- Vision & Eye Care
What is Color Blindness?
By Joan Whetzel
For those of us who see the world in color, in all its glorious rainbow tints and shades, it would be hard to imagine what color blindness looks like or feels like. Yet the 5 to 8 percent of all men (1 in 12 men) and approximately 0.5 percent of all women (2 out of every 100 women) who experience this condition, wonder just the opposite, "What would it be like to see the world in its true, living color?" Here are the basics of color blindness, how it works, and how people can learn to live and work with the visual restrictions of color blindness.
How the Eyes Work - the Basics
The retina, at the back of the human eye, contains rods and cones, which produce sight when stimulated by light. The rods provide night vision but can't make out color and the rods perceive color and work well in daylight conditions but not after dark.
What Is Color Blindness?
Color blindness prevents the person from seeing either a single color - red, green or blue - or a combination of these colors. In rare instances, a person may see no color except black, white and shades of gray (monochromasy). Color blindness makes learning more difficult and may prevent the person from getting certain jobs that are dependent on the person being able to distinguish colors.
Types of Color Blindness
Color blindness comes in many types and degrees of color vision deficiency. The average person who sees all colors of light (red, blue and green) and their various mixed shades normally has trichromasy. A person with mild deficiencies of color vision in one of the three colors still sees the color, but they don't quite see it like a person with normal vision. They may see the red, blue, or green with less saturation of color or as a different shade. In this case, the person may not be aware of their color vision deficiency.
Most people with color blindness will lack the ability to distinguish one or two of the colors completely (dichromasy). These people know they have a problem with color perception because the problem has become obvious. They are unable to perceive any distinction between red, orange, yellow, and green. They all run together and look like one big blob.
Causes of Color Blindness
There are several causes for color blindness. Most are genetic, others are due to changes in vision over time. Among them are:
· Genetics - the genetic coding got failed to carry the correct instructions for the perception of color.
· Other Vision Problems - macular degeneration, cataracts, glaucoma, diabetic retinopathy
· Eye Injuries
· Medication Side Effects
Symptoms of Color Blindness
Many times, those with color blindness and their friends and family are unaware of the problem. However, if you suspect that you, a friend, or a loved one may have this conditions, the signs to look for include:
· The ability to see some colors (i.e. blue and yellow) but not see others (red and green).
· The ability to see colors that appear to be a different hue or shade than what others around you are seeing.
· The ability to see only a limited number of color shades, compared to the thousands of colors that others see.
· Only seeing black, white, and shades of gray.
· The inability to see the brightness of colors as other people perceive color brightness.
Diagnosing Color Blindness
Color blindness can dramatically affect a person's life. That's why it's important to be tested early. During a physical, your physician may check for color blindness. Frequently, when being hired for certain jobs, a pre-employment physical will be required, which usually includes a test for color blindness. Some eye doctors will test for color blindness on the initial visit. However, one can be requested by the patient at any time they suspect a problem.
The color blindness test is usually operated through a lighted instrument that looks something like a microscope with eyepieces that come up around the eyes to shield them from external light. This is so that the only light the patient sees comes up through the eyepieces. The patient is shown a rand series of test patterns that, to people with normal vision, look like a circle full of multi-sized dots of different colors and shades of colors. In the center of each circle, a number will appear in dots of a contrasting color. The test patterns will appear in varying shades of blue, yellow, green, and red to test for the type of color blindness (red/green, blue/yellow) and the degree of their color deficiency. Do they have a full fledged red/green color blindness or merely a red-, blue-, green-, or yellow-weakness that allows them to see only a limited number of hues or shades?
Treating Color Blindness
There is no treatment or cure for genetic color blindness. Some the color vision problems that are acquired later can be remedied, depending on the source of the problem. The following treatments sometimes help people with color vision problems to improve their color perception:
· Applying colored contact lenses to help distinguish between colors. The lenses have one drawback in that they sometimes distort visual acuity.
· Surgery to remove cataracts can improve color vision for cataract patients.
· Glare blocking glasses lessen brightness or glare, making it easier to perceive differences in color.
· Learning to look for other visual clues to determine the color of certain objects. For instance, when outdoors, knowing that trees and grass are always green, then comparing them to other objects, the person with color blindness can figure out if the other objects are green also. The person with color weakness can tell if the other objects are the same shade range as grass and trees or if the object is closer to the blue green of the Caribbean Sea or closer to the yellow-green of a Day-glo® highlighter pen.
Learning to Live and Work with Color Blindness
People with color blindness won't be able to work certain jobs. Electricians, for example, must know the difference between colors because electrical wiring ins color-coded for safety reasons. Painters will not be a good job choice since paint is all about color, and getting the wrong color on the walls will cost you business. Fashion design may also be a poor choice for the same reason, fabric choices depend on colors and shades matching. Cooks need to be able to determine the color of meat to know it's doneness.
Color blindness in drivers is the reason that the colors on the traffic light signals are positioned the way they are. Vertical traffic signals have the red light on top, yellow in the middle, solid green either at the bottom or second from the bottom, and the green arrow (if the intersection calls for one) is placed in the bottom-most position. For horizontal traffic signals, it varies with the driving rules of the country. But basically, in countries requiring cars driven in the left lane (i.e. Great Britain) the red light is mounted on the red light is on the right had side of the signal, with the solid green light on the left, the green arrow on the far left, and the yellow between the solid green and red. Countries where cars drive on the right-hand side of the road, the red light is on the left-hand side of the signal, the solid green on the right side and the green arrow, and the yellow separating them. People with red, green, or combination red/green color blindness need only learn the position of the light to know whether they should go, slow down, or stop.
There was a story once about when the original Disney Land was built. Prior to clearing the land, the smaller trees that were to be cleared away were tied with green ribbons (meaning go ahead and dig them up) and the larger trees - the trees Mr. Disney wanted to keep - were tied with red ribbons (meaning "stop" and don't tear these trees down). Unfortunately, the bulldozer driver was color blind, so he tore out all the big trees and left all the little, scrawny ones. So you can see how a simple thing like testing the drivers for color blindness, and/or choosing blue and yellow ribbons might have had a different outcome.
For parents want to help their children succeed in life, consider the following suggestions:
· During routine eye exams, have your children tested for color vision problems.
· Let your child's teachers and school personnel know that your child has color vision problems as well as the type and severity of their color blindness or weakness. And set up a program that will help them succeed in school.
· Teach the child with color vision problems ways to determine the colors of objects when the objects fall in the range of their color deficiency.
· Pair the child with another child who has normal color vision.
By discovering ways to work around color vision deficiencies, the person with color blindness or color weakness can succeed in regular life situations. They can even drive without fear of mistaking a red light for a green light.
Testing Color Vision. What Is Color Blindness and the Different Types?
Web MD. Eye Health Center - Color Blindness.
The US National Library of Medicine. Color Blindness.