Color ametropia

Classification according to ICD-10
H53.5	Color vision disorders
ICD-10 online (WHO version 2019)

Ishihara board, on which normal sighted people can clearly see a green "W" in the style of the Wikipedia logo on a red background.

Under Farbenfehlsichtigkeit (dyschromatopsia, Dyschromasie) refers to a hereditary abnormality of the retina , but only about one percent of women are affected by eight to nine percent of men. Those affected have an abnormality in at least one of the three color-imparting receptors on the cone cells of the retina of the eye . This restriction of color sense, which is harmless for those affected, should not be confused with the very rare color blindness .

The exact type of color ametropia can be determined in humans with a Farnsworth test or with an anomaloscope . A simple qualitative method consists in presenting the test person with a pseudoisochromatic color table according to Ishihara , Stilling -Velhagen , Ernst Heinsius or Edridge-Green. Other special methods ( Beyne Lantern test ) are also used to determine whether the person's eyesight is suitable for certain occupations (pilot) .

A comparatively common color ametropia is red-green poor eyesight .

root cause

In most cases, color ametropia is genetic, i.e. innate. A fully color-capable person has three different receptors for daytime vision , the so-called cones, and is therefore one of the trichromats ( ancient Greek τρίς trís 'three' and χρῶμα chrôma 'color'). The three color receptors convey the basic colors red, green and blue; the mixture of these receptor excitations gives the sensory impression color . For example, the color yellow is created in the brain by stimulating the receptors for red vision and green vision (see basic color ). In the case of color ametropia, the function of at least one of these receptors is restricted. A full functionality of color vision is also referred to as polychromasia in healthy people .

Classification

Monochromatism

Living beings with only one color-transmitting receptor (red, green, blue or UV) are monochromatic (ancient Greek μόνος mónos 'single'). You cannot perceive any differentiable colors, only grayscale.

Dichromacy

Living beings with two types of cones for color perception are called dichromates (ancient Greek δίο dío 'two'). People who have a defective color receptor include:

• Protanopes lack the L-cones (L for long / long-wave light). You have no way of processing the sensory stimuli controlled by the L cones (which are triggered by incident light / photons). Since the light that excites the L-cones is mainly in the red spectral range, we speak of red blindness. If the opsin gene for the red cone is changed by a mutation so that its absorption maximum is too close to the M cone, it is called a protanomaly .
• Deuteranopes lack the M cones (M for medium / medium). These are the cones that mainly respond to light in the green color range. Therefore one speaks of green blindness. If, due to a mutation, the absorption maximum of the green cone is too close to that of the red cone, this is called a deuteranomaly .

The above are collectively referred to as red-green poor eyesight . Protanopes and deuteranopes are referred to as red or green blind. A special case is the blue cone monochromatism , in which red and green blindness is present at the same time.

• Tritanopes lack the S cones (S for short) or (in German) the K cones (K for short). Affected are blue-blind. One speaks of blue-yellow poor eyesight . This is much rarer than red / green poor eyesight.

People with color vision defects are of interest to science because their poor eyesight can be used to verify or falsify theories about vision .

See also

• Color perception
• Cones and chopsticks

literature

• Oliver Sacks : The island of the color blind . From the American by Hainer Kober . Rowohlt, Reinbek 1998, ISBN 3-499-60560-0 .

Web links

• Page with a more detailed description of the color ametropia as well as standard color tables of the colors perceived as the same by those with color defects
• Checking images and web content On this page you can get an impression of how people with ametropia perceive the colors. (English)

Individual evidence

1. ↑ Tables for testing the sense of color: the Stilling-Hertel'schen Tafeln / Ed. By Karl Velhagen Jun [ior]. 21., rework. Output. Thieme, Leipzig 1952.
2. ↑ Heinsius, Ernst: Color vision disorders and their testing in practice: 23 tables. Enke, Stuttgart 1973.
3. ↑ Edridge-Green, F [rederick] W [illiam]: Card test for color blinndness. Bell: London [1927].

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !