If you have some degree of color blindness, you can usually thank your parents. Color blindness is usually hereditary — red/green and blue color blindness is usually passed down from your parents. The gene responsible for the condition is carried on the X chromosome; this is why color blindness affects men far more than women. Color blindness usually means that you have trouble seeing red, green, or blue, or a mix of these colors. It is rare that a person sees no color at all.
Around 8% of the males in the world are color blind. That comes to around 250 million people worldwide. The vast majority of those who are color blind have inherited the condition from their mother, who is not color blind herself but is a carrier. Some people can become color blind due to long-term diseases such as diabetes, multiple sclerosis, liver disease, and almost all eye diseases.
Anatomy of color blindness
If your color blindness is inherited, your condition will stay the same throughout your life. It won’t get better or worse, and there is no treatment for it.
The retina of the eye has two types of light-sensitive cells — rods and cones. Both are located on the retina, the layer on the back of the eye that is responsible for processing the images that enter the eye through the lens. Rods are responsible for seeing in low light conditions and at night. Cones work in daylight and have the job of color discrimination.
You have three types of cone cells, each sensitive to different light wavelengths — one perceives blue, another green, and a third red. When light enters the eye, it stimulates the cone cells and the brain then interprets the signals so that you see the color of the object. Stimulate the red and blue cones simultaneously and you see purple.
While the exact cause of color blindness isn’t known, it is believed there are two causes. Either the cones are faulty, or there is a flaw in the pathway from the cone to the brain. Most people with color blindness can’t distinguish certain shades of red and green.
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