anomaly in color

Daltonism or Color blindness is not strictly speaking a visual pathology, but rather a feature that modifies the perception of colors. Genetically transmitted, this anomaly will last a lifetime without aggravation or improvement.

1. What is Daltonism

The most famous color blindness of dyschromatopsia (a disease affecting color perception). Described by the English chemist John Dalton in the 18th century. Color blindness is a genetic disease that affects the sex chromosomes Y and X. If the normal eye perceives the three basic colors thanks to three types of retinal cells called "cones," the color blind may suffer from a malfunction of its cones or not have one at all.

2. Daltonism; What are the 3 types of color blindness?

There are conventionally three types of color blindness:

2.1 Monochromatism or Achromacy

Monochromatism is a disease of the visual system that manifests itself in a complete lack of color vision. The vision is in shades of gray; this disease is very rare, but its symptoms can be distressing.

2.2 Dichromatism

Dichromatism means that only two of the three cones are working, and the one which is not working determine the type of dichromatism you have:

Deuteranopia: is the absence of cones receptive to green; affected people are unable to perceive green.

Protanopia: The absence of cones receptive to red, affected people do not perceive this color.

Tritanopia: is the absence of blue receptive cones.

2.3 Abnormal Trichromacy

We speak of abnormal trichromatic when the three types of cones perceive light, one of which does not function correctly, inducing reduced sensitivity to a certain color depending on the cone affected:

Deuteranomaly: mutation of receptors that identify average wavelengths, those related to the color green. This is the most common type of abnormal trichromatic.

Protanomaly: mutation of receptors that identify long wavelengths, those related to the color red.

Tritanomaly: mutation of receptors that identify short wavelengths, those involving the color blue. Tritanomaly is the rarest form of color blindness.

3. Daltonism; Causes

The retina, a membrane lining the back of the eye, is sensitive to light and color. It has specialized cells, called cones, which are sensitive to colors. There are 3 types of cones. One distinguishes red, the other green, and the last blue. When one type of cone does not function normally, the color to which the cone reacts is difficult to distinguish. For example, a person who cannot distinguish red has an abnormality in the cones corresponding to that color.

Most cases of color blindness are inherited; however, some cases are due to injury or disease of the retina or optic nerve that receives and transmits information from the eye to the brain. People inherit color blindness through an abnormality in the color genes located on the X chromosome.

Men are 10 times more likely to inherit it than women. Since they only have one X chromosome, if it is damaged, color blindness occurs. While for women, who have 2 X chromosomes, the healthy gene on one chromosome can compensate for the diseased gene on the other. A woman can have a sick gene that doesn't necessarily show up, but she can pass it on to her children. A person is said to be a carrier when they can transmit a genetic disorder, such as color blindness, to their offspring without being affected themselves.

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4. Daltonism; Symptoms

An erroneous perception of colors, therefore, manifests color blindness:

People with normal vision are "normal trichromats," that is, they have all three types of cones and see all the colors.

While color blind people are dichromats: they only have two types of cones, usually blue and green. Because of this, they perceive only three shades: blue, yellow, and an intermediate white or gray shade. The absence of blue or green cones is much rarer.

Exceptionally, two or all three types of cones may be missing, leaving the person seeing black and white. We speak of "monochromatism" or "achromatopsia." Conversely, sometimes the cones are present but do not perfectly transmit the signal corresponding to their color, which leads to a slight deterioration of colored vision. Those affected have "abnormal trichromatism."

Certain diseases, such as diabetes or glaucoma, can cause reduced color vision, which is often not perceived by patients. Unlike color blindness, these "dyschromatopsias" can worsen as the disease progresses.

5. Daltonism; Age, transmission, and tests

5.1 Age

Since color blindness is an inherited condition, it manifests itself from birth. We can detect color blindness from an early age, during an ophthalmological examination.

5.2 Transmission

In most cases, color blindness is inherited and depends on chromosome 7 and sex chromosome X. The transmission is, therefore, by one or both parents in very rare cases.

6. Daltonism; Diagnostic and tests

Tests for color blindness are usually done on children and on job applicants for which color discrimination is essential, such as a pilot, train driver, or electrician.

The performance of the color blindness test must be in daylight, using special cards of different colors. A more complicated test requires an instrument called an anomaloscope; it produces a changing mixture of red and green light. The person under test should adjust the mixture of colors until they get a yellow light; thus, the specialist can determine the degree of Daltonism by observing the tendency to red or green of the mixture.

7. Daltonism; Treatment

No treatment is currently able to restore normal color vision. Some opticians offer glasses and contact lenses, supposed to compensate for abnormalities in color perception, but these products remain to perfection.

However, color blindness does not result in an actual disability; the person has his own frame of reference, where a replacement of missing shades is with different shades of gray. The existence of this anomaly does not increase the risk of visual failure and does not require any special monitoring. The main disadvantage of color blindness is that it prohibits certain professions, such as public transport. On the other hand, the lack of vision of certain colors is undoubtedly an advantage in graphic areas.

Originally published on Live Positively.