The ability of a person to see different colors and shades is due to the proper functioning of the organs of vision. Such a process in medicine is called color perception. Due to the fact that modern society spends most of the time in front of the gadget screens, various visual impairments are increasingly recorded . Including the wrong perception of the color spectrum.
How to determine such a pathology? To do this, use medical instrumental methods or specially designed tests for color perception. What are these diagnostic methods and whether it is possible to check eyesight at home, we will tell in our material.
What is color perception?
First, clarify what color perception is. This is the ability of the human organs of vision to perceive light reflection and transform it into a holistic image. Various external physical factors influence the shade of a person in front of him: lighting, angle of refraction, distance, and even the psycho-emotional state of the individual at a particular moment.
There are different theories about the mechanism of color perception. Common is the so-called three-component. Its essence lies in the fact that the ability to color perception is activated under the influence of green, red and blue. If a person distinguishes between such colors and their shades, then such a color perception is called trichromasia in medicine. Color perception tests are developed precisely on the theoretical foundations of this theory.
Color Impaired
Unfortunately, in the age of electronic gadgets, few can boast of excellent vision. Color disturbance is one of the most common pathologies. Such deviations in medicine are called color blindness. Color blindness can be complete - then a person sees everything around in gray, or partial. Most often, disturbances occur in the green and red parts of the spectrum. Such vision problems are not only acquired, but also congenital.
It is especially important to pass a test for color perception for drivers, since usually people do not even realize that they see colors distorted or do not distinguish them at all. And this condition is extremely dangerous for people driving a vehicle, and pedestrians.
Diagnostic Methods
How is color perception of a person diagnosed? In modern medicine, there are two methods for identifying such pathologies of vision:
- instrumental using an anomaloscope (there are various models: Nagel, Rabkin, GOI);
- color perception tests.
The first method involves examination in a special medical center, which is equipped with the specified equipment. But the tests can even be done independently at home.
Tests for the diagnosis of color blindness
In modern ophthalmology, color perception is checked using special tables (Ishihara or Rabkin). They represent a certain system of multi-colored dots. It is not difficult for a person with normal visual perception to determine what is depicted on such cards. But patients with impaired color perception will not be able to distinguish a “hidden” figure or figure from the dots.
The most popular are Rabkin cards. They are divided into 2 groups:
- To diagnose the type of color perception disorder (these are tables 1 to 27).
- To confirm the preliminary diagnosis (tables 28 to 48).
How is the test conducted?
Using this test, it is easy to check your eyesight even at home. The color perception of a person at the first stage is diagnosed using tables 1 to 27. In order for the results to be true, the following diagnostic recommendations should be followed:
- The test should be carried out in natural daylight. In this case, the patient should sit with his back to the light source, and the examiner - opposite him at a distance of 1 meter.
- It is important to diagnose with normal patient well-being. Symptoms such as headache, weakness, fatigue, depressive and stressful conditions can lead to false results.
- Color tables should be shown to the subject vertically at eye level.
- The patient is given up to 7 seconds of time to think about the answer.
The answers of the subject are recorded in a special form for the convenience of their further interpretation and diagnosis of color perception disorders.
Rabkin Tables
What is the Rabkin table? This is an image of numbers and geometric shapes, consisting of dots of different colors. But the saturation of the palette is the same. Thus, a person with a normal color perception can easily see an “encrypted” image. Whereas in the presence of pathologies, it will be difficult for the patient to highlight the colors and build an integral picture.
It should be noted that the first two tables are the so-called trompe l'oeil. First, they are training. And secondly, they determine the simulation of the disease, since even a person with impaired color perception can decipher the figures depicted on them.
Decoding tables
In order to decipher the result, knowledge of the correct answer of each table is required, as well as the diagnostic purpose of each card. So, the answers to the Rabkin test are as follows:
- The first table shows the number 96. This card is intended to explain the test.
- On the next you can see the figures - a square and a triangle. The goal is to identify the simulation.
- On the card under this number is the number 9. If the patient is color blind, then he will see the top five.
- On the fourth table, normally a person sees a triangle, and in the presence of visual impairment - a circle.
- Rabkin's table at number 5 contains the number 13. With color blindness, the subject will see 6.
- There are 2 geometric shapes - a circle and a triangle. But a person with impaired color perception will not be able to distinguish between figures.
- This card is also a "trick". The figure 9, depicted on it, will be seen by both healthy people and those with color perception impairments.
- The drawn five will be seen only by healthy people.
- If there is a pathology of perception of the red color spectrum, then the subject will find the figure 8 or 6. On this table, while the nine is actually depicted.
- A person who sees the numbers 68, 66 or 69, there are deviations in color perception. In the absence of anomalies, the subject will detect the number 136.
- This card will be solved both by healthy people, and with pathology of sight. The number 14 is indicated here.
- The number 12 patients on this card will not be able to detect the red spectrum poorly.
- A circle and a triangle are drawn on this table. People who have an anomaly in the perception of the green spectrum can only see the triangle. If the orientation in the red part of the spectrum is disturbed, then patients will only find a circle.
- Here the numbers 3, 6 and 0 are encrypted. With an anomaly in the green spectrum, people see one and six. And if the color perception of red is impaired, then the numbers 1, 0 and 6 will be marked by patients.
- Only healthy people can see encrypted geometric shapes (triangle, circle and square). In the presence of pathologies, patients will offer a variety of answers.
- On this card, a healthy person will see the number 96. If the perception of the red spectrum is impaired, only nine will be noticeable. In case of problems with orientation in the green area, the patient will indicate only six.
- This table shows geometric shapes such as a triangle and a circle. In the presence of anomalies, a person will be able to detect only one of these figures.
- This table is different from the previous ones. Here a healthy person will see horizontal and vertical rows of multi-colored squares. Whereas in case of violation of color perception, the subjects note the uniformity of individual rows or columns.
- The number 25 is encrypted on this card. If there is an anomaly in vision, a person will see only five.
- If the subject distinguishes geometric figures on this table (circle and triangle), then everything is in order with his color perception. Color blind can not distinguish between pictures.
The remaining 7 tables are identical to those already described.
Interpretation of Results
So, the verification of color perception. How to decipher the results? Any number of incorrect answers gives reason to suspect a violation of color perception. In this case, the second stage of testing is carried out using tables 28-48 to clarify the form of pathology. But the final diagnosis can only be made by an ophthalmologist.
Color perception tests are a quick and affordable way to diagnose visual impairment. But it is important to remember that if all recommendations are not followed, the results may turn out to be false. Therefore, you should not engage in introspection, and even more so treatment, without consulting a specialist.