Colour blindness

This is a disorder of the colour vision of the human eye. Colour blindness is caused by disfunction of the cells of the retina. It only affects a small percentage of the population and is more common in men than in women. 

Most commonly the problem is the inability to distinguish red, green or blue-purple colours. Colour blindness to do with yellow and blue colours also exists but is less common. Rarely, (less than 1% of affected patients) colour blindness affecting all colours is recorded – in these cases the patients only see se in different shades of grey. Usually, it is a disfunction that is congenial, in fewer number of cases it is acquired. There is no cure for congenial colour blindness, but it is possible to adjust it to a certain extent through optical aids. 

Congenial colour blindness is divided according to the degree of the disfunction in colour vision as follows:

• Anomalous trichromacy – reduced perception of one of the basic colours where all 3 types of cones are present in the eye, but one type is dysfunctional.
• Dichromacy – one of the basic three colours is not recognised and there are only two functional types of cones in the retina – this is the most common type of colour blindness.
• Monochromacy – the eye does not recognise any colours and the patient is unable to see in colour – this is also referred to as complete colour blindness. Cones in the retina are either damaged or have not developed at all.

At the moment there exists no cure for colour blindness.

Test yourself

Tests designed to discover colour blindness are based on distinguishing colours of numbers. They appear as colourful clusters of smudges that in healthy vision should appear as a concrete symbol. There are several such picture schemes and each one helps to identify a specific dysfunction of colour perception if read wrong. Testing is absolutely inevitable in some jobs, for example in transportation.

Picture 1: If you see number 3 you have a dysfunction of the perception of colour where green and red colour is concerned. A healthy individual sees number 8.
Picture 2: A healthy individual sees number 15. A person suffering from the dysfunction of perception of green and red colour sees number 17.
Picture 3: If everything is alright you should see number 5. If not, then you suffer from the dysfunction of the perception of green and red colour and see number 2. A person who is completely colour blind will not recognise any number.
Picture 4: A healthy eye sees number 73. If you see number 28, see your eye doctor.
Picture 5: This obvious number 12 is seen by both, a healthy as well as a colour-blind person.
Picture 6: If healthy you should see a 74 here, if suffering from a colour perception dysfunction of green and red you will see number 21. A colour-blind person does not see the number at all.