Red Green weakness
Synonyms in a broader sense
Red-green blindness, red-green poor eyesight, dyschromatopsia, color blindness (coll), color ametropia, abnormal trichromatism, dichromasia
English: color blindness, daltonism
Also do the:
- Self-test red-green weakness
- Online eye test
- Amsler grid test
definition
The genetic red-green weakness is the most common color ametropia and is often incorrectly referred to as color blindness. The disease can be divided into red weakness (Protanomaly) and a green weakness (Deuteranomaly), with both the colors red and green being difficult to tell apart. Furthermore, a distinction is made between the rarer red blindness (Protanopia) and deuteranopia (Green blindness) where it is no longer possible to differentiate between the two colors.
Epidemiology
The red-green weakness is always innate and affects about 9% of all menr and 0.8% of women. Usually it intensifies or improves over the course of life.
history
That was discovered Red Green weakness by the English naturalist and teacher John Dalton (* 1766), who himself suffered from this disease. For this reason it is also under the name Daltonism known.
causes
The red-green weakness and blindness are X chromosomal recessive Hereditary diseases. This means that the gene that causes the disease is on the X chromosome. Women need two defective gene copies in order to fall ill; for men, one is sufficient, since they only have one X chromosome. This explains why men are affected much more often than women.
There are three different types of color receptors (cone types) in the retina in the human eye: red, green and blue cones. Each of them absorbs light in its specific color spectrum.
In the case of red-green weakness, there is now a mutation in the gene that is responsible for the red or green cones. As a result, a changed visual pigment (Opsin) that no longer allows correct color perception. In the case of red-green weakness, the gene is not only changed, it is completely missing, which is why the corresponding color is no longer recognized.
Symptoms
People with a Red-green poor eyesight perceive certain red and green tones only as shades of gray, which means that they are difficult or even impossible to distinguish between these two colors.
Most of those affected hardly perceive this disorder as bad, since it has been birth know no other way of seeing.
Apart from the ability to differentiate in the red-green area, patients also develop the same color impression as people with normal vision, which leads to an impairment that can only be assessed as minor. However, there are some professions that require very good eyesight, such as a pilot, bus and taxi driver or police officer, that you are not allowed to practice with this restriction.
diagnosis
There are several ways to get one Red Green weakness to diagnose.
With the help of special color tables, a red-green weakness can be identified and its severity determined. The most common are those named after their developer Ishihara color tablets (also pseudoisochromatic color tables called) use.
These panels (see: Self-test red-green weakness) are circles that are filled with round spots of color in different levels of brightness. With perfect color vision, a certain number, also composed of color spots, can always be seen in the center of the circle, which is determined by the ability to differentiate between red and green (or blue and yellow for the diagnosis of the much rarer green-blue weakness) becomes visible. Patients with a Color vision deficiency However, they cannot tell the different colors apart, but only notice the possible contrasts, which means that, depending on the board and the severity of their visual impairment, they see no number or a different number than the normal sighted person. The test usually involves looking at several tables, with the number 12 for each of them being visible on the first table. The panels after Stilling-Velhagen are based on the same principle.
The Farnsworth-Test. In this test, the person being examined should bring a certain number of colored buttons into a color row that appears correct to him. For the evaluation, the person carrying out the work has a piece of paper on which the correct sequence of the colored plates is arranged in a circle. On this piece of paper, he now connects the colored buttons as the test person lined them up, so this circle should have been created in the healthy person. The different types of color ametropia provide very characteristic patterns that deviate from this curve.
The last chance to Diagnosis offers the anomaloscope according to Nagel. Here the patient looks through eyepiece on a round test field. This is divided into two halves: The lower half is called "Reference field“Filled with a preset yellow (spectral yellow, sodium yellow). In the upper half, in the "Mixed field“, The patient should mix spectral green and spectral red in such a way that the same color impression is created as with the pure yellow and the circle finally appears monochrome. Someone with a weakness of green would have to add too much green to the mixed field in order to get the impression of sodium yellow, since they only perceive the green more weakly, a patient with a weakness of red would add too much red accordingly. A quotient can be determined from the quantitative values for the green and red used, which provides an exact statement about the degree of color ametropia / Red Green weakness allowed.
therapy
To date, there is no known therapy for red-green poor eyesight and since the disease is inherited, there are no options for prophylaxis.
Summary:
Red-green weakness is a congenital, very common, but not very serious disease that mainly affects men. In everyday life it is only associated with a very minor restriction, which many affected people often do not notice at all or only very late, because they are not used to anything else. In order to determine the malfunction or to describe it in more detail, there are various tests that are used, among other things, in recruitment examinations for pilots and police officers.
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