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Color blindness: an anomaly of vision

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Color blindness affects nearly 8% of men worldwide. Despite the frequency of this visual disorder, it is still relatively unknown by the majority of French people. Did you know, for example, that there were several types of color blindness? We detail the causes and consequences of this anomaly.

What is color blindness?

Color blindness is a genetic and often hereditary anomaly , due to the dysfunction of the retina , the membrane that lines the back of the eye . When it works properly, the external light enters the eye and stimulates different types of cells, which will then send electrical signals to the brain, to enable it to reconstruct the colors . Among these cells, we find the cones , divided into three types, according to the colors they will recreate: red, green and blue. It is their interactions that allow the brain to capture all the nuances of color. A person with normal three-color vision is called trichromatic .


But in a person with color blindness (about 8% of men and almost no women), all types of cones do not work properly. That's why she can not distinguish all the colors. Most often, the dysfunction comes from green cones, but it can also come from the reds and more rarely from the blues. It is therefore a dichromatic daltonism: the person sees the world in the nuances of the two colors he has left. In some extremely rare cases of deeper color blindness , it is no longer possible to distinguish any color, due to a total dysfunction of the cones. This is called achromatopsia .

What do color-blind people see?

Most of the time, color-blind people have trouble distinguishing shades of green and sometimes red. More rarely, the shades of blue. To get a better idea of a color-blind person's worldview , we advise you to watch the video of the Youtube channel Panthère Bleue on the subject. This anomaly therefore does not represent, a priori, any direct risk to health . Where daltonism can, on the other hand, be complicated to manage, it is in everyday life. It is indeed difficult to drive safely, when we can not distinguish the colors of a traffic light or those of a traffic sign. It can also be a handicap in some professions, such as aviation, medicine, transportation, etc. Color-blind people may also have trouble choosing their clothes, the color of their car or even their glasses.

Daltonism: How to track it

Some forms of color blindness are very difficult to detect, especially the lighter ones, because people are not always aware of it. The most famous and most used test is that of Ishihara , composed of 38 colored plates containing a colored figure. There is also a simplified version of this test, with only 8 boards, more suitable for children.


Other tests have also been designed: Holmgren's , with wool strands on a gray background and Farnsworth's , with pellets of more or less saturated colors. [ =]
Note: this visual disorder is not healing, but can not evolve either. After a positive test, the person with color blindness will have to learn to live with this handicap , especially by developing other referents that will compensate for the non-perception of certain colors.

In addition to this necessary adaptation, people Color-blind people can now turn to certain optical solutions, such as the EnChroma glasses. They compensate for color blindness and allow better perception of colors and contrasts!