Color blindness: causes, symptoms, types and features

Of all the senses, sight is the most developed in humans. Being able to see allows us to perceive the stimuli and events that are present around us, which allows us to analyze and assess the situation immediately and to be able to react to it, even instinctively.

However, we don’t all see it the same way. Through our eyes, we see a lot of things: shapes, depth … even colors. But there are people who cannot detect any of these properties. This is the case with color blindness, Which we will explain what it is and what are its causes.

    The perception of color

    Humans are able to see through a complex association between light-sensitive cells and the neurons that transmit and process this information: the visual system. this system is responsible for capturing images by refraction of light, Through which we can capture the elements of the environment effectively and efficiently. The images are captured by the main organ of vision, the eye, and then processed in the brain.

    When an image is captured, light enters the eye through the cornea and passes through the eye until it reaches the retina, where the image in question is projected inverted.

    In the retina, there is a series of receptors that capture different aspects of the image, cones and sticks. While sticks focus on capturing the level of brightness through their extreme sensitivity to light energy, cones are primarily responsible for providing color information.

    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 (in particular, they contain erythropsin, chloropsin and cyanopsin, which allow you to see red, green and blue respectively).

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

    • You might be interested in: “Colors and emotions: how do they relate to each other?”

    What does it mean to be color blind?

    A person who shows severe difficulty or a complete lack of ability to perceive one or more colors is considered color blind. Also called color blindnessColor blindness means that the eye is not able to pick up the wavelength corresponding to a certain color, either because it does not have the pigments for it, or because it has stopped working.

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

    It is a disease that has so far been chronic, Although gene therapy research in the future may offer some sort of solution to this problem. As a general rule, color blindness is usually not an adjustment problem and usually does not have a major impact.

    However, this condition disables the exercise of certain professions and activities. For example, although they may have a driver’s license, professions such as piloting are prohibited due to the risk of not being able to distinguish certain colors or signs.

    Why does this disorder occur?

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

    The fact that the alteration is on this sex chromosome explains why color blindness is a condition that occurs much more frequently in men. By having only one X chromosome, inheriting a chromosome with the mutation that causes color blindness will eventually develop, whereas in the case of women this only happens if both sex chromosomes have the mutation that causes color blindness. generates color blindness.

    In addition to their genetic origin, there are a few substances that can also be induced as a side effect, Have a few cases of drugs that produce it, such as hydroxychloroquine.

    Finally, certain strokes or diseases such as macular degeneration, dementia or diabetes can cause damage that prevents the perception of color, either through damage to the retina, the optic nerve or areas of the brain where information is processed.

      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 also have varying degrees of difficulty detecting it. they can differ the tones that they will be able to perceive. Here are the most famous types of color blindness.


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

      Sometimes it causes confusion of two colors, as in the example of the confusion between red and green. It should be borne in mind that it is not a question of not seeing a single color, but also of not perceiving correctly all those colors which result from the combination of this one with others.

      Likewise, it is possible that the dichromatism occurs only in one of the eyes, having in the other a vision of the trichromatic color. Depending on the type of receiver that is not working properly, they can be distinguished three subtypes of dichromatism:


      The missing pigment is the one that matches the green. Short wavelengths will be perceived as blue, while from a neutral point where you perceive the color gray, you 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 he reaches a neutral point where he perceives the gray color. From this neutral point, as the wavelength increases, he perceives different shades of yellow.


      Blue pigment is the one that is not working properly in this type of color blindness. This is the less common subtype and usually results in greater loss of perception than the above types. These people perceive the color green in front of short wavelengths, to begin to see red from a neutral point.

      abnormal trichromy

      In this case, the individual possesses all three types of pigments, however at least one is functioning abnormally and cannot perceive color in the same way as a trichrome.

      In this case, they need the intensity of the color to be much higher than usual in order to be able to capture it. It is also common for the colors to be confused. As for dichromatisms, we can find three types:

      • Deuteranomaly: The green pigment is not optimal.
      • protanomaly: Red is not fully perceived by the eye.
      • Tritanomaly: This time, the color that is not captured correctly is the blue.

      Monochromatism or achromatism

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


      One of the most widely used tools for diagnosing color blindness is the Ishihara color test. This tool consists of a series of images created with various very close stitches which, from the different patterns of their coloring, form an image. People suffering from some kind of color blindness find it difficult to see the image that forms, because beyond the color of the dots, nothing gives clues about the shape of this figure.

      However, it should be remembered that the diagnosis can only be made by specialists who examine each individual case.

      Bibliographical references:

      • Adams, AJ; Verdon, WA and Spivey, BE (2013) Vision des couleurs. In: Tasman, W. and Jaeger EA, eds. Duane’s Fundamentals of Clinical Ophthalmology. flight. 2. Philadelphia, PA: Lippincott Williams and Wilkins.
      • Goldstein, EB (2006). Sensation and perception, 6th edition. Debate: Madrid.
      • Wiggs, JL (2014). Molecular genetics of certain eye disorders. A: Yanoff M, Duker JS, eds. Ophthalmology. 4th ed. St. Louis, MO: Elsevier Saunders.

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