Color Blindness


How do we see color?


Color is a sensation that is aroused when light passes through the eye and falls on special cells of the central part of the retina.  These cells are called cones and they contain light sensitive chemicals, which interact with light.  In the normal subject these cones can accurately distinguish red, blue and green and these colors can be further blended to help perceive all other colors of the spectrum. However, if the cones lack one or more of these light sensitive chemicals the ability of that person’s perception of certain colors will be disturbed.


What is color blindness?


Color blindness is the inability to recognize the colors red, green, blue or any combination of these.


How does a color blind person see the world?


People with color blindness either are unable to distinguish between certain shades of color or find certain colors muted and less discernible.  Only in extreme rare cases is everything seen in shades of gray.  The most common color deficiency is the inability to see red and green.  These shades may be perceived as neutral or gray. Defects may be mild, moderate or severe depending on the amount of light sensitive chemicals, which are missing from the cones. Most affected individuals however, are unaware of the problem.  For example, they will call a rose red and the leaves green even if their “green” is what a normal person would call yellow. But since they have always heard that leaves are green they interpret what they see as green.


What are the causes of color blindness?


Hereditary: Color blindness is almost always an inherited disorder caused by a defective gene that is passed from a mother to her son. About 8% of all men, but less than 0.5% of all women are color blind because females usually possess genes that counteract the deficiency. Affected individuals usually have difficulty in accurately perceiving red and green which can be mild, moderate or severe depending on the severity of the genetic defect. If you inherit any degree of color deficiency it remains stable throughout life. Your ability to see however is normal.


Acquired:  Acquired color deficiency represents less than 2% of total color deficiencies. They can be caused by certain diseases or injuries of the retina or the optic nerve (the nerve that transmits visual signals to your brain) or by certain medications. A person with acquired color blindness may find it difficult to recognize colors the way he once did.  Acquired diseases usually affect the perception of red and green color. Acquired color deficiencies worsen if the disease, which causes them, worsens. They can also get better if the disease gets better. Cataracts can also obstruct color perception, but usually color vision returns to normal once the cataract is removed by surgery. Color vision can also deteriorate as a normal part of aging.


How serious is color blindness?


Hereditary color deficiencies are in reality more inconvenient than dangerous. Whatever the degree of the deficiency you inherit, the defect remains stable throughout life. Visual acuity is normal, and apart from taking certain precautions such as paying special attention in determining traffic signals for example, or refraining from practicing certain occupations that are impractical for color deficient such as piloting or designing. A color deficient person usually leads a normal life.





Is there a treatment for color blindness?


Hereditary color deficiencies have no cure at this time. Acquired color deficiencies however, may improve if the course of the disease, which caused them, can be slowed or reversed with treatment.


Diagnosis of color blindness


If you have trouble seeing certain colors, check with your doctor who can quickly and easily perform simple and quick tests to see if you have color deficiency. He or she can find out the type of color deficiency you have and make sure that you have no associated eye disease, which requires treatment.

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