Color vision deficiency is the inability to distinguish certain shades of color. The term “color blindness” is often used to describe this visual condition. Very few people are completely color blind, a condition called achromatopsia, which is the ability to only see things as black and white or in shades of gray.

Color vision is possible due to photoreceptors in the retina of the eye known as cones. These cones have light-sensitive pigments that enable us to recognize color. Each cone is sensitive to either red, green or blue light. The cones recognize these lights based on their wavelengths.

Red-green color deficiency is most common but this does not mean that people with this deficiency cannot see these colors at all. They simply have a harder time differentiating between them, which can depend on the darkness or lightness of the colors.

Blue-yellow color deficiency is less rarer and more severe form of color vision loss than red-green, since people with blue-yellow deficiency frequently have red-green blindness too.

Color deficiency is usually an inherited condition caused by a common X-linked recessive gene, which is passed from a mother to her son. Disease or injury that damages the optic nerve or retina can also cause loss of color recognition. Some diseases that can cause color deficits are:

  • diabetes
  • glaucoma
  • macular degeneration
  • Alzheimer’s disease
  • Parkinson’s disease
  • multiple sclerosis
  • chronic alcoholism
  • leukemia
  • sickle cell anemia

Other causes include:


  • Aging
  • Chemical Exposure

Genetics is the main cause of color deficiency. About 8 percent of Caucasian males and only approximately 0.5 percent of women are born with some degree of color deficiency. The severity of inherited color vision deficiency usually remains the same throughout life.