Color blindness: see types, symptoms, diagnosis, causes and more


What is color blindness?

Color blindness, also known as dyschromatopsia or partial color blindness, is a visual disorder characterized by the inability to perceive and distinguish the primary colors (red, yellow and blue), in addition to green. In rarer cases, the total absence of color is present.

The disease, known in 1798, was named after the English chemist John Dalton, who was responsible for the first published study on the anomaly of which he himself was a carrier. Studies carried out since then have determined that the human eye is able to distinguish more than 150 shades of different colors, however, this number decreases to those who are color blind, as they do not differentiate their mixtures.

The cause was an inherited genetic alteration linked to the sex chromosome X, so that it has no cure and affects more men, since they have only one X chromosome, while women have two. Statistics estimate that about 8% of the world’s male population and less than 1% of the female population are carriers of the disorder.

Mechanism of color blindness

The retina is the part of the eye where images are formed and later transmitted to the brain via the optic nerve. In a normal retina, there are two types of light-sensitive cells: cones and rods.

Rods are responsible for night vision and are not sensitive to color differentiation. Cones, on the other hand, have three types: tritan (blue), deuteran (green) and protan (red), responsible for daytime vision and color perception. All existing tones are derived from the combination of these three primary colors, so that the absence or mutation of these receptors will cause the symptoms of color blindness.

Types of color blindness

Divided into three groups, there are seven types of manifestation of the disease. Are they:


A rare type of color blindness that affects the three color receivers. Also called achromatic vision, it restricts color blind people to the distinction of black, white and gray tones, thus occurring only the perception of luminosity, without the presence of colors.


Reduction or total deficiency of one of the color receptors. Dichromacia can also be deficient in two types of receptors and cause the distinction to be made in only one of the colors in general, green or red.

This group of color blindness can present itself in the following ways:


Protanopia is the most common type of color blindness, characterized by the absence of protan receptors , which makes it impossible to identify red tones and their derivatives. The person sees in beige, brown or gray tones, red and green tend to be similar, and the colors appear to be darker than they really are.


Deuteranopia is the absence of deuteran receptors , which makes it impossible to identify green tones. Similar to protanopia, the person also sees in brown tones.


Tritanopia is the most unusual type among dichromatics, characterized by the absence of tritan receptors , which makes it impossible to identify blue and yellow tones. In this case, color blinds see colors in different shades, similar to light pink.

Anomalous trichmacia

Partial reduction of one of the color receptors, where the person sees the colors, but with different contrast and saturation. It can be presented in the following ways:


Protanomalia is the partial deficiency of red receptors. Although it is still possible to distinguish some shades between red and green, protanomaly results in less sensitivity and the darkening of that color and the like. It can generate confusion between red and black.


Deuteranomalia is the partial deficiency of green receptors. It is responsible for most cases of color blindness and results in the difficulty in discriminating green.


Tritanomalia is the partial deficiency of blue receptors, which impairs the identification of colors in the range of blue and yellow.

What causes color blindness?

Chromosomes are long sequences of DNA that contain genes, instructions for the development of cells, tissues and organs of each human being. Based on its structure, the sex of a child is defined in pairs of XX, in the case of women, and XY, in the case of men. Color blindness is an anomaly directly linked to the X chromosome, which makes it a genetic condition, usually inherited by your parents.

Rarely does the disorder affect women, as they have two X chromosomes and, if they receive from one parent with the genetic mutation, the other, which is normal, compensates for the change and does not make her a carrier of the disease. However, the person becomes a carrier of the defective gene and can pass them on to their descendants. When both parents have the damaged color blindness genes, your daughter will also have the anomaly. In men, however, receiving a damaged X chromosome is enough to make you colorblind.

In rare cases, color blindness is a defect acquired over the years and not a genetic inheritance, so it can regress or stabilize as long as the cause is properly treated. Other factors can also damage the cells of the retina, causing visual color impairment, such as:


Color blindness can be a condition acquired from some disease or injury to your retina, such as:

  • Neurological injuries;
  • Brain tumors;
  • Optic trauma;
  • Diabetes;
  • Glaucoma;
  • Multiple sclerosis;
  • Parkinson’s disease;
  • Alzheimer’s disease;
  • Waterfall;
  • Sickle cell anemia;
  • Kallman’s syndrome;
  • Chronic alcoholism;
  • Leukemia;
  • Leber’s hereditary optic neuropathy (LHON).


Certain medications can cause changes in vision, such as some used to treat heart problems, high blood pressure , erectile dysfunction , infections and nervous disorders.

