Color blindness is a vision problem that makes it hard to
tell the difference between certain colors. If you are
color blind, it usually does not mean you see everything in
black and white or shades of gray. Full color blindness is
very rare. Most color-blind people have trouble with just 1
or 2 colors. The colors they have the most difficulty
telling the difference between are red and green. Shades of
red and green might look brownish to a color-blind person.
How does it occur?
You see in color because the retina at the back of the eye
has special cells called cones. There are 3 types of cones:
cones for red light, cones for green light, and cones for
blue light. These 3 types of cones mix the colors together
to create all of the colors people see. In a color-blind
person, the red and green cones are very similar to each
other so that it is difficult to tell the difference between
red and green colors. This causes an abnormal mix of color
and color confusion.
Color blindness is usually an inherited and lifelong
condition. It is most commonly passed from mother to son.
A woman can be a "carrier" of the gene but will usually not
be color blind herself. Men cannot be just carriers of
the gene. If a man has the color blindness gene then he is
color blind. For that reason, men are more commonly color
blind than women.
Rarely an eye disease can cause you to become color blind
later in life. Usually color blindness is not caused by a
disease.
How is it diagnosed?
Your eye doctor can do a very simple test for color
blindness. You look at a special test book that has a
pattern of small colored circles. Some of the circles on
the page are a different color and form a number. A color
blind person will not be able to see the number because it
will appear as the same color as the other circles on the
page. The test book has about a dozen of these patterns in
it to make sure of the diagnosis and to judge the severity
of the color blindness. This test is usually easy enough
that it is possible to get good results even with young
children.
How is it treated?
Usually there is no need to treat color blindness. People
with color blindness learn to tell the differences between
colors. For example, green might look brighter than red.
If a person is severely color blind, occasionally a red
tinted contact lens is prescribed for just one eye. This
may help the person see colors a little better.
How can I take care of myself?
Usually nothing needs to be done. You many find that some
tasks are frustrating such as:
- judging traffic lights
- reading test strips or identifying other chemical
reactions
- coloring with markers or crayons
- matching clothes
- reading color-coded maps or weather charts
- knowing if fruits are ripe or if meat is rare or
well-done.
In some cases, a color blind person may need to avoid
careers that require excellent color vision. However, there
are many color blind electricians who can easily work with
multi-colored wires. Most of the time you can learn to
adjust by using other cues such as looking for the position
of the light on a traffic signal rather than the color or
looking for subtle color differences (red may appear darker
than green). Parents may need to give their color blind
child more assistance picking out clothes until the child
can learn how to match colors.
Reviewed and approved by the Wilmer Eye Institute of The Johns Hopkins
Medical Institutions, Baltimore, MD. Web site: http://www.wilmer.jhu.edu
Disclaimer: This content is reviewed periodically and is subject to
change as new health information becomes available. The
information provided is intended to be informative and educational and is not a
replacement for professional medical evaluation, advice, diagnosis or
treatment by a healthcare professional.
HIA File eye4202.HTM Release 9.0/2006. Copyright © 2006 McKesson Corporation and/or one of its subdiaries. All Rights Reserved.
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