The world around is painted in a variety of colors and shades. The eyes of a person are able to catch this color variety. For many, it is important to choose clothes in matching colors. For others, it is important to arrange your own interior in pleasant colors. Still others cannot imagine their life without admiring the beauty and picturesqueness of nature. What would life be like if a person saw everything in black and white? And how do people with color blindness see it?
Color perception
The human eye is able to see colors due to the diversity of the emission ranges of the light spectrum. The retinal cone apparatus is responsible for this function.
There are three groups of color waves:
- Longwave - orange and red colors.
- Medium wave - green and yellow colors.
- Shortwave - cyan, violet and blue colors.
The main colors are red, green and blue. When mixing these colors in various proportions, you can get many shades that the eye perceives.
Sometimes there are irregularities in the cones, and the eye cannot distinguish colors. Such violations most often affect the male half of the population.
To determine the pathology of color perception in humans, tables are used to check color perception.
The first study of the phenomenon of color blindness was begun in 1794 by a scientist from England named John Dalton. This scientist did not distinguish red, like his two siblings. In honor of him, this visual disturbance was named.
Color blindness
The inability of the eyes to distinguish between color shades is defined as color blindness.
Scientists have revealed that there is a congenital disorder of color perception and obtained in connection with some factors. There are 16 times more men with this pathology than women.
Color blindness differs in three ways:
- With the inability to clearly distinguish the red color, this condition is called protanomaly (protos - from the Greek. First).
- If the eye is disturbed by the perception of green - this is called deuteranomaly (deuteros Greek second.).
- When the perception of blue is impaired, this is tritanomaly (tritos from Greek: treti).
In turn, color blindness of red and green colors is divided into types:
- C - a slight deviation from the norm of perception of colors.
- In - a significant deviation from the norm of perception of colors.
- A - complete loss of the ability to perceive green or red.
This pathology is determined by the table of vision and color perception testing.
Types of Color Blindness
With the loss of ability to distinguish one of the colors, a person is called dichromate. A person with a normal perception of the color gamut is called trichromat.
In the complete absence of perception of red, the pathology is called protanopia, green - deuteranopia, blue - tritanopia. If one of the three colors is not perceived, the perception of the other two is disturbed.
A rare type of color blindness, when a person distinguishes only one color from three (monochromat). And the most rare case, with a complete lack of perception of colors (achromasia), when a person sees everything in black and white.
In assessing the visual ability to distinguish colors, polychromatic tables are used to check color perception.
Reason for color blindness
Color blindness is not a disease, it is a genetic anomaly inherited. The altered gene crosses the female line, but women themselves almost never suffer from color blindness at the same time, but their children, boys, have a great chance of getting this ailment.
Color blindness can occur not from birth, but as a result of trauma, surgery or as a reaction to the use of drugs.
All color blind people see colors differently, depending on the degree of mutation of the cone apparatus of the eyes.
The cause of color blindness has not been fully studied, but it is believed that this is the result of evolution as an adaptation to the environment.
As color blind people see
It is clear that color blind people perceive the world differently than people with normal color perception. But, getting used to just such a vision from birth, they learn to live with it.
Many color blind people can see colors against a background of a different color, while ordinary people see only one color.
On the tables for determining color perception, color blind cannot distinguish the background color of the displayed figure or figure on it a tone lower or higher. He sees all parts of the image in the same color.
When is color blindness a problem?
A person suffering from a violation of color perception may not know about his ailment. But there are a number of activities in the implementation of which it is important that the human eyes perceive all three basic colors of the spectrum.
Drivers must distinguish between the color of traffic signs, position lights and brake lights on vehicles of other road users, as well as the color of traffic lights. That is why when undergoing a medical examination to obtain a driver’s license, it is mandatory to pass a test using the color perception check tables for drivers.
Workers using special equipment must distinguish between color signals.
In medicine, it is very important to distinguish between shades and colors for diagnosis and surgery.
It is equally important for the confectioner to distinguish between shades and colors to create delicious and colorful cakes and pastries.
Methods for the diagnosis of color blindness
Usually the diagnosis of Color blindness is made as a result of a planned or random medical examination by an ophthalmologist. The patient is offered to look at the tables for checking the color sensation of Rabkin and Yustova or examine his eyes with the help of the Rabkin Spectral Anomaloscope instrument.
