Colour blindness how is it caused

Your eye is a complex and compact structure measuring about 1 inch 2. It receives millions of pieces of information about the outside world, which are quickly processed by your brain. Color blindness — or more accurately, poor or deficient color vision — is an inability to see the difference between certain colors. Though many people commonly use the term "color blind" for this condition, true color blindness — in which everything is seen in shades of black and white — is rare.

Color blindness is usually inherited. Men are more likely to be born with color blindness. Most people with color blindness can't distinguish between certain shades of red and green.

Less commonly, people with color blindness can't distinguish between shades of blue and yellow. You may have a color vision deficiency and not know it. Some people figure out that they or their child has the condition when it causes confusion — such as when there are problems differentiating the colors in a traffic light or interpreting color-coded learning materials.

The most common color deficiency is an inability to see some shades of red and green. Often, a person who is red-green or blue-yellow deficient isn't completely insensitive to both colors. Defects can be mild, moderate or severe. If you suspect you have problems distinguishing certain colors or your color vision changes, see an eye doctor for testing. It's important that children get comprehensive eye exams, including color vision testing, before starting school.

There's no cure for inherited color deficiencies, but if illness or eye disease is the cause, treatment may improve color vision.

Seeing colors across the light spectrum is a complex process that begins with your eyes' ability to respond to different wavelengths of light.

Light, which contains all color wavelengths, enters your eye through the cornea and passes through the lens and transparent, jellylike tissue in your eye vitreous humor to wavelength-sensitive cells cones at the back of your eye in the macular area of the retina. The cones are sensitive to short blue , medium green or long red wavelengths of light. This can be caused by:. Your color vision may also get worse as you get older, especially if you get a cataract — a cloudy area on your eye.

Search the site. Print this Page. Causes of Color Blindness. Learn the basics about color blindness. What causes color blindness? How is color blindness passed down from parents? When a specific type of cone cell is missing or doesn't work properly, a person will have trouble seeing the colour that particular cone cell responds to.

For example, a person with red colour blindness has a defect in red cone cells. Most colour blindness is inherited, although some cases are caused by an injury or disease of the retina or optic nerve , the nerve that takes visual information from the eye to the brain. People inherit colour blindness as a result of a defect on the gene s for colour located on the X chromosome.

Men inherit colour blindness 10 times as often as women do. Colour blindness "shows up" in men because they have only one X chromosome. Since women inherit two X chromosomes, a healthy gene on one X chromosome can override the unhealthy gene on the other. A woman can still have the unhealthy gene; it just doesn't always show up.

She can, however, pass the gene to her children. A person who doesn't have a genetic condition like colour blindness but who can pass it to her children is called a "carrier. Diseases that may lead to colour blindness include glaucoma, macular degeneration, cataracts, uncontrolled diabetes, and multiple sclerosis.

Fading color vision may also occur with age. Colour blindness ranges from very mild to very severe forms, with most people having mild symptoms. People with colour blindness can't see the difference between certain colours.

For example, a person with severe green colour blindness deuteranopia has trouble seeing the difference between oranges, greens, browns, and pale reds. In someone with severe red colour blindness protanopia , all red colours look very dull.

A few people have trouble distinguishing blue. This condition, called tritanopia , is either inherited or is caused by a reaction to drugs or poisons that damage the retina or optic nerve.