Color blindness, color vision deficiency, Color blindness Cure The reasons, color vision deficiencies

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Color blindness, or colour blindness, a color vision deficiency, is the inability to perceive differences between some of the colors that others can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or exposure to certain chemicals. The English chemist John Dalton published the first scientific paper on the subject in 1798, “Extraordinary facts relating to the vision of colours”,[1] after the realization of his own color blindness. Because of Dalton’s work, the condition was often called daltonism, although this term is now used for a type of color blindness called deuteranopia.

Color blindness is sometimes classed as a disability, however, in certain situations color blind individuals have an advantage over those with normal color vision. There are some studies which conclude that color blind individuals are better at penetrating certain color camouflages and it has been suggested that this may be the evolutionary explanation for the surprisingly high frequency of congenital red-green colour blindness.

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The words ‘colour blindness’ are misleading. People who cannot see all colours are not ‘blind’ – they can see things as clearly as people who are not ‘colour blind’. Colour blindness means that a person cannot ‘see’ some colours, or sees them differently from other people. Very few people who are colour blind are ‘blind’ to all colours. The usual colours which they see differently are greens, yellows, oranges and reds.

It can be worth knowing if a child is colour blind because he may have difficulty at school, especially in the early years when many activities use colours, such as drawing and sorting blocks. Using a computer can be a problem too for someone who is colour blind.

When children know colours
All of the cells and nerve pathways in the eye and the brain are present from birth, and very young children can see the difference between colours if they are not colour blind. They do not see colours very well at first but soon begin to like colours, especially bright colours.
However children under about 4 years may not understand that the ‘green’ of a ball, for example, is the same colour as the ‘green’ of grass.
The child needs more understanding of things like colours, shapes and sizes to ‘see’ that different things can be the same colour.
Younger children may be able to say that the ball is green, but not able to say that grass is also green (they know that it doesn’t look anything like the ball, and are confused when we want them to say the same describing word!).
Many children are able to recognise and name colours by the time they are 4.

What is colour blindness?
In the retina at the back of the eye (the part of the eye that picks up light coming in) there are two types of cells, ‘rod cells’ and ‘cone cells’, and these react differently to light.
Rod cells are very sensitive to light, and they can react to even very faint light such as light from a star in a hazy night sky, but they do not ‘see’ different colours. Using rod cells we can see things around us at night, but only in shades of black, grey and white.
Cone cells react to brighter light, and they help us to see the detail in objects. They also pick up colours.
There are three types of cone cells, ones that pick up red light, others green and others blue.
By combining the messages from each set of cone cells, we get the wide range of colours that we can normally see.
Someone who is colour blind lacks one or more of these types of cone cells.

What colorblindness is:

Color blindness (color vision deficiency) is a condition in which certain colors cannot be distinguished, and is most commonly due to an inherited condition. Red/Green color blindness is by far the most common form, about 99%, and causes problems in distinguishing reds and greens. Another color deficiency Blue/Yellow also exists, but is rare and there is no commonly available test for it.
Depending on just which figures you believe, color blindness seems to occur in about 8% – 12% of males of European origin and about one-half of 1% of females. I did not find any figures for frequency in other races. Total color blindness (seeing in only shades of gray) is extremely rare.
There is no treatment for color blindness, nor is it usually the cause of any significant disability. However, it can be very frustrating for individuals affected by it. Those who are not color blind seem to have the misconception that color blindness means that a color blind person sees only in black and white or shades of gray. While this sort of condition is possible, it is extremely rare. Being color blind does keep one from performing certain jobs and makes others difficult.

