Examination of color vision
General
Color vision is made possible by our so-called color sense. We have this because our retina has sensory cells that can perceive colors. These sensory cells are called "cones".
Color vision is made up of various properties of vision. The eye has the ability to perceive the hue, saturation and brightness of light.
The normal eye can distinguish up to 150 different color tones in terms of brightness. However, if it is dark, our eyes are quasi “color blind” and can only differentiate between lightness.
Now only the second type of sensory cells in our retina, which are responsible for black and white vision, are working, the rods.
Hence the saying “All cats are gray at night”.
Examination of color vision also makes sense if night blindness is suspected.
Examination of the color sense
Checking color vision is very easy to do. Everyone has seen the Ishihara color tablets before.
They are circular and consist of many small dots of color. In the middle of the circle there is a number that differs in color.
While people with normal sight can recognize the number without any problems, the color weak reads either a wrong number or no number. The principle of these tables is that all color points on the Ishihara table have the same saturation and brightness. They can only be distinguished by their color. For the color unfit, these points all look more or less the same gray.
These tables are the best way to determine the red - green weaknesses of the population. The extent, however, whether there is a red-green weakness or a red-green blindness, cannot be determined in this way.
A more detailed analysis of the color weakness can be carried out with the so-called anomaloscope.This is a device in which a certain color is specified, which must be restored by the patient by mixing red and green. Depending on how much of each color has been mixed in - which can be read on a scale on the device - there is either a red or green weakness.
If, for example, there is a green weakness, the person concerned mixes in too much green. The so-called anomaly quotient, which is important for certain professions (police officer, pilot, etc.) is determined from the mixing ratio.
What exactly is color blindness?
Red-green weakness or blindness is a congenital disease.
Men are affected more frequently than women. This is because the condition is inherited on the X chromosome. Since men only have one of these genes (the other is the Y chromosome), the disease strikes as soon as they have this gene on their X chromosome. In women, a defective gene is, so to speak, compensated for by an intact one on the second X chromosome.
Around 8 percent of men suffer from such a color weakness.
In most cases of color weakness it is a question of a red-green sensation disorder.
Yellow-blue weaknesses are also extremely rare. Complete color blindness also rarely occurs. The function of the pin has failed here. In the twilight, however, the latter patients see exactly like the normal sighted, who can then no longer distinguish between colors.
In addition to the innate color weaknesses, there are also acquired species. As soon as the center of the retina or the region around the optic nerve is affected, color perception is disturbed. This happens, for example, if the pressure in the eye is too high (green star = glaucoma), and so the optic nerve is squeezed. See also our topic "Green Star"
