Improved
6112 HealthChanged
3785 LivesSaved
3568 Lives0 lives impacted in the last 24 hrs Learn More
People with normal vision see a full spectrum of colors. People with color blindness are able to see, but are not able to see all colors correctly.
The genetics of color vision
You may have heard that only men can be color blind. While not entirely true, the majority of color blind people are men. Twelve out of every 100 men are colorblind while only one out of every 200 women are color blind. This is because the gene for seeing color is a recessive gene located on the X chromosome. Women have a pair of two X chromosomes, while men have one X paired with a Y. Because women have two X chromosomes, both X’s must have the defective gene in order for her to be color blind. If a woman has one defective gene and one correct gene, the correct gene wins out and the woman has normal vision, but is a carrier for the defect. Men inherit their X chromosome from their mothers. If a man receives a correct gene, he will have normal vision. If he receives a defective gene, he will be color blind because he does not have a second X to balance out the bad gene.
Rods and Cones
The eye perceives color when light rays strike photoreceptors in the retina of the eye. A photoreceptor is a special, light-detecting cell. The photoreceptors on the outer edges of the retina, called rods, are responsible for seeing black and white images and are more effective at seeing in the dark or at night.
In the center of the retina, photoreceptors called cones are responsible for seeing color. There are three types of cones tuned to a specific color wavelength, red, green, or blue. Color blindness is usually caused by defective or missing cones for one of these three wavelengths of light. Most color blind people have a limited ability to distinguish the colors red and green. In even more rare cases, the problem colors are blue and yellow. The label color blind is somewhat deceiving because people who are color blind can usually see some color. Only in very rare cases does the world appear in black and white.
For some people, color blindness is more a matter of degrees than an inability to see a particular color. Colors may appear washed out or very similar to each other. For other people there is no apparent difference between certain colors. If you are not color blind, imagine the difficulties you could have driving if you could not see a difference between red and green on a stop light.
Causes of color blindness
Color blindness is most often a genetically inherited trait that is present from birth. There is no cure for this type of color blindness. Other factors that can cause color blindness include:
• Parkinson’s disease – This neurological disorder can damage nerve cells in the retina.
• Cataracts – When the lens of the eye becomes cloudy, colors can appear washed out. In this case, cataract surgery to replace cloudy lenses can restore lost color vision.
• Medications – Tiagabine, a drug used to treat epilepsy, has been known to reduce color vision.
• Leber’s hereditary optic neuropathy – This inherited condition is most commonly seen in men.
• Kallman’s syndrome – When the pituitary gland fails, other issues tied to the X and Y chromosomes can develop, such as color blindness.
Most people are able to adapt to color blindness. A friend or spouse can help with coping strategies such as labeling clothing for appropriate color-pairing. Parents should be sure to let the teacher know if a child is colorblind. Children who are color blind may need special attention at school to compensate for information they cannot see correctly. Tests and other printed materials may combine colors in a way that cannot be seen or read by color blind children. Other help may include labeling colored objects or making other adjustments in the classroom.
If you believe you or your child may be color blind, talk to your eye care professional for more advice on coping strategies.
Sources:
All About Vision
National Eye Institute
Add a Comment1 Comments
It should be noted that certain progressive eye disorders can result in loss of color vision for men and women alike: con-rod dystropy, Stargardt's (Juvenile macular degeneration and macular degeneration (the leading cause of blindness in seniors), achromotopsia, or day-blindness also results in partial or total color-blindness.
March 6, 2010 - 6:53amAlso, red and green are the two top colors that are lost.
This Comment