Life’s minor frustrations (and occasional dangers) for the color blind:

Weather forecasts – especially the Weather Channel – where certain colors just can not be distinguished on their weather maps. Also, maps in general because of the color coding on the legends.
Bi-color and tri-color LEDs (Light Emitting Diodes): Is that glowing indicator light red, yellow, or green?
Traffic lights, and worst of all, Caution lights: Color blind people always know the position of the colors on the traffic light – in most states, Red on top, Yellow in the center, Green (or is that blue?) on the bottom. It isn’t good when we go to a city or state where they put traffic lights horizontal – it takes a couple of days to get used to that one! But caution lights present an entirely different problem. In this situation there is only one light; no top or bottom, no right or left, just one light that is either red or yellow – but which is it?
Getting in the sun with your girlfriend: So, you’re out in the boat or on the beach with your girlfriend and soaking up the rays. But I can’t tell until far too late if I’m getting red – or if she is. If I can tell it’s red, by that time it’s fire engine red and a painful sunburn is already present.
Color observation by others: “Look at those lovely pink flowers on that shrub”. My reply, looking at a greenish shrub “What flowers?”
Purchasing clothing: I’ve got some really neat colors of clothes. Not everyone appreciates them like I do though; they seem to think the colors are strange. I just don’t know why!
Kids and crayons: Color vision deficiencies bother affected children from the earliest years. At school, coloring can become a difficulty when one has to take the blue crayon -and not the pink one- to color the ocean.
Test strips for hard water, pH, swimming pools, etc.: A color blind person is generally unable to :
interpret some chemical reactions
see that litmus paper turns red by acid
identify a material by the color of its flame such as lead blue or potassium purple
interpret the chemical testing kits for swimming pool water, test strips for hard water, soil or water pH tests – all of which rely on subtle color differences and a band of similar colors to compare against.
Cooking and foods:
When cooking, red deficient individuals cannot tell whether their piece of meat is raw or well done. Many can not tell the difference between green and ripe tomatoes or between ketchup and chocolate syrup.
Some food can even look definitely disgusting to color deficient individuals. For example, people with a green deficiency cannot possibly eat spinach which to them just look like cow pat. They can however distinguish some citrus fruits. Oranges seem to be of a brighter yellow than that of lemons.
Are you wearing lipstick? Many color blind people cannot tell whether a woman is wearing lipstick or not. More difficult to handle for some is the inability to make the difference between a blue-eyed blonde and a green-eyed redhead.

Clinical information about color blindness:

Cones (color sensitive receptors) containing single visual pigments selective for red, green, and blue light, are present in the normal human eye. Disturbances of color vision will occur if the amount of pigment per cone is reduced or if one or more of the three cone systems are absent.
Although defective color vision may be acquired as a result of another eye disorder, the vast majority of color blind cases are hereditary – present at birth. The gene for this is carried in the X chromosome. Since males have an X-Y pairing and females have X-X, color blindness can occur much more easily in males and is typically passed to them by their mothers.
Color blindness is rooted in the chromosomal differences between males and females. Females may be carriers of color blindness, but males are more commonly affected.
Color blindness is a malfunction of the retina, which converts light energy into electircal energy that is then transmitted to the brain. This conversion is accomplished by two types of photoreceptor cells in the retina: rods and cones.
The cones are responsible for encoding color. Each cone contains structures or visual pigments sensitive to one of three wavelengths of light: red, green, and blue. Normal persons are able to match all colors of the spectrum by mixtures of only three fundamental color sensitivities. Hence, the huge variety of colors we perceive stems from the cone cells’ response to different compositions of wavelengths of light.
Defects in color vision occur when one of the three cone cell color coding structures fails to function properly. One of the visual pigments may be present and functioning abnormally, or it may be absent altogether.
For practical purposes, all color-deficient individuals have varieties of red or green deficiency. Blue deficiencies are very rare. Color deficient patients are not completely red or green blind. Compared to persons with normal color vision, they have some trouble differentiating between certain colors, but the severity of the color deficiency is variable.
Color blindness is normally diagnosed through clinical testing. (See the Ishihara color test – the one most common test used) Although there is no treatment for color blindness, most color deficient persons compensate well for their defect and may even discover instances in which they can discern details and images that would escape normal-sighted persons. At one time the U.S. Army found that color blind persons can spot “camouflage” colors where those with normal color vision are fooled by it.

