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| Each cone interprets only one color-red,
green or blue. |
Overview
Color blindness, also known as color vision deficiency,
is the inability to distinguish colors and shades or to
recognize them at all. It occurs when the color-sensing
cones of the retina are absent or do not function
properly.
About 8 percent of males and 1 percent of females are
color-blind to some degree. Most color-blind people have
difficulty in distinguishing among various shades of the
same color or seeing some colors as brightly as others;
the inability to distinguish any colors at all and see
the world in black-and-white is rare.
Most color blindness is inherited and present at
birth. But acquired color blindness can result from
cataracts, retinal or optical nerve disease, use of
certain medications or simply the normal aging process
-- as we age, the normally clear lens begins to darken,
making it harder to differentiate one dark color from
another.
Normally, the pigments of each cone correspond to one
of the primary colors of light – red, blue and green. In
color blindness, there is a broad range of variances in
these cones, including unbalanced proportions of cones
for each color, absence of cones for one or more colors,
and malfunction of cones for one or more colors. If no
functioning cones are present, the rods take over in
sensing lightness and darkness that enhance peripheral
vision and vision in dim light.
Symptoms
While people with color blindness may have trouble
distinguishing any or various colors or shades, the most
common inherited form is “red/green” color blindness, in
which there are problems seeing shades of red or green.
For instance, red might appear as yellow or invisible or
that pastel shades of yellow and green are
indistinguishable. Another common form is blue/yellow
color blindness.
Prevention
Color blindness is usually detected during a routine eye
exam. Children should be tested for color blindness
beginning at age 4. It cannot be prevented, but poses no
threat to overall health. Although it may be
inconvenience to some people, it presents no handicap on
everyday life.
Treatment
While color blindness cannot be cured, there are many
methods of coping with and compensating for the
difficulties it presents, such as:
- Tinted contact lenses can make some
colors appear dimmer or brighter, and may help some
with certain color vision deficiencies. Some
color-blind people claim that wearing a lens in one
eye helps their vision and functioning, although
there is no evidence indicating that the lenses
actually allow them to see more colors. The lenses
may blur vision and distort depth perception,
creating potentially dangerous situations.
- Electronic Eyes are hand-held devices
that identify colors. In such devices, color sensors
activate an audio synthesizer that speaks the color
aloud. The sensors, however, cannot read text.
If your child is color-blind, you can make
modifications to help him/her identify colors. This
includes activities such as labeling clothing,
accessories and other items to help with coordination,
and teaching how to recognize brightness and location of
green, yellow and red positions on traffic lights and
the meaning of signs by shape. You may also have to make
adjustments in reading materials at school. Be on alert
for books that use colored print and colored backgrounds
and inform teachers that color-oriented and color-coded
school assignments are not appropriate for your child. |
