Color blindness (also known as color vision deficiency, or CVD) is the inability or decreased ability to see color. There are different types and causes of color blindness. Most color blindness is inherited, caused by an abnormality in the eye. Photopigments are the molecules in the eye that detect color. Defects in certain genes affect the ability to make photopigments, leading to color blindness. Based on the particular photopigment defect and how the eye responds to light, there the three different kinds of colorblindness. The most common is red-green color blindness, followed by blue-yellow color blindness. Only very rarely does someone have total color blindness, which is the inability to see any color. Sometimes color blindness is caused by damage to the eye, the optic nerve, or even parts of the brain that process color information. Cataracts, which cloud the eye’s lens, can also lead to a decline in color vision.
According to the National Eye Institute, color blindness affects approximately 1 in 12 men (8%) and 1 in 200 women (.5%) in the world. It is so much more common in men because of how genes are inherited. Colorblindness is passed on through the X chromosome. Males carry only one X chromosome, while females have two. So if a man has a faulty gene on his X chromosome, he will be color blind. But a female needs only one functioning gene on only one of her two X chromosomes to not have color blindness.
Inherited color blindness can be present at birth, show up during childhood, or not appear until later in life. Some people don’t even know they have it until they are tested by a doctor. For others, it can have an affect on their daily life. Color blindness can make it difficult to read color-coded information, which can be a challenge in classroom or work settings. It is especially problematic for children who have not yet been diagnosed. For example, a colorblind child may struggle to read the yellow chalk on a green chalkboard, or be unable to distinguish between paint choices. For adults, decoding traffic lights, reading maps or even choosing matching outfits can be challenging. Most color blind people, however, learn to adapt to their color vision deficiency.