Color Blindness, or Color Vision Deficiency, is an eye condition where a person is not able to differentiate certain colors or shades of colors to some degree. It is most often genetic in nature, but may also take place due to eye, nerve, or brain injury, or exposure to certain chemicals, damage to the retina and macula, and aging or when the lens is darkened over time from a cataract. The English chemist John Dalton published the first scientific paper on the subject in 1798, “Extraordinary facts relating to the vision of colors”, after the recognizing his own color blindness. Because of Dalton’s work, the condition was often termed as daltonism. Now this term is used for a type of color blindness called deuteranopia.
There are 3 main kinds of color vision defects among which Red-green color vision defects are the most widespread. This type is more common with men than with women. The other major types include blue-yellow color vision defects and a complete absence of color vision.
A color blind person can see different colors; but they are not able to see some specific colors due to deficiencies in the eyes. Although there is hardly any absolute treatment for hereditary color blindness, there are methods, techniques, and special glasses that may help people with color blindness differentiate between colors but not truly see them.
What causes Color Blindness?
The retina containing rods and cones help us to view objects in various colors and varying degrees of brightness. The cones are regarded as photoreceptors that allow us to differentiate between many colors and diverse shades of these colors too. The cones containing light sensitive pigments are specific to range of wavelengths. There are three different kinds of cones having one sensitive to short wavelengths, or the color blue, another sensitive to medium wavelengths, or the color green, and the other sensitive to higher wavelengths, or the color red. When deficiencies occur in the cones, either at birth or acquired through other means, the cones can’t distinguish the specific wavelengths and this results in different perspective of a color range. Lack of the cones responsible for green and red hues can also interfere with the sensitivity to brightness. Color blindness is hereditary and thus it is generally passed on during birth. As we grow up our sensitivity decreases too but usually not alarmingly. Damage to the retina due to eye diseases or physical disorders may also cause color blindness.
Risk factors
Inherited disorder: About one in 12 males of Northern European origin acquire some degree of red-green color deficiency by birth. Most females have genes that counter this visual deficiency, and less than 1% of females of Northern European descent possess this sort of color deficiency. In other countries, the predominance of red-green color deficiency is not so widespread.
Blue: yellow color deficiency is acquired by fewer than 1 in 10,000 people throughout the world, and absolutely inherited colorblindness affects fewer than 1 in 30,000 people. You may inheritance of the disorder ranges from mild, moderate to severe degree, and the severity doesn’t alter over your lifetime if the cause is genetic.
Diseases: Some conditions that can bring about color deficits are diabetes, glaucoma, macular degeneration, Alzheimer’s disease, Parkinson’s disease, chronic alcoholism, leukemia and sickle cell anemia. One eye may be more damaged than the other and may gradually recover if the primary cause of the disease can be treated.
Certain medications: Some medications can affect color vision, for examples some drugs prescribed to treat heart diseases, high blood pressure, infections, nervous breakdowns and psychological problems.
Aging: As you age the ability to differentiate colors gradually deteriorates.
Chemicals: Exposure to some strong chemicals in the workplace, such as carbon disulfide, fertilizers and styrene may cause loss of color vision. If you work around these chemicals, evaluate your color vision because the loss of some color vision may be so slight for you that it can’t be noticed
Types of Color Blindness
Color blindness can be categorized as acquired or inherited.
There are 3 types of inherited or inborn color vision deficiencies: monochromacy, dichromacy, and anomalous trichromacy.
Monochromacy: It is also known as “total color blindness” – the complete lack of ability to distinguish colors; caused by cone defect or absence of cone. Monochromacy takes place when 2 or all 3 of the cone pigments are absent and color and brightness vision is reduced to one dimension.
Rod monochromacy (achromatopsia): It is an exceptionally rare, nonprogressive inability to identify any colors. Such condition happens as a result of absent or inactive retinal cones. It is linked with light sensitivity (photophobia), spontaneous eye oscillations (nystagmus), and reduced vision.
Cone monochromacy: It is the condition of possessing both rods and cones, but only a particular type of cone. A cone monochromat may possess good pattern vision at normal daylight levels, but will not be able to differentiate colors. It is a rare type of complete color blindness.
Dichromacy: It is a fairly serious color vision deficiency in which one of the 3 basic color mechanisms is missing or not working. It is genetic in nature and, in the case of Protanopia or Deuteranopia, it predominantly affects males. Dichromacy is a result of the absence of one of the cone pigments and reduction of colors to two dimensions.
