Red-green vision impairment makes it difficult for affected individuals to distinguish between the colors red and green. It can vary in severity. While some hardly notice it, for others it makes the world much less colorful. This can then lead to problems in some everyday situations.
What is red-green vision loss / red-green blindness??
Red-green vision deficiency actually includes two color vision deficiencies: red vision deficiency and green vision deficiency. The photoreceptors of the retina are impaired, which normally react particularly sensitively to red or green light. These photoreceptors are accordingly called red cones or green cones. In red-green vision deficiency, red cones react more strongly to green light instead of red light, as is the case with people with normal vision. So they function almost like the green cones, so that affected people cannot distinguish red and green well. The more the red cones respond to green light and the less they respond to red light, the less they see red and the more difficult it is for the affected person to distinguish between the two. In the case of green-blindness, it is the other way around.
Is red-green blindness the same as red-green deficiency??
A Red-green blindness is not the same as a Red-green deficiency. In red-green blindness, the red cones or the green cones are completely missing. In this case, the affected person can no longer perceive the color. He is blind for red or for green. Sometimes both types of cones are missing and therefore the affected person is blind for red and green.
Difference between color blindness and red-green vision deficiency
The Red-green vision deficiency is not color blindness. Color blindness is when the affected person cannot see any colors at all, but perceives the world only as contrasts of light and dark. Color blindness is much rarer than red-green vision deficiency and affects men and women equally. Color blindness is also often accompanied by other symptoms such as reduced visual acuity and increased sensitivity to light.
What is the difference between color blindness and red-green vision deficiency?? | Image: Renato Abati / pexels.com
Red-green vision deficiency test (eye test)
How to diagnose a red-green defect?
If red-green deficiency is suspected, a test can provide information. On so-called Ishihara charts, numbers or the like are shown with circles, which are hidden in a background also made of circles. The colors of the circles of number and background differ in hue, but not in brightness and saturation. The red and green shades of the circles are chosen so that someone with red-green deficiency cannot see the number. A person with normal vision, on the other hand, is.
Even more accurate is the Farnsworth test. Here the person concerned is supposed to sort color plates according to the hue. On the basis of the sorting it can be deduced from which type of color blindness the person is affected.
In addition, there are other tests that work in a similar way. Likewise a Red-green blindness with a so-called Ishihara color chart eye test (below).
Color blindness test: Ishihara color chart 45 (normal vision) or nothing (red-green vision deficiency) | Image: Science Museum, London*
Color blindness test: Ishihara color chart 74 (normal vision), 71 or nothing (red-green vision deficiency) | Image: Science Museum, London*
Causes of red-green vision defects
In the case of red-green weakness or red-green blindness, the cause is to be found in the genes. The genes for the visual pigments of the red and green cones are located on the X chromosome. If one of these genes is defective, women have a substitute for the defective gene with the genes of their second X chromosome. Since men have only one X chromosome, there is no substitute available to you. Because on the Y chromosome of men these genes are missing. Only when the replacement gene of the second X chromosome is also defective does red-green deficiency develop in women. In the case of red-green deficiency and red-green blindness, the inheritance is thus responsible for the fact that significantly more men than women are affected are. This means that Men About 11 times more often of of a Red-green vision impairment affects more people than women. About 9% of men and only ca. 0.8 % of all women suffer from this particular form of Color blindness.
Symptoms of red-green deficiency
People affected by red-green vision loss perceive fewer color tones than people with normal vision. Depending on whether red-blindness or green-blindness is present, the affected person sees red or green more weakly. This makes it more difficult for them to distinguish between the two colors. Blue and yellow tones can be seen without problems if there is no red or green mixed in. However, red-green deficiency can vary in severity. While to some the world appears almost as colorful as to normal-sighted people, others have far greater difficulties. In red-green blindness, the symptoms are so pronounced that the affected person cannot see red or green at all.
How to see with a red-green deficiency
Depending on the type and severity of color vision deficiency, sufferers may see some red things as green or vice versa. In more severe cases or true red-green blindness, red or green things appear brownish or gray instead.
Comparison of normal vision (left) and red-green deficiency (right) | Image: Christopher Alvarenga / unsplash.com
How severe red-green blindness can be?
Red-green blindness is so severe that the affected person is actually blind to either red or green. In rare cases, those affected can even see neither green nor red if both cone types are missing. A red-green deficiency, on the other hand, can vary in severity. Some hardly notice it, while in others it is almost as severe as red-green blindness.
What to do in case of red-green blindness?
If red-green deficiency is suspected, it is a good idea to have the degree of severity determined by an ophthalmologist at some point. Finally, it is only possible to a limited extent to estimate the full extent themselves. Often, only a few limitations in everyday life appear, which the affected persons have already mastered throughout their lives anyway. However, if it is more severe or red-green blindness is present, it can cause more significant problems in road traffic. For example, in foggy conditions, a person with red-green blindness can hardly or not at all recognize the taillight of the car in front. Similarly, he may perceive a red traffic light more difficult and later than a person with normal vision, especially at night. Those affected must be aware of this and, if necessary, leave driving in poor visibility to someone else.
Can red-green blindness be treated?
Red-green blindness is congenital. It does not change in the course of life. Therefore, in the case of red-green blindness, a Treatment not possible.
Only in the case of a red-green deficiency, special glasses may be able to provide slightly better color vision. For example, the company EnChroma has developed a Glasses Develops, which filters out certain wavelengths of light. This is to separate the signals of the different colors more clearly from each other, so that it should be easier for the brain to distinguish between red and green. Some people experience an improved color impression with EnChroma glasses. However, it does not correspond to the color vision of a person with normal vision. How well the glasses work also depends on the light conditions and the severity of the color vision deficiency.
Correct contact lenses for red-green deficiency
ChromaGen contact lenses are available, which contain a color filter similar to the EnChroma glasses. These can subjectively improve the color vision of some affected persons and possibly make everyday life somewhat easier. A contact lens expert specializing in this area adapts the contact lenses to the respective visual impairment. The contact lenses are also available with different diopter values.
However, a complete correction of a red-green weakness with these lenses is no more possible than with glasses. Whether and how well the lenses work varies from individual to individual. In any case, these contact lenses cannot help with complete red-green blindness.
Red-green visual impairment in children
Red-green vision impairment is congenital and therefore already present as a child. From school age at the latest it makes sense to know about it. For children, there are simpler color vision tests that show symbols or figures instead of numbers or letters. They are suitable for children from the age of three. Unlike defective vision, however, an undetected red-green defect does not have serious consequences that lead to a permanent visual defect.
Further information: Online eye test for children (incl. color vision test)