Color blindness is the inability to perceive colors in a normal fashion. The most common forms of color blindness are inherited as sex-linked (X-linked) recessive traits. Females are carriers and males are affected. As a result, approximately 1 in 8 males is color blind as compared to less than 1 in 100 females. The most common form of color blindness is red-green. There is a wide range of variability within this group from very mild to extreme. The second most common form is blue-yellow. A red-green deficit is almost always associated with this form. The most severe form of color blindness is achromatopsia, the inability to see any color. It is often associated with other eye problems such as amblyopia (lazy eye), nystagmus, photosensitivity, and extremely poor vision. The symptoms of red-green and blue-yellow color blindness may be so mild that affected people are unaware they are color blind unless specifically tested. Parents may notice color blindness in a more severely affected child at the time the child would normally learn colors. Several color vision tests are available through a primary physician or an eye specialist (ophthalmologist). Testing for color blindness is commonly performed along with other vision screenings. There is no known treatment. People with this condition need to learn to cope. Color blindness is a life-long condition. Color blindness may exclude people from some jobs, such as being a pilot, where color vision is essential. People with red-green color blindness may also fail to notice the presence of blood in the urine and stool. In red-green color blindness, red and green are perceived as identical. This is the most common type of colorblindness. It is also known as deuteranomaly, deuteranopia, and Daltonism. The term “Daltonism” is derived from the name of the famous chemist and physicist, John Dalton (1766-1844) who had this disorder.