Even if you have never met a person who is unable to distinguish between any colors, it must be said that color blindness is a fairly common disease of our time. Among the inhabitants of the planet, not only people can be color blind. Many animals are the "owners" of color blindness. For example, bulls are not at all familiar with the red color, but formidable predators, such as lions and tigers, know only blue and green. Similarly perceive the color scheme of cats and dogs. Walruses, whales and dolphins do not distinguish colors at all and see the world around them in black and white.
Why aren't all colors visible to the eye?
The retina of the human eye is a complex, multifactorial instrument of the organ of vision that transforms a light stimulus and allows you to see an object in its exact form and with all shades of color. It is equipped with photosensitive cones containing a pigment responsible for determining color. A person has three types of light sensors located on the retina, the so-called cones. In each - a certain set of protein pigments. Speaking in an unscientific language, each of these cones is responsible for the perception of a particular color: red, green and blue. In the case when one of the set of protein pigments is missing, a person loses the ability to perceive a certain color. With the normal functioning of all three sensors, a person distinguishes about a million shades of color, but with two - only 10,000 (100 times less). Color blindness is a deviation from the norm when the operation of at least one light sensor is disrupted.
People with color blindness hardly perceive shades, but they can recognize colors by brightness or by tones, cold or warm. Color blind people do not always know about their disease and do not notice their differences in perception from the feelings of other people. The memory helps them in this. It is the memory and brightness of the image that allows them to judge a certain color and compare it with another palette.
Types of Color Blindness
Color blindness also has many varieties. Sometimes a person has less than three color cones since birth. Hence the group of people on the perception of color :
• Trichromats (normal, all three cones of protein pigments function in the retina).
• Dichromats (only two cones function; problems arise with the recognition of many shades).
It was this deviation that John Dalton, an English naturalist, identified in himself and was the first to describe color blindness from his own point of view from a scientific point of view. He just belonged to the group of dichromates, when red and green colors are seen as different shades of brown-yellow color. D. Dalton wrote his first work on color blindness at the end of the 18th century.
• Monochromats (only one type of cone is functioning; in this case, a color blind test will show that people do not know about colors, the whole world is black and white for them).
Abnormal Trichromats
There are deviations in people whose retina is equipped with all three light sensors, and it would seem that all colors should be perceived. The problem may be the so-called color dips. The fact is that, ideally, the sensitivity zones of light sensors, the eyes responsible for the perception of a certain color should overlap each other, necessarily evenly. This allows the eye to perceive all shades when moving from one color to another: from blue to green, from green to yellow, from yellow to orange and beyond. When the sensitivity zones are shifted (overlapping one another), they begin to argue, the shades are layered, the pure colors fade. The brain gets confused and begins to identify some colors as just gray. This is called abnormal tri-color vision.
Congenital color blindness
A partial or complete inability to distinguish colors is a hereditary or acquired pathology (much less common).
Hereditary color blindness is a recessive sign of inheritance associated with the pathology of the X chromosome, therefore, more often the disease is inherited from the mother by the boys.
As you know, the female embryo is the carrier of two X chromosomes. But for normal color perception, one healthy X chromosome will be enough. For girls, the disease only spreads when both mother and father suffer from color blindness. But in this case, according to the laws of genetics, color blindness in women with only one chromosome with the affected gene, which did not appear in the carrier, can be inherited by the son. But this will not necessarily happen. The color blind gene can be transmitted even after several generations. Again, the male population is more likely to be at risk.
According to statistics, color blindness in women is recorded only in 0.1% of cases. Among men, color blind people are 8%. With a hereditary factor, color blindness is, as a rule, a pathology of both eyes that does not progress over time.
Color blindness acquired
The main factors affecting the acquisition of color blindness are always directly or indirectly associated with either brain injuries or damage to the retina. Sometimes a concussion received in childhood can subsequently affect color perception. In addition to childhood injuries, other factors can influence the acquisition of color blindness:
- Old age.
- Eye damage due to injury.
- Concomitant eye diseases (glaucoma, cataract, etc.).
- Drugs that have a side effect.
Diagnosis of color blindness. Testing
Color blindness is a given that you just need to accept. He is not being treated. This is the same as a musical ear: someone has it, but someone does not. Never need to do self-diagnosis. If you notice a deviation in the perception of color in yourself or your children, you need to contact a specialist. There are proven methods for determining color blindness and its type.
1. Rabkin's test (polychromatic tables).
Color blindness testing in this test is done by looking at tables that show various numbers or letters. Readable images are applied using color spots that are the same in contrast and brightness. The result of the test will be the subject's ability to recognize the desired numbers or letters in the images.
2. Test Ishihara.
A similar test in the form of tables that allows you to more accurately determine moderate, severe degree of color blindness and complete color blindness. There is a full edition of this test of 38 tables. They are used by professional ophthalmologists.
An abridged version of 24 tables is used for rapid testing when hiring municipal institutions, airports. There is also a short specialized edition of 10 tables for preschoolers and illiterate people. Instead of letters and numbers, these tables use images of geometric shapes and various lines.
Color blindness and the profession of man
The limitations with which a color blind professional can be associated are very important. First of all, these restrictions apply to professions where there is responsibility for life, one's own or other people. Color blind people are not accepted for military service, cannot be pilots of aircraft, drivers of commercial vehicles and chemists. For these professions, annual medical examinations are mandatory, which are admission to professional activities. If a person is examined for color blindness, the rights in his profession are sharply reduced. He can engage in theoretical training of young specialists, perform office work related to his professional skills.
Color blindness and driver's license
If in some professions, color blindness is a sentence, then to obtain a driver’s license, the restrictions do not apply to everyone. The opinion of a specialist is important here.
Driving license and color blindness are completely compatible concepts, but only after the conclusion of an ophthalmologist. Only a doctor determines the type and degree of color blindness, therefore, and issues permission to the patient to drive a personal car. Color blind people can obtain the rights of categories "A" and "B", which will necessarily have the mark "Without the right to work for hire."
To help color-blind people
Scientists regularly offer new medical "gadgets" that can ease the plight of people with disabilities. It turns out that despite the fact that doctors cannot fix the cone-sensors, it became possible to reprogram the brain to the correct color perception. Today, special glasses have appeared, in which narrow spectral stripes are simply “cut out” by lenses and pure colors are separated from each other. The principle of contrast enhancement allows the red, blue and green colors not to mix.
Science has helped many color blind people see colors that they did not even suspect existed: purple, bright green, and bright red.