Recently there was a post on the AERNet mailing list asking for advice on a referral made for VI instructional services for a student whose only concern was “color blindness” (more accurately called a color vision deficiency, or CVD. Whereas some vision-related etiologies may have an associated CVD, most individuals with a color vision deficiency do not have additional (uncorrectable) problems with their vision. In Texas, a student who only presents with CVD would not qualify for the services of a TVI, because Texas’ commissioner’s rules state:
…..a student with a visual impairment is one who:
(i) has been determined by a licensed ophthalmologist or optometrist
(ii) to have no vision or to have a serious visual loss after correction; or
(iii) to have a progressive medical condition that will result in no vision or a serious visual loss after correction.
No doubt, at some time in the TVI’s career, they will be asked to evaluate a student who has a color vision deficiency, and it might help to know more about this condition.
CVD is a deficiency in the way a person sees color. It is an inherited condition that affects males more frequently than females. Most people who are considered "color blind" can see colors, but certain colors appear washed out and are easily confused with other colors, depending on the type of color vision deficiency they have. Red-green color deficiency is the most common form of CVD, but some people might have a reduced ability to see blue and yellow hues. A red-green color deficiency does not mean that people cannot see reds or greens. More accurately it means that people have a harder time differentiating between the two colors.
In red deficiencies (protanopia) the cones in the eyes are not sensitive to long wavelengths (the reds). These look more like beige and appear to be somewhat darker than they actually are. The greens tend to look similar to the reds. Individuals with deuteranopia and deuteranomaly (green deficiency) have cones that are insensitive to medium wavelengths (greens). This is the most common form of color deficiency, and individuals do not see reds and greens in the same way that other people with CVD can. This is the more common form of CVD.
Examples of instructional implications for students with CVD include reading maps, charts, and/or graphs, when interpreting pictures in text books, distinguishing colors used on a SMART Board or PowerPoint presentations when colors are used to distinguish information. When programming for the student with CVD, teachers must make sure that colors are not the only method of conveying important information.
Some of the vision etiologies known to cause a color deficiency are cone dystrophy, cone-rod dystrophy, achromatopsia, Leber’s congenital amaurosis, and retinitis pigmentosa. A student with one of these etiologies should be tested for a color deficiency, and accommodations should be made to the educational program if the student has problems with color.
There are many resources available on the web about color deficiency, but here are a few to get you started. Some will give you pictorial examples of what a person with a CVD is actually seeing:
For testing color:
Information for teachers, with suggestions for adaptations for CVD:
“When a Child Has Color Deficiencies” http://visionkits.com/handouts
Color deficiency test.
How color deficient people see the world (slides):
Color vision test.
All About Color Blindness is a children's book that explains CVD: who has it, how they get it, and how to work around it at home and school.
Book available on Amazon.
Chrissy Cowan, TVI