed to harmful chemicals, such as carbon disulphide
  • side effects to certain medication like digoxin, ethambutol, chloroquine, and hydroxychloroquine
  • health disabilities and diseases such as diabetes, glaucoma, age-related macular degeneration and multiple sclerosis

colour vision deficiency 

Top 5 Struggles When Living With a Colour Deficiency

  • Difficulty in learning as colours are used to help individuals with process information, especially in schools
  • Eating food, especially meats as colour helps indicate when edible to eat during cooking.
  • Easily consuming the wrong medication if not labeled correctly
  • Risk of analysing signs and warnings incorrect especially when driving
  • Limiting career choices as certain job sectors require complete colour vision such as pilots and train drivers.


Is There a Cure for Colour Deficiency?

Unfortunately, there is yet to be any cure for inherited colour vision deficiency. There are, however, easy tricks to make daily life easier when living with the condition, such as:

  • Special tinted glasses/sunglasses, which aids you to distinguish between certain colours better
  • Alter technology devices to your needs as many now come with colour settings that can adapt to your condition better
  • Seek help in friends and family to colour coordinate items like clothing and home decoration
  • Provide quality lighting in your home to help identify colours better.colour deficiency

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