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Color blindness: causes, symptoms, types and characteristics

Color blindness: causes, symptoms, types and characteristics

November 20, 2022

Of all the senses, the view is the most developed in the human being. Being able to see allows us to perceive the stimuli and events that are present around us, and this allows us to analyze and evaluate the situation immediately and be able to react to it, even instinctively.

However, we do not all see it in the same way. Through our eyes we see many things: shapes, depth ... even color. But there are people who are not able to detect any of these properties. It is the case of color blindness , which we will explain what it is and what are its causes.

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The perception of color

The human being is able to see thanks to a complex association between light sensitive cells and neurons that transmit and process this information: the visual system. This system is responsible for capturing images through the refraction of light , thanks to which we can capture the elements of the environment in an efficient and effective way. The images are captured by the main organ of vision, the eye, to be later processed at the brain level.

At the moment of capturing an image, light enters the eye through the cornea and crosses the eye until it reaches the retina, in which the image in question is projected inverted.

In the retina there is a series of receivers that allow to capture different aspects of the image, the cones and the canes . While the canes focus on capturing the level of brightness thanks to their extreme sensitivity to light energy, the cones are the main responsible for providing information regarding color.

Located in the fovea, the cones allow us to capture the color thanks to the existence of three pigments inside , which can capture different wavelengths (specifically they contain erythropsin, chloropsin and cyanopsin, which allow to see red, green and blue respectively).

From the retina, the information will be sent to the brain through the optic nerve, to be processed later. Thanks to this we can be able to recognize a large number of different colors, possessing a trichromatic vision. But What happens in the case of a color blind?

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What does it mean to be color blind?

It is considered color blind to that person who shows a severe difficulty or a total absence of the ability to perceive one or more colors. Also called color blindness , color blindness assumes that the eye is not able to capture the wavelength corresponding to a particular color, either because the pigments are not available for it or because they have stopped working correctly.

This causes that, before stimuli that people who enjoy three pigments in their cones see a certain color, the colorblind subject will perceive a different color and will even be unable to perceive the differences between that color and the one that confuses it (for example, you will see green something that the rest sees of the same color, but also what another non-colorblind person would see red).

It is a condition that has been chronic until now , although research in gene therapy may eventually offer some kind of solution to this problem. As a general rule, color blindness is not usually a problem of adaptation and usually does not have great repercussions.

However, this condition disables for the realization of certain professions and activities. For example, although they may have a driving license, professions such as pilot's are vetoed because of the risk of not being able to distinguish certain colors or signs.

Why does this disorder occur?

The causes of this deficiency in the perception of color are found in the absence of certain pigments in the cones of the retina. This absence has in most cases genetic origin, being caused specifically by Alterations linked to the X chromosome .

The fact that the alteration is in this sexual chromosome explains why color blindness is a condition that appears with much more frequency in males. Having these only one X chromosome, to inherit a chromosome with the mutation that causes the color blindness will eventually develop, while in the case of women this only happens in the case that both sex chromosomes have the mutation that generates the color blindness.

In addition to its genetic origin, there are some substances that can also induce it as a side effect , there are some cases of drugs that produce it, such as hydroxychloroquine.

Finally, some cerebrovascular accidents or diseases such as macular degeneration, dementia or diabetes can cause damage that prevents the perception of color, either by an affectation of the retina, the optic nerve or the brain regions in which the information is processed. of color

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Types of color blindness

As we have seen, color blindness is defined as the absence or difficulty of perceiving the color of objects. However, people with this problem may have different degrees of difficulty in their detection, as well as can differ the tonalities that they will be able to perceive . Below we expose the most known types of color blindness.


The most common type of color blindness is the one produced by the absence of one of the three pigments . Given the impossibility that the pigment in question captures the color, it will be captured through a different wavelength, perceiving another color.

Sometimes this causes two colors to be confused, as in the example of the confusion between red and green . It must be borne in mind that it is not a question of not seeing only one color, but that all the colors that result from the combination of this with others are not perceived correctly.

Likewise, it is possible that the dichromatism only occurs in one of the eyes, having in the other a vision of the trichromatic color. Depending on the type of receiver that does not work properly, you can distinguish three subtypes of dichromatism :


The missing pigment is the one that corresponds to the green . Short wavelengths will be perceived as blue, while from a neutral point where you perceive the gray color will begin to perceive different shades of yellow.


The color that is not perceived is this time the red . The subject perceives the short wavelengths as blue, until reaching a neutral point where he perceives the gray color. From this neutral point, as the wavelength increases, different shades of yellow are perceived.


The blue pigment is the one that works incorrectly in this type of color blindness. It is the less usual subtype and usually causes a greater perceptive loss compared to the previous types. These people perceive the green color before short wavelengths, so from a neutral point start to see red.

Abnormal trichromatism

In this case, the individual has all three types of pigments, but at least one works abnormally and can not perceive color in the same way as a trichromatic.

In this case they require that the intensity of the color be much higher than usual to be able to capture it. It is also common to confuse colors. As with dicromatisms, we can find three types:

  • Deuteranomaly : The green pigment does not work correctly.
  • Protanomaly : red is not perceived in its entirety by the eye.
  • Tritanomaly : this time the color that is not captured correctly is blue.

Monochromatism or Achromatism

People with this strange condition do not have functional cones, unable to perceive color. They can only experience reality in different shades of white, black and gray , basing the totality of his vision on the light detection capacity of the rods.


One of the most used tools to diagnose color blindness is the color test of Ishihara . This tool consists of a series of images created with several very close points that, from the different patterns of their coloration, form an image. People with some type of color blindness have difficulty seeing the image that is formed, since beyond the color of the points there is nothing that gives clues about the shape of that figure.

However, we must remember that the diagnosis can only be made by specialists who examine each case in particular.

Bibliographic references:

  • Adams, A.J .; Verdon, W.A. & Spivey, B.E. (2013) Color vision. In: Tasman, W. & Jaeger EA, eds. Duane's Foundations of Clinical Ophthalmology. vol. 2. Philadelphia, PA: Lippincott Williams & Wilkins.
  • Goldstein, E.B. (2006). Sensation and perception, 6th edition. Debate: Madrid.
  • Wiggs, J.L. (2014). Molecular genetics of selected ocular disorders. In: Yanoff M, Duker JS, eds. Ophthalmology. 4th ed. St. Louis, MO: Elsevier Saunders.

What Causes Color Blindness? (November 2022).

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