WHAT IS COLOR BLINDNESS? SYMPTOMS AND CAUSES - ARTE - 2025

The color blindness or color blindness is an eye deficiency characterized by an inability to see or differentiate colors under normal lighting conditions. The origin of its name comes from the chemist and mathematician John Dalton (1766 - 1844), who was the owner of this genetic defect.

Dalton noticed his visual impairment because he confused the flasks in his laboratory, causing an incident. In his work Extraordinary facts related to color vision (1794), he explains how color blind people perceived color and tried to give an explanation about the causes of the disorder.

Color blindness is the result of the absence or malfunction of one or more sensory cell cones in the retina. The cones are responsible for the light transformed into electrical energy reaching the brain through the optic nerve.

Types of color blindness

The severity of affectation is variable and can be classified according to the degree in three types of color anomalies.

Dichromatism

People who suffer from dichromatism perceive a smaller range of colors because they suffer from dysfunction in one of the three basic mechanisms of color. Three variants are known:

- Protanopia. Lack of pigments that absorb long wavelengths. The afflicted people do not perceive the color red and are only able to see blue or yellow tones.

- Deuteranopia: Lack of pigments that absorb medium wavelengths. The afflicted people see the green color in yellow tones.

- Tritanopia: Lack of pigments that absorb short wavelengths. Sufferers confuse yellow and blue and see only blue and reddish tones.

Anomalous trichomaticism

It is the most suffered. The individual presents all three types of cones, but they present some deficiency that prevents normal functioning, altering the perception of colors. It is divided into three groups: protanomalia, deuteranomalia, and tritanomalia.

Achromatopsia

More severe variant of color blindness. The individual only sees white, black, gray and all their shades, preventing him from perceiving any color. The reasons may be due to the absence of any of the cones or neurological reasons.

It is usually associated with amblyopia, sensitivity to light, low vision, or nystagmus (involuntary eye movement). Those with achromatopsia are very sensitive to sunlight.

Causes

The causes that cause deficiencies in color vision can be classified into two sections:

Genetic causes

The defect in most cases is genetic. This is transmitted through a recessive gene linked to the X chromosome.

Acquired

They are those that are not related to genetics. They are produced by several factors such as:

- Chronic diseases (Alzheimer's, diabetes, glaucoma, leukemia, multiple sclerosis or macular degeneration)

- Accidents or strokes that damage the retina or certain areas of the brain that lead to visual deformation.

- Medicines and drugs. Although there are several drugs that can cause this disorder, the drug hydroxychloroquine (Plaquenil), used for diseases such as rheumatoid arthritis, is the one that usually causes the most problems.

- Industrial or environmental chemicals. There have been cases in which carbon monoxide, carbon sulfide or lead can develop color blindness.

- Age. People over the age of 60 can experience physical changes that affect their ability to see colors.

Who is affected by color blindness?

Color blindness can affect anyone as it is due to a hereditary genetic problem. However, men are much more likely to suffer from it than women.

It is estimated that 1.5% of men suffer from color blindness, while only 0.5% of women have some impairment to distinguish colors.

This is because this disorder is linked to recessive gene mutations. Remember that women are made up of two X chromosomes, while men have one X and other Y chromosomes.

The X chromosome is where the genes that cause color blindness develop, as well as other diseases such as hemophilia.

If both sexes have the X chromosome, why does it affect the male more? The reason is that the other X chromosome in women compensate for the alterations. That is, they contain the healthy gene, which, being predominant, avoids developing genetic diseases most of the time.

However, man, who has the Y chromosome, cannot compensate for this type of genetic alteration and they are more prone to developing color blindness.

Thus, women can be carriers of the disease if one of their chromosomes contains the genes, but they can only develop it if they have both chromosomes affected.

Diagnosis

To confirm that a person is color blind, ophthalmologists conduct a simple test using the Ishihara letters. Designed by Dr. Shonobu Ishihara (1879-1963) at the beginning of the 20th century, the letters represent the most reliable, simple and economical method today.

The cards are made up of a series of circular dots in different shades that form a visible number for people with normal vision. In the case of a person who suffers from a color disorder, she will be unable to recognize any number.

Depending on the type of color blindness, cards with blue, green and brown tones (protanopia) or red, yellow and orange (deuteranopia) will be used.

To determine the level of color blindness, the test consists of 38 cards, although usually less than 20 are necessary to determine whether a person has the disease or not.

Ishihara's letters. In the image on the left, a person with normal vision sees the number 6, while a color blind person sees nothing. In the image on the right, a person with normal vision sees the number 2, while a color-blind person sees nothing.

The Ishihara charts are not the only method for diagnosing color blindness. Although its use is less frequent, there are several tests that can also be useful:

- Jean Jouannic test. Similar to Ishihar cards, with the difference that the image to be recognized can be a letter, number or geometric figure. It is often used for testing in young children due to its simplicity.

