Any of various abnormal conditions characterized by inability to distinguish colors. The most common form is daltonism, occurring mostly in males (approx. 8% of Caucasian males) as a sex-linked inherited trait characterized by an inability to distinguish red from green. Total color blindness, or achromatic vision, is rare and due to a defect of the retina.
The inability to perceive colors normally. The level of defect varies from mild to severe. Affected people cannot distinguish between certain shades of color, most commonly red and green. Only rarely do people who are color blind see the world only in various shades of gray.
Any of various conditions in which certain colors are confused with one another. True lack of color appreciation is extremely rare, but some defect of color discrimination is present in about 8% of Caucasian males, and 0.4% of Caucasian females. The most common type of color blindness is daltonism (protanopia), or red-blindness, in which the person cannot distinguish between reds and greens. Occasional cases are due to acquired disease of the retina but in the vast majority it is inherited. The defect is thought to be in the functioning of the light-sensitive cells in the retina responsible for color perception.
A genetic or acquired abnormality of color perception. Complete color blindness, a rare disease, is called achromatopsia. Red-green color blindness, which affects about 8% of the male population, is an X-linked trait. Although the term “color blindness” is used frequently, it is inaccurate. “Color deficiency” is a more accurate description.
The inability to differentiate between different colors is especially critical when someone can’t tell red from green, a significant issue in the context of traffic lights. This particular form of color vision impairment is termed “color defective unsafe.” There are also less severe forms of color recognition issues that generally don’t have a major practical impact.