Those having this type of deficiency are normally aware of their color vision problem and it can influence their lives badly on a daily basis. They see no noticeable difference between red, orange, yellow, and green. All these colors that appear so different to the normal viewer seem similar to this 2 % of the population.
Protanopia – In this type shades of red are considerably reduced, if present in any way, in depth and brightness. It is inherited, sex-linked, and is seen in 1% of males. Violet, lavender, and purple are impossible to differentiate from various shades of blue because their reddish components are so dimmed as to be nearly invisible. For instance, Pink flowers that reflect both red light and blue light may seem just blue to the protanope. For the protanope, the brightness of red, orange, and yellow is much less in comparison to normal. This dimming can be so distinct that reds may be confused with black or dark gray, and red traffic lights may appear to be extinguished. They may know how to differentiate reds from yellows and from greens primarily depending upon their visible brightness or lightness, not on any perceptible hue difference.
Deuteranopia: In this type the shades of green appear greatly reduced, if present at all, in depth and brightness. It is a form of dichromatism in which there are only 2 cone pigments present. It is also hereditary and connected with sex. The names red, orange, yellow, and green really matter very little to him apart from being different names that every one else around him believes.
Tritanopia: It is a very uncommon condition where shades of blue are greatly reduced, if present at all, in depth and brightness. In case of tritanopia only two cone pigments remain along with a total absence of blue retinal receptors.
Anomalous trichromacy: it is a common hereditary color vision disorder, which take place when one of the 3 cone pigments is altered in its spectral sensitivity. This causes an impairment, rather than loss of trichromacy (normal 3-dimensional color vision).
Protanomaly: It is a mild color vision defect in which an altered spectral sensitivity of red retinal receptors (nearer to green receptor response) causes poor sense of discrimination between red-green hues. It is genetic, sex-linked, and present in 1% of males.
Deuteranomaly: It is caused by a similar change in the green retinal receptors. It is by far the most common type of color vision deficiency, slightly affecting red-green hue discrimination in 5% of males. It is hereditary and linked with sex.
Tritanomaly: It is a rare kind of hereditary color vision deficiency influencing blue-yellow hue discrimination. Contrasting most other forms, it is not sex-linked.
Diagnosis
The Ishihara color test, consisting of a series of pictures of colored spots, is most often used to identify red-green color deficiencies. A figure (usually one or more Arabic digits) is embedded in the picture just like a number of spots in somewhat different color, and can be visible with normal color vision, but not with a particular color defect. The full set of tests consists of a variety of figure/background color combinations, and makes diagnosis possible of which specific visual defect is present. The anomaloscopeis is also used in diagnosing anomalous trichromacy.
Ishihara color test contains only numerals. Therefore it may not be useful in diagnosing young children, who are yet to learn use numerals. For the sake of identifying these problems early on in life, optional color vision tests were developed using only symbols (square, circle, and car).
Most clinical tests are developed to be fast, simple, and useful in identifying wide categories of color blindness. On the other hand, in academic studies of color blindness, more interest is laid on developing easy tests in order to collect detailed datasets, identify copunctal points, and gauge just obvious differences.
Management
There is normally no such treatment to treat color blindness. However, certain types of painted filters and contact lenses may help an individual to improve distinguish different colors. Optometrists can provide a special red-tint contact lens to wear on the non-dominant eye.
This may enable one to pass some color blindness tests, but in reality they have slight practical use. The effect of wearing such a device is similar to wearing red/blue 3D glasses and can need some time getting used to as certain wavelengths can swoop and be overly represented. Additionally, computer software and cybernetic devices have been formulated to help those with visual color difficulties like an eyeborg, a “cybernetic eye” that allows individuals with color blindness to listen to sounds representing colors.
The GNOME desktop environment offers colorblind accessibility using the gnome-mag and the libcolorblind software. Using a gnome applet, the user may shift a color filter on and off selecting from a set of probable color transformations that will dislocate the colors to establish them. The software enables a color blind to view the numbers in the ishihara test.
In September 2009, the journal “Nature” revealed that researchers at the University of Washington and University of Florida were successful to provide trichromatic vision to squirrel monkeys, which normally possess only dichromatic vision, using gene therapy