The correct name for color blindness is color vision deficiency. Color vision deficiency is a term used to describe a number of different problems people have with color vision. These problems may range from a slight difficulty in telling different shades of a color apart to not being able to identify any color.
Most people with color vision deficiency can see colors, but they have difficulty differentiating between:
-particular shades of reds and greens (most common) or
-blues and yellows (less common).
The fact that color blindness is so much more prevalent among men implies that, like hemophilia, it is carried on the X chromosome, of which men have only one copy. (As in hemophilia, women are protected because they have two X chromosomes; a normal gene on one chromosome can often make up for a defective gene on the other).
People who are totally color blind, a condition called achromatopsia, can only see things as black and white or in shades of gray. But it is uncommon. People with achromatopsia almost always have additional problems with vision including reduced visual acuity, increased sensitivity to light (photophobia), and small involuntary eye movements called nystagmus.
Mutations in the CNGA3, CNGB3, GNAT2, OPN1LW, OPN1MW, and OPN1SW genes cause color vision deficiency.
To understand what causes color blindness, you need to know about the cones in your eyes. They are very small. These cones are cells on your retina, an area the size of a postage stamp that's at the back of your eye.
You have "red," "blue," and "green" cones, which are sensitive to those colors and combinations of them. You need all three types to see colors properly. When your cones don't work properly, or you don't have the right combination, your brain doesn't get the right message about which colors you're seeing. To someone who's color-blind, a green leaf might look tan or gray.
The most common form of color deficiency is red-green. This does not mean that people with this deficiency cannot see these colors at all; they simply have a harder time differentiating between them. The difficulty they have in correctly identifying them depends on how dark or light the colors are.
Another form of color deficiency is blue-yellow. This is a rarer and more severe form of color vision loss than red-green since persons with blue-yellow deficiency frequently have red-green blindness too. In both cases, it is common for people with color vision deficiency to see neutral or gray areas where a particular color should appear.
The severity of color vision deficiency can range from mild to severe depending on the cause. It will affect both eyes if it is inherited and usually just one if the cause for the deficiency is injury or illness.
Usually, color deficiency is an inherited condition caused by a common X-linked recessive gene, which is passed from a mother to her son. But disease or injury damaging the optic nerve or retina can also result in loss of color recognition. Some specific diseases that can cause color deficits are:
-diabetes
-glaucoma
-macular degeneration
-Alzheimer's disease
-Parkinson's disease
-multiple sclerosis
-chronic alcoholism
-leukemia
-sickle cell anemia
Other causes for color vision deficiency include:
-Medications : certain medications such as drugs used to treat heart problems, high blood pressure, infections, nervous disorders and psychological problems can affect color vision.
-Aging : the ability to see colors can gradually lessen with age.
-Chemical Exposure : contact with certain chemicals such as fertilizers and styrene have been known to cause loss of color vision.
Color deficiency can be diagnosed through a comprehensive eye examination. Testing will include the use of a series of specially designed pictures composed of colored dots, called pseudisochromatic plates, which include hidden numbers or embedded figures that can only be correctly seen by persons with normal color vision.
It is possible for a person to have poor color vision and not know it. Quite often, people with red-green deficiency aren't even aware of their problem since they've learned to see the "right" color. For example, tree leaves are green, so they call the color they see green. Also parents may not suspect the condition in their children until a situation causes confusion or misunderstanding. Early detection of color deficiency is vital since many learning materials rely heavily on color perception or color coding.
Unfortunately, there is no cure for hereditary color vision deficiency. If you have color vision deficiency, it is possible for you to learn to recognize color by other means. Some people learn to tell colors apart by brightness or location. Also, there are specially tinted eyeglasses that may help you to tell certain colors apart.
But if the cause is an illness or eye injury, treating these conditions may improve color vision.Though color vision deficiency can be a frustration and may limit participation in some occupations, in most cases it is not a serious threat to vision and can be adapted to your lifestyle with time, patience and practice.
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