How color blindness works:

The human eye sees by light stimulating the retina (a neuro-membrane lining the inside back of the eye). The retina is made up of what are called Rods and Cones. The rods, located in the peripheral retina, give us our night vision, but can not distinguish color. Cones, located in the center of the retina (called the macula), are not much good at night but do let us perceive color during daylight conditions.
Many people think anyone labeled as “colorblind” only sees black and white – like watching a black and white movie or television. This is a big misconception and not true. It is extremely rare to be totally color blind. There are many different types and degrees of colorblindness, really they are “color deficiencies” since virtually no one is truly blind to all colors.
People with normal cones and color vision are able to see all the different colors and subtle mixtures of them by using cones sensitive to one of three wavelength of light – red, green, and blue.
A mild color deficiency is present when one or more of the three cones functions “poorly”. A more severe color deficiency is present when one of the cones does not function at “all” or is missing.
Protanomaly (one out of 100 males):
Protanomaly is referred to as “red-weakness”, an apt description of this form of color deficiency. Any redness seen in a color by a normal observer is seen more weakly by the protanomalous viewer, both in terms of its “coloring power” (saturation, or depth of color) and its brightness. Red, orange, yellow, yellow-green, and green, appear somewhat shifted in hue (“hue” is just another word for “color”) towards green, and all appear paler than they do to the normal observer. The redness component that a normal observer sees in a violet or lavender color is so weakened for the protanomalous observer that he may fail to detect it, and therefore sees only the blue component. Hence, to him the color that normals call “violet” may look only like another shade of blue.
Under poor viewing conditions, such as when driving in dazzling sunlight or in rainy or foggy weather, it is easily possible for protanomalous individuals to mistake a blinking red traffic light from a blinking yellow or amber one, or to fail to distinguish a green traffic light from the various “white” lights in store fronts, signs, and street lights that line our streets. Do not let them adjust the color on the television, because it will look far to redish or violet for the rest of the family members.
Deuteranomaly (five out of 100 of males):
Let the deuteranomalous person adjust your television and he would add more green and subtract red. He is considered “green weak”. Similar to the protanomalous person, he is poor at discriminating small differences in hues in the red, orange, yellow, green region of the spectrum. He makes errors in the naming of hues in this region because they appear somewhat shifted towards red for him – difficulty in distinguishing violet from blue.
From a practical stand point though, many protanomalous and deuteranomalous people breeze through life with very little difficulty doing tasks that require normal color vision. Some may not even be aware that their color perception is in any way different from normal. The only problem they have is passing a color vision test.
Dicromasy – can be divided into protanopia and deuteranopia (two out of 100 males):
These individuals normally know they have a color vision problem and it can effect their lives on a daily basis. They see no perceptible difference between red, orange, yellow, and green. All these colors that seem so different to the normal viewer appear to be the same color for this two percent of the population.
Protanopia (one out of 100 males):
For the protanope, the brightness of red, orange, and yellow is much reduced compared to normal. This dimming can be so pronounced that reds may be confused with black or dark gray, and red traffic lights may appear to be extinguished. They may learn to distinguish reds from yellows and from greens primarily on the basis of their apparent brightness or lightness, not on any perceptible hue difference. Violet, lavender, and purple are indistinguishable from various shades of blue because their reddish components are so dimmed as to be invisible e.g. Pink flowers, reflecting both red light and blue light, may appear just blue to the protanope.
Deuteranopia (one out of 100 males):
The deuteranope suffers the same hue discrimination problems as the protanope, but without the abnormal dimming. The names red, orange, yellow, and green really mean very little to him aside from being different names that every one else around him seems to be able to agree on. Similarly, violet, lavender, purple, and blue, seem to be too many names to use logically for hues that all look alike to him.

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