The story of a color blind child

Color blind

Photo courtesy of Templatemonster.com

It’s that time of year again. Every fall, our local doctors of optometry, along with school nurses and a plethora of volunteers, corral students through our Lions Club’s Sight Savers trailer performing vision screening. And, every fall I have concerned parents rushing in their children to confirm if there is an eye problem. This year was no different.

Last week I entered my exam room to see a first grader who, it was determined, was color blind. Of course, his father did not believe the testing was correct and proceeded to confirm that his son new ALL of his colors and that there was NO WAY he could be color blind. I pulled out my trusty color vision test; administered the test to the son; and showed that indeed he was color deficient. On one page of the test with the number “35”, a color deficient person would only be able to see one digit. The boy proudly and confidently proclaimed that the number on the page was “5”. Even with prodding and cajoling from the father, his son could only see the number “5”.

A little physiology lesson:

In the retina, there are two types of nerves – cones that see color, and rods that see light. The cones are further differentiated in to three types – one that is stimulated by red light, one by green light and one by blue light. In order to have “normal” color vision, all three cones need to be present. If one of the cones is missing, or more commonly not as sensitive, then the person would have confusion of certain colors. This student has a deficient green cone. I explained this condition to the father and the student and how it would affect him.

For instance:

If we have green paint and mix it with red paint, we make brown paint. (Green + Red = Brown)

If you cannot see the green, then red and brown look the same. (Green + Red = Brown)

If we mix green with blue, we make aqua. So, blue and aqua look the same. (Green + Blue = Aqua)

This confusion of colors is what is known as “color blindness” or more correctly “color deficiency”. I explained that it is important to let the teachers know so they do not grade down for improper answers, and discussed job restriction for color deficient people. The two most common job restrictions are law enforcement and commercial aviation. If a color deficient police officer was told a suspect has a brown coat on and stops someone with a red coat on, that just doesn’t work. I do have several patients who are pilots and are color deficient. They are able to get licensed to fly, but not to fly at night due to the need to differentiate the colored lights on airstrips – no commercial or airliner work.

Facts about color deficiencies:

  • The gene for color deficiency is carried on the X chromosome
  • Somewhere between 8 to 10 percent of the male population in the US is color deficient
  • Less than one half percent of the female population in the US is color deficient
  • Men cannot pass color deficiencies on to their sons; it passes through mothers who are carriers for the gene
  • The incidence of color deficiency is highest in Caucasians; then Asians, then Hispanics, and lowest in African Americans
  • Red-Green defects account for over 95 percent of color deficiencies
  • Blue-yellow color blindnessis a dominant, not sex linked trait, which means both men and women are equally affected.
  • John Dalton wrote the first known scientific paper (1794) regarding color blindness. He was color blind himself.
  • Color deficient people hate to be asked “What color is this?”

~ Steven Sage Hider, OD
California Optometric Association
http://www.coavision.org
http://www.eyehelp.org

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Color blindness – the causes and the effects

When we think of someone being color blind, we may think that he sees the world in black and white, or shades of gray.  But that is extremely rare.  In fact, almost 8% of men have some form of color vision deficiency where certain colors are more difficult to distinguish, or do not appear as vivid as other colors.  (Perhaps that explains the questionable wardrobe choices my husband sometimes makes.)

What causes it?

Most cases of color vision deficiency are inherited and passed down from the mom.  The photoreceptors in the retina responsible for color are called cones.  Each cone is sensitive to a certain color, in particular, red, green or blue.  If a person has inherited a recessive gene that causes one or more of the cones to be absent or to not function properly, then he will have abnormal color perception.

Photo courtesy of entirelysubjective on Flickr

Photo courtesy of entirelysubjective on Flickr

Some cases of color vision deficiency are acquired later in life as a result of a disease.  More common causative diseases are glaucoma, macular degeneration, and diabetes.  If you notice a change in your color vision, make sure to be evaluated by your optometrist. For eyecare providers, we tend to distinguish color vision deficiency into two broad categories.  Red-green and blue-yellow.  Red-green is inherited and the most common deficiency.  Those with this defect can still see red and green, but the colors are more difficult to distinguish and they may not appear as vivid as to the normal eye.  For example, red and green signal lights may look the same.  One may appear brighter but the lights may both look white.  (For this reason, I’m not a fan of the horizontal traffic lights in some smaller towns.)  Most people who have color vision deficiency have a mild form and are not disabled by this condition.

The other form of color deficiency is blue-yellow where patients have a difficult time distinguishing blue from green or yellow from violet.  This is less common and is usually caused by certain eye diseases.  Unfortunately, for many of these patients, color deficiency is just one visual problem among others.  These patients may also suffer from dimming of vision or distortion of vision.  Often times, bright lighting is helpful for these patients, and occasionally tinted lenses. 

How can I help someone that’s color deficient?

Of course, a comprehensive eye examination is important to rule out any causes of color vision deficiency other than genetics.  This also helps to determine the severity.  Most color deficient individuals carry on like normal without it interfering with their daily lives.  A helpful tip would be to not use the colors red and green as markers because the two colors may appear very similar.  Blue and red will be easier to distinguish.  Unfortunately, those with color vision deficiency should avoid careers that require distinguishing color differences such as airplane pilots, paint mixer, interior designer, etc.

Recently, new developments in tinted lenses have been able to allow some color vision deficient patients be able to see colors they have never seen before.  Sounds promising!

~Cindy P. Wang, OD, FAAO
California Optometric Association
http://www.coavision.org