How common is color blindness

Color blindness (Color impairment, Color vision deficiency, Red Green weakness)

The term "color blindness" is often used incorrectly in normal language usage: What is usually meant is a mostly congenital color blindness - mainly red-green weakness - which predominantly affects men.

Short version:

  • People with total color blindness do not perceive any color, they only see black, white and gray tones.
  • Color blindness can only affect individual colors (red / green / blue / yellow).
  • Color vision deficiency is the most common, especially red-green deficiency.
  • Color blindness and color vision deficiencies are usually congenital.
  • Since most cases of color blindness or color vision deficiency are congenital defects, causal therapy is not possible.

Colors are not perceived equally intensely by all people. Any deviation from normal color vision is called a color disorder. It can occur in different forms:

Color blindness

Overall, color blindness is very rare.

At a total color blindness no colors at all, only black, white and gray tones are perceived. In addition, there is usually poor visual acuity and strong sensitivity to glare.

The Color blindness can also only affect individual colors. If a person is red-green-blind, either red or green is not recognized. The two colors cannot be distinguished from each other. In the case of blue blindness, the color blue is not recognized and is confused with yellow.

Color vision deficiency

Color vision deficiency is the most common form of color vision disorder. The color perception is still present to a different extent, but the respective colors are perceived less intensely and can therefore only be differentiated or confused with difficulty or not at all.

Red Green weakness (Daltonism after its discoverer John Dalton)

About 8% of all men are affected by the red-green weakness, with women the proportion is much lower at 0.4%. In common parlance, the red-green weakness is often incorrectly referred to as color blindness.

Red and green weaknesses are summarized under the term red-green weakness, as they have similar effects: instead of red and green, those affected see different shades of gray and brown.

  • Green weakness: Affected people are less able to distinguish the color green from red. Green weakness occurs more often than red weakness.
  • Red weakness: Affected people are less able to distinguish the color red from green.

Blue weakness

Those affected cannot perceive the color blue and confuse it with yellow. Overall, only very few people are affected by blue weakness. It can occur as a secondary disease of macular degeneration.
 

Monochromatism: Affected people only perceive one color; very rare


How is color vision created?

On the retina of the eye there are various sensory cells that make seeing possible in the first place: rods enable light-dark perception, cones enable color recognition. There are three types of cones that respond to different wavelengths of light:

  • Long-wave light: red
  • Medium wave light: green
  • Short-wave light: blue

If the cones are stimulated by the light, they convert this stimulus into electrical impulses. These in turn reach the brain, where the actual color sensation takes place. All other colors in the field of vision are the result of mixtures: if cones located close together determine, for example, that an object is both green and blue, it is recognized as turquoise.

If one or more of these cone types do not function correctly or only to a limited extent, the corresponding colors and the resulting mixed colors will not be perceived correctly (color impairment).

If all cones are inoperable (or not present), the color vision fails completely, those affected only see black, white and gray tones (total color blindness). In the Red, green or blue blindness only the corresponding pins are inoperative (or not available).

Why are color disorders mainly affecting men?

Color vision disorders are in most cases congenital and affect men (8%) more often than women (0.4%). However, they can also occur as a consequence of other diseases - such as diseases of the optic nerve, the retina, or the brain - or as a result of poisoning. Men and women are equally affected (5%).

Inheritance using the example of red-green weakness

The red-green weakness is inherited in a sex-linked manner, i.e. the genes that are responsible for the color impairment are located on the sex chromosome X.

Since men (XY) only have one X chromosome, the genetic defect on it comes into play immediately: Affected men have a red-green weakness from birth.

In women (XX), the defect on one X chromosome is compensated for in most cases by the other, “healthy” X chromosome: They have normal color vision.

A defective gene is not passed on from father to son, as sons always receive the X chromosome from the mother. The daughter, on the other hand, carries the defective gene in her genetic make-up without, however, being affected by it herself, as her second X chromosome compensates for the defect. But there is a 50% chance that she can pass it on to her sons. If the son receives the defective X chromosome from the mother, the color disorder comes into play.

How is color vision disorder diagnosed?

Color vision disorders are often recognized relatively late because those affected do not notice the restriction in color perception themselves. In many cases, it is the parents who notice that their child is wrongly naming colors or confusing them with one another.

The ophthalmologist can use various tests to check whether and what degree of color vision deficiency is present. The most important tests:

  • Ishihara test: The affected person is shown colorful boards on which people with normal vision can recognize numbers, shapes and letters. People with color impairment have trouble recognizing them.
  • Farnsworth test: Stones in different color nuances have to be classified from strong to pale.

Is therapy possible?

Since most cases of color blindness or color vision deficiency are congenital defects, causal therapy is not possible. A deterioration in color perception over the course of life is not to be expected; it usually remains constant. The risk of going blind or developing other eye diseases is also not increased compared to healthy people.

In the case of acquired color vision disorders, color perception can improve if the underlying disease is treated successfully.

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Authors:
Astrid Leitner
Medical review:
Dr. Gabriela Valerie Seer
Editorial editing:
Mag. Julia Wild

Status of medical information:

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