Color blindness: picture test for red-green weakness & Co.

Color blindness: picture test for red-green weakness & Co.

Colour vision deficiency, or colour blindness, often referred to in general terms, encompasses a spectrum of different colour perception disorders. The so-called red-green colour blindness is the most common. In 2018, around ten per cent of men and 0.4 per cent of women were affected in Germany. With the help of our photo series, you can test whether you, too, have a form of colour blindness. We also tell you what types of colour blindness there are, how they develop and how someone with colour blindness perceives their surroundings.

This is how the test works:  Sit about 75 centimetres in front of your screen and direct your eyes to the centre of the screen. Dimmed room lighting helps to avoid reflections on the monitor that could affect the test. The test uses so-called Ishihara colour charts (named after their Japanese inventor, Shinobu Ishihara). If you can’t see anything quickly in the pictures, you will find the resolution in the description.

Test image 1

Resolution: You recognize the “7 with an intact colour vision”. If you are red-green blind, you will only see a “5”.

What types of colour vision deficiency are there?

There are different types of colour vision disorders. Red-green blindness is also known as dichromas. The cones, which are responsible for colour perception in the eyes, are missing. It lacks either the M cones, which respond to light in the red colour spectrum (red blindness or protanopia), or the L cones, which react to light in the green colour spectrum (green blindness or deuteranopia). The two colours can, therefore, not be seen, depending on how affected they are.

If the cones’ functions are limited, red or green can only be perceived as weaker or differentiated more poorly, which is defined as red-green weakness. In general usage, the terms red-green blindness or red-green weakness are often used synonymously. 

Test image 2

Resolution: In the left circle, visually healthy people can see lines in different colours. If you have a red-green colour blindness, the picture shows a “45”. The image on the right is grey for both colour-blind and colour-blind people.

Complete color blindness

In the case of achromatopsia or achromasia, no colours are perceived at all but only contrasts. It can be hereditary and present since birth, or it can be triggered later in life by a disease such as a stroke or traumatic brain injury.

Test image 3

Resolution: If you have an intact colour vision, you will recognize the “9”. The majority of colour-blind people cannot see the number.

Tritanopia

The so-called K-cones are missing in colour blindness, known as tritanopia. These react to light in the blue spectral range. Those affected have blue blindness or blue-yellow weakness. This colour blindness is relatively rare.

Test image 4

Resolution:  If you have an intact colour vision, you will recognize the “13”. If you only see the “1”, you have red colour blindness (protanopia). If you only remember the “1” and the “3” weakly, you have a mild form of red colour blindness (protanomaly). However, if you only see the “3”, you have green colour blindness (deuteranopia). In the mild form (deuteranomaly), you can see the “3” but only weakly the “1”.

Test image 5

Resolution:  If you have an intact colour vision, you will see a “9”. If you can only see grey dots, you should have your doctor test your colour vision.

Causes of red-green weakness

A genetic defect on the X chromosome causes red-green blindness. This defective gene is inherited recessively – this means that the defect does not appear when there is a healthy gene that is, so to speak, taking hold. Red-green blindness is less common in women because they have two X chromosomes, one of which usually has no colour vision disorder. It can thus compensate for the genetic defect on the other X chromosome. Since red-green colour blindness is always hereditary, it has existed since birth and does not worsen over time.

Test picture 6

Resolution:  If you have colour vision, you can see an orange snake in the image above. In the case of red-green weakness, you will also see a grey line that is green-blue. If you are entirely colour-blind, you cannot see lines.

How is red-green colour blindness detected?

Colour blindness is often not recognized for a long time. The person concerned is initially not aware of his erroneous perception. The social environment then often notices the insecurities of the person concerned about colour perception. For example, when a child draws trees with brown instead of green leaves and green trunks, the colours of a traffic light are not recognized. Additional tests, such as the Ishihara colour chart, can confirm the suspicion. If in doubt, a visit to the ophthalmologist will provide certainty.

Test picture 7

Resolution: You will see a “74” here if you have intact colour vision. Only a “21” can be recognized with an existing red-green weakness. If you only see grey dots, your colour perception is disturbed and should be examined by a doctor.

How is colour blindness tested?

Ishihara or Stilling-Velhagen colour charts are often used to test red-green weakness, as they are also used in this series of photos.

Simple motifs like numbers or lines are composed of differently coloured dots. People with red-green colour blindness can either perceive no images at all or different images than people with intact colour vision. 

Test image 8

Resolution: If your colour vision is intact, you will see a green line on the image. If you have a red-green weakness, you will also see a grey line that is red. If you are entirely colour-blind, you will not see any lines.

Farnsworth-Test

One method of testing for complete colour blindness (achromatopsia) is the so-called Farnsworth test. In this test, the test subjects have to arrange different colour tiles numbered on the back in the correct order on a given colour wheel. 

Test image 9

Resolution: You will see an “8” here if you have intact colour vision. If you only recognize grey dots, you have a disturbed colour perception that a doctor should examine.

Anomaloskop

An anomaloscope is often used to test for red-green weakness in aptitude tests, for example for pilots, bus drivers or police officers. It consists of a circle divided into mixed and comparison fields. The subject looks at this circle through an eyepiece, i.e. a lens similar to a microscope. The divided circle has different colours. The test person has to mix red and green with the help of rotary wheels so that the yellow tint of the mixture corresponds to that in the comparison field. This shows whether a person affected only recognizes the intensity of the colour tones or the colours themselves.

Test image 10

Resolution:  Even with a red-green weakness, you should be able to see this orange line. If you don’t see a line, you should make an appointment with your doctor.

Glasses should help with red-green weakness.

Special glasses have been available for years to help people with red-green colour blindness compensate for their colour vision deficiency. This is possible because the glasses’ lenses filter out parts of the green and red light spectrum. The parts affected are those that people with red-green colour blindness perceive as very similar. This creates a more significant difference between red and green in perception.

An improvement can only be achieved with such glasses if the function of the cones for red and green is still limited in the person affected. If you are entirely red or green blind, the glasses will have no effect.

Test picture 11

You’ll see a green “N” if your colour vision is fine. If you only recognize grey dots, you have a disturbed colour perception, which the doctor must clarify.

How colour-blind people see the world

How do people with colour blindness see the world? The image shown here illustrates how people affected by red blindness (protanopia), green blindness (deuteranopia) or blue blindness (tritanopia) see their environment in comparison to normal colour perception.

 

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