Color Vision Deficiency
by Marianne Deal Stephens
Color Vision Deficiency, also called Colorblindness, affects 8% of boys and 0.5% of girls, or about 1 in 25 children. An affected child sees colors differently than most of his or her classmates or family members. Depending upon the type of Color Vision Deficiency, a child’s view may vary subtly or dramatically.
A child with Color Vision Deficiency may have difficulties when his or her perceptions clash with normal color perceptions. No medical treatment can cure the Color Vision Deficiency, but greater awareness of the condition can minimize any difficulties.
Possible Signs of Color Vision Deficiency
A child with a Color Vision Deficiency might:
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Give alternate names to colors, particularly non-primary shades.
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Draw with an alternate color scheme. The drawings might include green skin or hair, black tree trunks, or brown grass.
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Call things white that others call light pink or light green.
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Describe as similar some shades of reddish and greenish colors (i.e., peach and light green, or evergreen and cranberry).
In most cases, a child with Color Vision Deficiency has a maternal grandfather with the condition.
For a definitive diagnosis, see your eye care professional.
Testing
Some states and/ or school districts require color vision screening; your child may undergo testing at school, often in Kindergarten. School screenings alert parents and teachers that there may be a color perception issue, yet do not replace an examination by an eye care professional.
Your doctor will administer a color vision test by having the child view a set of diagrams called plates. Most plates have a number, letter, or symbol hidden in a circle of dots. The most common test is the Ishihara, though there are many others. After a child views and responds to a set of plates, the doctor will diagnose the particular type of Color Vision Deficiency.
Parents with normal color vision may be startled by watching their child take a test. Symbols that appear obvious to the parents may be undetectable to their child. Parents should remember that the carefully calibrated plates do not reproduce the everyday world.
Many online tests reproduce the Ishihara or other color vision tests. While these tests may be informative and convenient, they are not diagnostic tools.
Causes
Color Vision Deficiency runs in families, and is carried on the X chromosome. Males are XY, and females are XX.
A boy with Color Vision Deficiency inherited the affected X from his mother, who inherited it from her father, the boy’s grandfather. A woman who carries the gene usually has normal color vision. When she has children, she passes on either her affected X or her normal X chromosome. Her boys each have a 50% chance of inheriting the affected X, so each has a 50% chance of having Color Vision Deficiency. Since the Y from boys’ father does not alter the inheritance, boys have Color Vision Deficiency in far greater numbers than girls.
A girl with Color Vision Deficiency has two affected X chromosomes, and so has both a father with a deficiency and a mother who is a carrier (or also has a deficiency). Many girls carry one affected X and have normal color vision. If a woman with Color Vision Deficiency has children, all of her boys will have the condition.
The altered gene on the X chromosome affects the cones in the back of the retina. The millions of cones detect light and color and enable our vision.
People with normal color vision have trichromatic vision, with three types of cones sensitive to different wavelengths of light. People with mild Color Vision Deficiencies have three types of cones with the sensitivity of one cone set shifted from the normal. Those with more significant Color Vision Deficiencies lack one cone set. People with dichromatic (two-cone) vision see far fewer hues than people with trichromatic (three-cone) vision.
Types
Most people with Color Vision Deficiency (95%) have a red-green type. Only 5% of people with Color Vision Deficiency have a blue-yellow type. Both the red-green and the blue-yellow types have subtypes, depending upon how the cones are affected.
Most people identified as colorblind are actually only partially colorblind. Total colorblindness, called Achromatopsia, is an extremely rare disorder with additional vision impairments.
Treatment and Coping Strategies
Color Vision Deficiency is not curable or treatable. No glasses, contact lenses, medication, or instruction will alter how affected individuals see colors. The best treatment is awareness.
Since children cannot change how they see, the adults around them should make adjustments. The following strategies may be useful for parents.
Explain to the child and his or her siblings that he or she sees colors differently than most people.
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In most cases, accept the color names the child chooses. Only he knows what he sees.
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When you ask the child to retrieve something, use attributes other than color; have her get the shirt with wide stripes or the fuzzy pillow.
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If it is helpful to the child and siblings, adopt a color-relative vocabulary in your household. “It’s blue to me, but it might be purple to him.”
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Be sensitive about wardrobe color choices. Your child’s idea of matching is different than yours.
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Discuss the condition with the child’s teachers and coaches.
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When the child considers future occupations, explain that some professions have color vision requirements. Assist the child with research into potential occupations when he or she is in middle and high school.
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Parents should realize that most people with Color Vision Deficiency do not view it as a handicap or limitation, but rather as an individual characteristic.
School and Color Vision Deficiency
Inform your child’s teachers about the Color Vision Deficiency. Your child may color a different way and may have difficulty with certain tasks. Putting toys away by color, distinguishing colors on maps, or reading certain colors of lettering could be problematic. The child cannot change how he or she perceives color; more time or further instruction will not overcome the problem. Teachers and parents should modify assigned tasks so that the child can succeed.
Teachers should be prepared to deal with any negative peer reaction to the child’s work. A simple explanation to the children that not everyone sees things the same way and an example of acceptance should alleviate any teasing.
Disadvantages and an Advantage
The most obvious limitation for people with Color Vision Deficiency is reduced occupational choice. Operators of public or commercial transportation must have normal color vision, as must police officers, firefighters, and most pilots. Some occupations do not have formal requirements but the nature of the work may put people with Color Vision Deficiency at a disadvantage. Before pursuing a career as a designer, geologist, chemist, printer, or another profession where distinguishing colors is important, young people with Color Vision Deficiency and their parents should research the occupation.
Traffic lights generally look different to people with Color Vision Deficiency. Most drivers with the condition rely on the position of the lights and rarely have problems.
There may be an advantage to having Color Vision Deficiency. Because of their practice at detecting subtle differences in shading, affected individuals may be able to detect camouflage more easily than people with normal color vision. An animal surrounded by vegetation or a camouflage net might be in plain view to their practiced eyes.
