Fact Sheet - Colour Blindness   

Colour blindness affects around 8% of males and 0.5% of females and impinges upon the ability to discern different colours.  In the UK alone that’s nearly 3 million people!  Most commonly reds and greens are difficult to identify and may be interpreted by the patient as the same or similar in colour. 


Colour blindness or CVD (colour vision deficiency) is largely a genetic disorder associated with the X chromosome, hence it affects males more than females.  As a genetic disorder it does not increase or decrease through normal life and currently it cannot be treated.  Research suggests that is either caused by faulty light receivers at the back of the eye or perhaps connected to the nerve pathways to the brain.

CVD can also be induced as a secondary issue associated with certain disease or illness e.g. diabetes and multiple sclerosis.  The general ageing of the eye will also reduce colour perception across the whole colour spectrum as the lenses in our eyes tend to lose transparency.  Take a look at some artists work in later life and you will often see much more vivid colours being used, most likely because cataracts are forming in their eyes and dulling or ‘flattening’ their colour perception. 


There are 3 main types of genetic CVD conditions which can vary from mild to severe forms; protanomaly/protanopia, deuteranomaly/deuteranopia and tritanomaly/ tritanopia and these terms relate to the three main colour receptors in the eye.  Protanopia relates to a red deficiency, deuteranopia relates to a green deficiency and tritanopia to a blue deficiency.  The deficiency will affect more than just one colour.



    Normal colour vision                           A form of severe red/green CVD              Tritanopia (severe loss of blue

(Deuteranopia)                           vision)

People with red or green deficiencies will see the world in a similar way to each other because red and green are very close together on the light spectrum. Most people think red/green colour blind people confuse just red and green. This is not the case at all - red/green colour blind people have problems with colours right across the spectrum, particularly reds, greens, oranges, browns and greys, as the images above demonstrate.

Blues and purples can be confused too because of the red tones in purple.


All opticians will have a test available to test for the main 2 types of CVD but not all have the additional test system that covers all three deficiencies.  Colour deficiency testing is no longer routinely undertaken in schools and is not a statutory part of an eye examination in the UK but is something normally offered free as part of the eye test on request.

School and Careers

There are many obvious careers which CVD sufferers cannot embark on including electricians and pilots but most people find ways to manage their lives very successfully.  However, regular issues crop up with daily tasks where the CVD sufferer faces challenges e.g. shopping for fruit and vegetables, clothes selection.

Children with severe CVD are entitled to extra help in school and for exams (e.g. science, geography, ICT, maths) but teachers are generally unaware of the needs of colour blind pupils. Parents of CVD children should therefore ensure the school is aware of their child’s condition, including how to support them correctly.

Parents should also advise their child’s pre-school to avoid loss of confidence in early learning which can arise because pre-school teaching is heavily weighted towards colour perception.



There is no known treatment for CVD.  It is possible to create coloured filters in lenses to try and shift the colours to a slightly different part of the visual spectrum but these need to be incredibly task specific e.g. you might be able to produce a coloured lens to help identify a particular shade of red better but it wouldn’t work on a different red tone.

Want to know more? 

There are many sources of information on the web but our favourite site is; www.colourblindawareness.org .  Here you will find some fantastic visual images demonstrating clearly the issues faced by CVD sufferers along with tips to manage things day to day.



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