Color blindness of the eyes

Color blindness means having trouble recognizing red, yellow, blue, or a combination of these colors.

It is rare for a person not to see a single color.

Colorblind people do not perceive colors. This is a congenital disease that affects men more often than women.

Red-green visual impairment is the most common form of color blindness.
In rare cases, a person may inherit a gene that restricts the ability to recognize shades of blue and yellow.
This lack of yellow or blue color vision affects men and women equally.

Police officers, firefighters and pilots are among the professions that require normal color perception.


Types of color blindness

Names that indicate a color deficiency are:

  1. protanopia for red blindness,
  2. protanomaly for red vision impairment,
  3. deuteranopia for green blindness,
  4. deuteranomaly for green vision impairment,
  5. Tritanopia for blue blindness,
  6. Tritanomaly for blue vision impairment.

Protanopia, deuteranopia and tritanopia are types of dyschromatopsia. This means that compared to the three receptors, people with normal color vision have only two different receptors (cones) for the three colors.

There are people who are affected by complete color blindness, also called achromatopsia or monochromasia.
Those who suffer from this disorder have only one type of color receptors.

Protanomaly (the frequency is one in a hundred in men):
Protanomaly refers to the difficulty of seeing red.
Red is perceived in a different tone and tends to green.
Everything appears brighter than with a normal viewer. The amount of red that a normal observer sees in a violet or lavender color is weaker for someone with protanomaly, because he cannot recognize this color and only perceives the blue component.
The greatest difficulty is when driving, because a person with this type of color blindness cannot distinguish between yellow and red at a traffic light in dense fog, blinding sunlight or other blinding situations.

Deuteranomaly (the frequency in men is five to hundred):
A person with a deuteranomaly has a reduced perception of green components. This person has difficulty perceiving small color differences in the spectrum of red, orange, yellow or green.
For a colorblind person with a deuteranomaly, these colors tend slightly to red.
A very important difference between people with deuteranomaly and protanomaly is that the former do not feel the problem of loss of “brightness”.

Protanopia (the frequency in men is one in a hundred):
Protanopes can not perceive red color. This defect can be so pronounced that red is confused with black or dark gray. A red light can therefore be interpreted as switched off.
Those affected can learn to distinguish the colors red, yellow and green mainly by their brightness and not by possible perceived differences in hue.
Purple and lavender colors are indistinguishable in their different shades of blue, because the red component is so dark that it remains invisible.
For example, pink flowers reflect both red light and blue. They can appear to people with protanopia only blue.

Deuteranopia (a man in a hundred):
People with deuteranopia suffer from the same problems of hue discrimination as protanopes, but do not recognize the color green.
The cones sensitive to the wavelength of green are completely absent and this type of colorblind people can only see two colors instead of seven.

Inheritance of red-green blindness

The most common form of color blindness (red-green) is caused by a recessive gene located on the X chromosome.
The mother has an X chromosome pair, the father an XY chromosome pair.
Genetically, each mother and father contributes chromosomes that determine the sex (male or female) of the child.

  1. If the X chromosome unites with another X chromosome, it forms an XX chromosome pair and the child is a girl.
  2. If the X chromosome joins a Y, the child is a boy.

If the son is colorblind, the cause is a recessive gene that is ONLY on one X chromosome (as in hemophilia).
To have this defect, the mother must be a carrier of the gene.
The father with this hereditary red-green color deficiency inherits the X gene to his daughters, but not to the sons, because a son does not receive the X chromosome from the father.
The daughter inherits the gene, but rarely inherits the disease because the gene responsible for color blindness is recessive.
This means that in at least one normal X chromosome, the daughter is not colorblind.

If a daughter inherits the trait attached to the X chromosome of the father and mother, she will be colorblind and also a carrier.
Every time a mother transmits this trait to a son, he inherits the color vision deficiency and finds it difficult to distinguish green from red.

If a woman has red-green blindness, all male children are colorblind.

What are the causes of color blindness?

Most problems of color blindness are hereditary (genetic) and present from birth.
Humans usually have three types of cone cells in their eye.
Each species perceives a different shade:

  • red
  • green
  • blue.

You can recognize colors when the cone cells perceive these three primary colors.
Most cones are located in the macula, i.e. the central area of the retina.
Hereditary color blindness occurs when these cone cells are not present or when they do not function properly.

You can’t see one of these three primary colors, or you can see them in a different hue of that color or another.
This type of difficulty in color perception does not change over time.
A color perception problem is not always hereditary. In some cases, a person may have an acquired problem with color sensitivity.

Possible causes of acquired color blindness are:

  1. Age
  2. complaints with the eyes such as glaucomamacular degenerationcataracts or diabetogenic retinopathy,
  3. trauma or eye injury,
  4. Side effects on some medications.

What are the symptoms of color blindness?

  • You may be able to see some colors but not some others.
    For example, you might not be able to tell the difference between red and green, but you can see blue and yellow.
  • You can see many colors, but you don’t understand which color is different from the others.
  • You can only perceive a few hues, while most people see thousands of hues.
  • In rare cases, you can only see black, white and gray.

Diagnosis of color blindness

The most common tests used for color blindness are:

  1. pseudoisochromatic Ishihara colour charts,
  2. Farnsworth test,
  3. Anomaloscopy.

Only the entire series of tests for color blindness can reveal the true nature and severity of the disorder.

The Ishihara color charts are usually used to detect color blindness and acromatosia.
The Ishihara test is a set of panels with different color wheels of equal brightness.
The patient must look at the boards and recognize what numbers are written on them.

There are 38 boards where numbers have to be recognized, paths to follow with a pencil (for children) or confusion boards that show the numbers only to the colorblind.

  1. The first board has the number 12 marked and serves as an example to explain the test to the patient, since the number is perceived by everyone.
  2. From the 2nd to the 17th test board, patients cannot read the numbers properly if they have problems with the colors of the red-green axis.
  3. Tables 18 to 21 do not contain numbers, but those who have a red-green weakness can recognize numbers.
  4. Tables 22 to 25 make it possible to understand which colour is not perceived and therefore the nature of the disorder (protanopia or deuteranopia, depending on whether the visual impairment is red or green).

The test must be carried out at a distance of 30-40 cm from the panels with appropriate lighting.
It can be done for one eye or both eyes.
Birth defects always affect both eyes.
Acquired errors (for example, cone dystrophy) affect only one eye.

Therapy for color blindness

There is no treatment or definitive cure for color blindness.

Colored lenses or glasses can improve the differentiation of colors within the problematic spectrum, but cannot produce normal color perception.
Some people use special lenses to improve color perception. These are filters in the form of contact lenses or glasses.
This type of lens is available from a limited number of ophthalmologists in the United States and other countries.

Some strategies can improve the ability of color perception.
Most people are able to adapt to color blindness without much trouble.
Unfortunately, some professions, such as commercial artist and working with electrical cables of different colors, depend on correct color perception.

One can also learn different methods to deal with color blindness. For example:

  • You can label the clothes to avoid wrong color compositions (friends and family can help with this).
  • Instead of the colors, you can remember some elements to determine an order.
    An example of this is to realize that at a traffic light, the upper light appears red, while the green light is at the bottom.
  • New applications for the Android and Apple devices can help in recognizing the colors.

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