As most parents know and are aware we do vision testing as part of our school health program. Near, distance and color vision are tested in grades SK, 1, 3, 5, 7, 9 and 11. Of course, ANY student can be tested if the parents or the teachers feel they require it. We need to realize that this is simply a SCREENING TEST and cannot replace a full eye examination performed by an ophthalmologist.
So, it may come as a surprise to some that 8% boys and 0,5% girls (1 in 25 kids) have some form of color deficiency (or colorblindness). An affected child sees colors differently and depending on the type of deficiency a child’s view may vary subtly or dramatically.
Possible Signs of Color Vision Deficiency
A child with a color deficiency may:
- Give alternate names to colors
- Draw with an alternate color scheme: green skin or hair, black tree trunk, brown grass
- Describe as similar some shades of reddish and greening
School screening alerts parents and teachers that there may be a color perception issue but DO NOT REPLACE and examination by an eye care professional!! Parents and teachers with normal color vision may be startled by watching a color deficient child take the test: what is obvious to them may be undetectable to the child.
A mild color deficiency is present when one or more of the three cones light sensitive pigments are not quite right and their peak sensitivity is shifted: includes protanomaly and deuteranomaly. A more severe color deficiency is present when one or more of the cones light sensitive pigments is really wrong: includes protanopia and deuteranopia.
Ninety nine percent of the color vision deficient people fall into 1 of the two categories: PROTANS (weak red) or DEUTANS (weak green).
- Protanomaly (one out of 100 males): Protanomaly is referred to as "red-weakness", an apt description of this form of color deficiency. Any redness seen in a color by a normal observer is seen more weakly by the protanomalous viewer, both in terms of its "coloring power" (saturation, or depth of color) and its brightness. Red, orange, yellow, and yellow-green appear somewhat shifted in hue ("hue" is just another word for "color") towards green, and all appear paler than they do to the normal observer. normals call "violet" may look only like another shade of blue.
- Deuteranomaly (five out of 100 males): The deuteranomalous person is considered "green weak". Similar to the protanomalous person, he is poor at discriminating small differences in hues in the red, orange, yellow, green region of the spectrum. shifted towards red for him. From a practical stand point, many protanomalous and deuteranomalous people breeze through life with very little difficulty doing tasks that require normal color vision. Some may not even be aware that their color perception is in any way different from normal nor do their friends.
- Protanopia (1 in 100 males) : these individuals are aware that they have a problem: the brightness of red, orange and yellow is much reduced. This dimming can be so pronounced that reds may be confused with black or dark gray, and red traffic lights may appear to be extinguished.
- Deuteranopia (one out of 100 males): The deuteranope suffers the same hue discrimination problems as the protanope, but without the abnormal dimming. The names red, orange, yellow, and green really mean very little to him aside from being different names that every one else around him seems to be able to agree on.