- Farnsworth test. The test consists of the patient ordering a series of color cards so that the colors are gradually ordered.

- Anomaloscope. It is an instrument used to diagnose the type and degree of chromatic alteration. It is the most reliable vision test, but its use is not very common due to its complexity and the cost of purchasing the model.

Although it is easy to find some of these tests on the internet, they are not entirely reliable since the brightness or contrast of the computer or mobile device screens can distort the image.

It is best to go to an optician's or an ophthalmologist's office to carry out the test correctly.

Color blindness in children

Many authors have shown that visual skills are closely related to academic performance. Good eyesight, resistant to fatigue and effective in certain tasks such as reading, is important in the first years of schooling.

Although at school the use of color serves as a code or material in various learning activities from early childhood education, few studies have been carried out on the influence of anomalies in color vision in the school context and there is little consensus when stating whether or not it affects schoolchildren.

According to Lillo (1996), “the group of color perception alterations known as 'color blindness' affects a significant percentage of male children in European countries, and given the importance of color materials in nursery school, it tends to make it difficult to school integration of children ”.

In contrast, a study published in the Revista de Educación (2003) about the performance of schoolchildren with color blindness in Early Childhood Education, states that there are 5% of children in classrooms who suffer from color blindness, but they have not been able to verify that this visual disorder affects significantly in their educational performance.

In any case, it is important to detect visual anomalies in children, whether or not they affect school performance, since it could be a bewilderment for the infant in their day-to-day life.

For this, ophthalmologists recommend that parents monitor their children through games such as the use of figures or pictures with the primary colors, perceive how they color in their drawings at home or school and of course resort to some of the methods color blind exams like the ones we mentioned above.

If a child suffers from color blindness from the moment the ophthalmologist diagnoses it, it is important to explain the reasons for his illness and make him see that it is not a problem, but a condition that can be overcome with certain techniques.

Does it have a cure?

Color blindness has no cure. The answer is clear as there is no known treatment and it is a lifelong disorder.

In recent times, some researchers have carried out experiments that they claim open a door of hope to the colorblind. We list a couple of them that had an impact in the media:

Glasses that cure color blindness

In 2013, American neurobiologists developed a kind of lens called Oxy-Iso that, according to its inventors, allowed to improve the perception of green and red colors in colorblind people.

However, its reliability is questioned since the testators of the device assure that the yellow and blue colors are no longer perceived.

Gene therapy

Researchers at the Universities of Washington and Florida, in the United States, experimented with squirrel monkeys, primates that are unable to distinguish green and red, with gene therapy.

They were implanted through a virus, corrective genes that repaired their color blindness, being a complete success. These genes made the retina of monkeys make opsin, a substance that makes visual pigments that are used to distinguish red from green.

The problem is that, to date, it is not proven that this genetic modification can pose a risk in humans.

Some curiosities

- 350 million people suffer from color blindness worldwide.

- 17% of people do not discover that they suffer from color blindness until after 20 years.

- Paul Newman, Mark Zuckerberg, William IV, Vincent Van Gogh, Bill Clinton, Mark Twain, Bing Crosby or Keanu Reeves are or have been color blind.

- In some countries like Brazil, the color blind cannot obtain a driver's license.

- Colorblind people cannot access some jobs such as airplane pilot, firefighter or police officer.

- Some color blind are unable to determine whether a banana or other foods are ripe or not.

- Although the Ishihara charts are the most famous diagnostic test, as early as 1883 Professor J. Stilling invented pseudoisochromatic dishes to detect color blindness

- The automobile company Ford and the University of Cambridge are working together to design a car adapted to people who suffer from color blindness.

References

1. Adams AJ, Verdon WA, Spivey BE. Color vision. In: Tasman W, Jaeger EA, eds. Duane's Foundations of Clinical Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013: vol. 2, chap 19.
2. Wiggs JL. Molecular genetics of selected ocular disorders. In: Yanoff M, Duker JS, eds. Ophthalmology. 4th ed. St. Louis, MO: Elsevier Saunders; 2014: chap 1.2.
3. Katherine M, William W. Hauswirth, Qiuhong L, Thomas B. C, James A. K, Matthew C. M, Jay Neitz & Maureen Neitz Gene therapy for red – green color blindness in adult primates. Nature 461, 784-787 (2009).
4. S. Ishihara, Tests for color-blindness (Handaya, Tokio, Hongo Harukicho, 1917.
5. Lillo J (1999) Perception of color. P. 301-338.
6. Montanero M, Díaz F, Pardo P, Palomino I, Gil J, Pérez AL, Suero I. Color blindness and school performance in early childhood education. Education Magazine, ISSN 0034-8082, No. 330, 2003, pp. 449-462.