Other medications can also cause problems in the optic nerve and cause difficulty in seeing some colors, they are:

  • Antipsychotics: Chlorpromazine (Amplictil) and Thioridazine (Melleril);
  • Antibiotic: Ethambutol (Myambutol), used to treat tuberculosis .

Other factors

Toxic chemicals, such as styrene and carbon disulfide, and the natural aging process can also contribute to the deterioration of the ability to distinguish colors.

Groups of risk

Color blindness is hereditary, that is, if any family member has a history of the disease, the individual has a chance of also having it.

Since the disease is genetically linked to the X chromosome, it occurs more frequently among men than among women.

Symptoms of color blindness

In some cases, symptoms may vary and be barely noticeable, however, it is common for the diagnosis to occur at the school age of children. Parents and teachers should be aware if they have difficulty distinguishing colors or an inability to see shades of the same color. Color blindness can also rarely cause rapid eye movements.

Diagnosis for color blindness

When suspecting problems in distinguishing certain basic colors, an ophthalmologist should be consulted to make a concrete diagnosis and the possible causes for having the disease. It is important that children receive eye exams before starting school.

There are four methods for diagnosing the presence of color blindness and determining how the disease is affecting color perception in the patient. Are they:

Nagel Anomaloscope

It consists of a device that emits yellow light in half of the visual field, while the other half is illuminated by several green and red monochromatic lights. The patient should touch the adjustment buttons and try to match the shades of the two visual fields, changing the intensity of the colors. By comparing the actual shade of color and that seen by the patient, the doctor will determine the degree and type of color blindness.

Holmgreen wool

It consists of small colored wools painted in slightly different colors, which the patient must separate into groups as determined in a template. The medical report is determined according to the distortion of the order of colors.

Ishihara color test

The Ishihara color test is the main method used to diagnose the disease and consists of the use of dotted cards in several different shades. Letters, numbers or geometric figures in the case of illiterate children are drawn in the center of the card, which contains several circles made of colors different from the colors located in its vicinity. The figure in the center is easily identified by people with normal vision, but a colorblind person will have difficulty visualizing them.

The numbers shown in the images are: 12, 2, 42, 74 and 6.

Farnsworth-Munsell Hue Test 100

It consists of using a set of blocks or pins of approximate colors, but in different tones. The test measures the ability to differentiate subtle color changes by arranging them in order of hue, from lightest to darkest. At first, it is mostly used in industrial sectors that depend on the color perception capacity of their employees, such as graphic design, photography and food quality inspection.

Treatment and cure

Color blindness does not evolve, but there is still no specific cure or treatment for people with the disorder. However, there are measures that can improve patients’ vision limitations, they are:

Special lenses and glasses

There are special glasses and lenses for color blind people that act selectively as to the passage of light, improving the perception and distinction of similar colors.


Tools made of colored filters that, when looking through them, more colors can be distinguished. They can be used, in some specific tasks, in certain professions or to assist in everyday situations.

Living together and complications

If they have a family history of color blindness, children should be tested to ensure that they are not carriers of the disease, since patients may have some limitations in their daily lives, such as difficulty in matching colors of clothes or choosing ripe fruits. However, the individual can make some adaptations to improve his quality of life, such as:

School children

At school age, the first difficulties with colors arise, as in drawings and maps, and those responsible should pay attention to these circumstances so as not to embarrass the child who claims to see different colors from his colleagues.

Being colorblind is no obstacle to development and learning, so schools must promote changes in materials to provide information to students with difficulty in distinguishing colors. Colored pencils can also have the name of each color engraved in order to facilitate their identification.


Color blindness is an anomaly that makes wearers see colors differently, so it is advised not to aim for professions that require perfect vision, such as, for example, airline pilots. However, it does not interfere very much if the bearer has a driver’s license, since it is possible to associate the position and colors of the traffic lights and assimilate their meaning.


Reading and understanding colored graphics and underlined texts are often impaired according to the color scheme used. Therefore, navigating colorful websites on the internet can be challenging for a colorblind person. Most of the time, the patient will see gray instead of colored text, which can lead to misinterpretation or loss of relevant information.

Currently, there are developed programs that make changes in colors and put them in different positions, in order to differentiate them and facilitate online navigation for a colorblind.


When it comes to a genetic inheritance, color blindness has no known forms of prevention. However, when it is an acquired defect, it can regress or stabilize as long as the cause is tackled or prevented in advance from frequent examinations.

To reduce the chances of acquiring changes in color vision, medications should be used only under the doctor’s prescription.

Color blindness is not a serious disease, but it requires adaptations to avoid possible difficulties and constraints to patients. Help more people to be aware of their symptoms by sharing this article!