The most common form of color blindness is the inability to distinguish red and green. Fortunately, complete color blindness is rare. Those affected are only able to distinguish various shades of gray. The condition is hereditary. Eyeglasses and contact lenses don't help, but here is some useful information.
Most people take the ability to see life in bright colors for granted. They make sure the colors of their clothing match, feel hungry at the sight of a delicious red strawberry and enjoy all the colors of nature. But for some 180 million people around the world, this experience of color remains partially or completely out of reach – they either have red-green color deficiency or blindness, have greatly reduced color vision, or in very rare cases, cannot distinguish any colors at all. This is colloquially known as color blindness.
In people with normal color vision, the three spectral colors red, green and blue are mixed to create all other colors. This process is carried out by sensory cells on the retina called “cones.” The cones work only during the day: at night we actually see everything in shades of gray. However, not all color blindness is the same. Even though everyone thinks it's the same thing, the term covers many different defects. Experts distinguish the following conditions:
Those affected have only a limited ability to recognize certain shades. All the sensory cells – the red, green and blue cones – are present in the retina, but some of them work incorrectly, usually the cones responsible for seeing green. The technical term is deuteranomaly. People with a red deficiency are said by doctors to have protanomaly.
In this type of color blindness, some of the sensory cells are missing. People affected have only two functioning cone types. The result is that their color vision is significantly reduced. This can sometimes be dangerous - especially for red-weak and red-blind car drivers. In fog, for example, they see only black instead of the red rear light of a vehicle in front of them.
The disorder known as achromatopsia is very rare. People with this condition cannot perceive shades of color at all. They are also very sensitive to light. They are always in "night mode" and can only perceive rough outlines in the dark.
Both congenital color blindness and innate color visual deficiency are caused by a genetic defect. It is much more common among men than women. The most frequently occurring color vision defect is limited blue-yellow vision. It often occurs as a result of macular degeneration. People who have been unable to see certain colors since birth, or who see colors only poorly are often unaware of it. The problem is detected only when their environment brings it to their attention.
Color blindness can be diagnosed through different color tests, which is important because problems can occur both in work and when driving. The following tests are possible:
This test shows numbers on a colored background (often resolved into dots). It can be used to detect red-green color blindness.
Farnsworth colored dot procedure
Here, patients sort stones of different hues. The test is somewhat more complicated. It can be used to detect a blue deficiency.
Here, the patient uses a circular color testing device to mix and specify the shades of varying colors. Thus, information concerning the degree of color blindness can be obtained. This is the best method for diagnosing red blindness. It can be an exclusion criterion for some professions, such as painter, bus driver and pilot.
So far, it is not possible to correct color blindness using eyeglasses or contact lenses. Special glasses are available that can change the color contrast, but they cannot correct the wearer’s vision. Nevertheless, here is a useful tip for people who are totally color-blind: special glasses with red lenses that deflect the glare of daylight better than normal glasses or sunglasses.