Red stands for love, the romantic pink tranquilizes, blue represents loyalty while purple represents royalty. Green soothes your mind while yellow can make you lose your temper! Every color has a meaning. But the significance of colors is apparent to only those who can see them. Color blindness is the inability to perceive the differences in colors. This is a deficiency seen in humans, wherein one is unable to distinguish between certain colors. It is mostly genetic or may be caused due to impairment in the eye, brain, or due to nerve damage. The English chemist John Dalton realized that he was colorblind. He, for the first time in 1798, published about color blindness in his paper titled, 'Extraordinary facts relating to the vision of colors'. Color blindness is also referred to as Daltonism.
The Human Eye
Human retina is the inner layer of the eye, which is sensitive to light. It contains two kinds of light cells namely rods and cones. Rod cells are active in less light whereas cone cells act during normal light. There are three types of cones, each containing a distinct pigment. Each of the three types of cones is responsible for perception of one of the colors red, green or blue. Different colors are perceived when different types of cones are stimulated to different extents. The three types of cones have gifted us trichromatic vision. We are trichromats.
- Causes of color blindness arise from about 19 chromosomes and many different genes. Genes responsible for color vision are mostly found on the X chromosome. Hence color blindness is more common in men than in women.
- Inherited color blindness can be congenital or acquired in childhood or adulthood. Color blindness can be stationary or progressive. In cases of acute color blindness, the person might eventually become completely blind.
- Shaken baby syndrome is another important cause of color blindness. This happens in case of damage to the child's retina and brain. Accidents might harm the retina or the brain leading to color blindness.
- Exposure to UV radiation may damage the retina, causing color blindness. This is the main cause of color blindness in children. The color vision deficit stays with them for life.
Color blindness can either be an inherited deficiency or an acquired one. Inherited color blindness is due to genetic disorders in the photoreceptor cells. They result from the malfunction of different types of cone cells. Often, one is unable to distinguish between the colors yellow, red, and green. Another type of color blindness is the problem in differentiating between blue and yellow. The rarest type of colorblindness is monochromacy, which leaves the world black and white for those with the condition. Acquired color blindness is not necessarily irreversible. In case of the acquired type, only a part of one's visual field may be color blinded. Monochromacy is seen in two different forms namely Rod monochromacy and Cone monochromacy. Dichromacy is a type of color blindness, wherein a person relates any color he/she sees, to some mixture of only two spectral lights. Protanopia, Deuteranopia and Tritanopia are forms of Dichromacy.
- Rod monochromacy: Retina does not contain cone cells. People with rod monochromacy face problems in seeing normally during normal light intensities.
- Cone monochromacy: A person having only one kind of a cone is said to be a cone monochromat. A monochromat cannot distinguish between hues.
- Protanopia: Protanopes lack the retinal cones, which are sensitive to long wavelengths. They cannot discriminate colors in the green-yellow-red section. They perceive red, orange and yellow colors as less bright than they actually are. They lack the perception of hue difference in the reds, yellows and greens. The pinks can appear blue to protanopes.
- Deuteranopia: The problems faced by Deuteranopes are similar to those by Protanopes. The perception of diminished brightness is absent in these people. They are deficient of the medium wavelength sensitive cone cells.
- Tritanopia: Tritanopians are unable to differentiate between colors in the blue-yellow section.
Apart from these types, anomalous trichromacy manifests itself in forms of protanomaly, deuteranomaly, and tritanomaly. Protanomalous people can interpret red as black. Deuteranomalous people are less sensitive to the green side of the color spectrum. Individuals with tritanomaly lack the ability to differentiate between blue-yellow hues.
Identification and Treatment
Ishihara color test is a way to diagnose color blindness. A figure formed by dots of certain colors is depicted on a different colored background. The design is such that the figure will be identifiable only by those with normal color vision. Those with a disorder in perceiving colors cannot identify the object shown. Color tests are devised to be effective in broadly categorizing colorblind people.
Contact lenses and filters can assist colorblind people. Many types of computer software have been developed to help people with difficulties in perceiving color. There is no real remedy for color blindness. The National Eye Institute is trying to find one.
How does Color Blindness Affect You?
Colorblind people find it difficult to identify color codes. They face problems in reading maps with red and green coloration. Some colorblind people cannot identify the color of a thin line while they are able to recognize a color when it is present in greater amounts. Color of a relatively thicker line is recognizable. Those with an impaired color vision have problems in distinguishing signal lights and other red or green colored traffic signs.
In a Different Light
Camouflages do not deceive the eyes of a colorblind person. A colorblind hunter is more efficient at spotting an animal. Secondly, color blindness is one deficiency you can easily carry through your lives. It in no way stops you from leading a normal life. It is actually incorrect to call color blindness a disability. It can be taken as a different way of seeing things or a unique perception of colors.