While people with normal vision can differentiate between more than 100 different hues, 1 person in 100 has the severe form of color blindness known as “dichromacy,” which restricts the number of colors seen to two—yellow and blue. To the dichromat, red, yellow, orange, and green all appear as yellow, while blue and violet appear to be blue. All other colors appear to be white. Color perception comes from cone cells at the center of the retina, which have three classes of light-activated pigments. Color deficiency arises from a lack or an abnormality of these pigments. As color coding takes on increased importance in everyday living, it is important that color-blind individuals learn to cope with their visual defect. Because a problem with color vision can have a big impact on a person's life, it is important to detect the problem as early as possible. Some acquired color vision problems can be treated, depending on the cause. For example, if a cataract is causing a problem with color vision, surgery to remove the cataract may restore normal color vision. In children, color vision problems can affect learning abilities and reading development. Although color blindness cannot be cured, there are ways to compensate for the visual deficiency.