With the help of these studies, it is possible to determine whether it is congenital or acquired.
Tables are square or round pictures, which depict small colored circles in the form of numbers or figures on the background of small circles of a different color. Color blind all circles in the picture see the same color and can not distinguish the figure or figure depicted on it.
Color Tables
Professor and ophthalmologist E. Rabkin, B. in 1936, created his first polychromatic table for the study of color vision.
These tables allow you to determine the type of color blindness and its complexity. Ophthalmologists use these tables all over the world.
Circles of the same brightness form an image where, in the background of some circles, others are encrypted in the form of a figure or number.
In total, there are 27 tables defining each individual violation of color vision.
Some hidden figures and numbers are seen by people with good color perception, in other pictures hidden images are visible only to color blind people.
In the diagnosis of color blindness, tables are often used to check color perception Yustova E. N.
Her tables are square pictures, each of which consists of two colors. In the center of one such picture is a square without one wall. The central square and background are different in color. These pictures are depicted in the form of small squares closely spaced.
To determine the anomalies of vision, Yustova created 12 variants of pictures.
In the study, it is necessary to determine which side of the central square does not have a wall (above, below, left, right).
Evaluation of color perception using tables
When examining color perception using Rabkin's technology, polychromatic cards are placed in front of the subject in a well-lit room. Light should fall directly on the pictures. At a distance of half a meter to a meter, the subject must distinguish between the drawings hidden in the tablets. One image should take no more than five seconds.
If a visual anomaly is checked in a child, he is offered to circle the figure or figure that he sees with a finger or a brush.
If the final conclusion is difficult or there is a suspicion that the subject has memorized tables with answers for checking color perception, there are control tables in the Rabkin set. There are 22 of them. Trichomata with normal vision correctly name all the colors, shapes and numbers indicated on them. Dichromats are able to name only 10 of them.
To reduce the time spent on this study, it is enough to take three cards with the most difficult image and show them to the subject several times.
In difficult cases, resort to tables in addition to determine the threshold color perception. With their help, the line is determined when a person ceases to see the hue and color saturation. This is called color strength.
The test is carried out in sufficient light. The test subject is invited to look at the tables through a special mask with a round hole. 12 tables are composed of red, yellow, green, blue and gray. On 11 of them there is a scale with options for a smooth transition from white to saturated color tone. On one remaining black and white field, so that the subject knew what to look for.
Tables are counted in order from left to right from top to bottom.
Each card consists of 36 squares arranged in a square of 6 x 6 squares. 26 of them have a primary color, and 10 cells located in the form of a “P” or a square without one side have the same color, but differ in tone. The test subject must determine which side the square does not have a wall on. On each next card, the difference between the main color and the central square becomes more noticeable.
The positive side of this study is that it cannot be faked. Subject will not be able to memorize answers to cards. While Rabkin, when examining the drivers of the table for checking color perception with the answers to memorize and falsify the results is not difficult.
The disadvantage of Yustova's tables is the quality of the image and color reproduction, which can be impaired when using poor-quality paper or ink from a printing device.
The test subject separates each field of vision from the rest using a round hole. Fields must be reviewed at least three times each for a reliable result.
results
If during the study of color vision using Rabkin tables all 27 tables are named correctly, the color vision of the subject is considered correct.
In the absence of red in the spectrum, 7 tables are usually correctly called, in the absence of green - 9 tables, and if blue is indistinguishable, 23 tables are correctly called.
When using Yustova's tables, the degree of vision of shades of one color is determined, which change from more saturated to barely distinguishable. If the perception of red is impaired, the test subject cannot determine the direction “P” on plates 1-4. In violation of the vision of green, 5-8 tables are not distinguishable. Problems with blue color help identify 9-11 tables.
Each table belonging to a particular color group, in order, has its own threshold of difference 5 - difficult to distinguish, 10 - less difficult, 15-20 - medium complexity, 30 - the simplest difference.
A gradual increase in the difficulty of distinguishing between the cells of the tables reveals congenital and incipient deterioration due to color vision disease. And also allow you to control the dynamics of healing.