- Inability to distinguish one or more colours.The human retina contains three types of cone cells that absorb light in different parts of the spectrum. Absence of these types causes colour blindness to red, green, and blue. Colour blindness is a sex-linked recessive trait (see recessiveness) 20 times more common in men than in women.
* * *inability to distinguish one or more of the three colours red, green, and blue. Most people with colour-vision problems have a weak colour-sensing system rather than a frank loss of colour sensation. In the retina (the light-sensitive layer of tissue that lines the back and sides of the eyeball), humans have three types of cones (the visual cells that function in the perception of colour). One type absorbs light best in wavelengths of blue-violet and another in the wavelengths of green. The third type is most sensitive to longer wavelengths—more sensitive to red.Colour-blind persons may be blind to one, two, or all of the colours red, green, and blue. (Blindness to red is called protanopia; to green, deuteranopia; and to blue, tritanopia.) Red-blind persons are ordinarily unable to distinguish between red and green, while blue-blind persons cannot distinguish between blue and yellow. Green-blind persons are unable to see the green part of the spectrum.Hereditary red-green colour blindness, which affects about 20 times as many males as females, is a sex-linked recessive characteristic. A woman must inherit the trait from both parents to be red-green colour-blind. A red-green colour-blind man and a woman of normal colour vision have daughters who have normal colour vision but are carriers of the trait—that is, the daughters may have red-green colour-blind sons and daughters who are carriers. The sons of a red-green colour-blind man and a woman with normal vision who themselves have normal vision are unable to pass the red-green colour-blind trait on to offspring. The son of a normal man and a carrier woman may be red-green colour-blind, and the daughter of such a union may be a carrier. Thus, red-green colour blindness tends to skip generations.Acquired colour blindness is usually of the blue-yellow type and can be due to retinal diseases, glaucoma, or optic nerve diseases. Total colour blindness (achromatopsia) is an extremely rare congenital affliction that is typically associated with poor vision, nystagmus (rapid, uncontrollable eye movements), and light sensitivity.
* * *
Look at other dictionaries:
colour blindness — colour blind ► ADJECTIVE ▪ unable to distinguish certain colours. DERIVATIVES colour blindness noun … English terms dictionary
colour-blindness — noun [uncountable] Thesaurus: ability to see and problems with seeinghyponym race relations and racismhyponym eye and parts of the eyemeronym Main entry: colour blind … Useful english dictionary
colour blindness — The term colour blindness was introduced in or shortly before 1844 by the Scottish physicist and homo universalis David Brewster (1781 1868) as an alternative for the expression * Daltonism. Brewster s proposal for this new name was inspired… … Dictionary of Hallucinations
colour blindness — noun genetic inability to distinguish differences in hue • Syn: ↑color blindness, ↑color vision deficiency, ↑colour vision deficiency • Derivationally related forms: ↑colour blind (for: ↑color blindness), ↑ … Useful english dictionary
colour blindness — any of various conditions in which certain colours are confused with one another. True lack of colour appreciation is extremely rare (see monochromat), but some defect of colour discrimination is present in about 8% of Caucasian males, and 0.4%… … Medical dictionary
colour blindness — any of various conditions in which certain colours are confused with one another. True lack of colour appreciation is extremely rare (see monochromat), but some defect of colour discrimination is present in about 8% of Caucasian males, and 0.4%… … The new mediacal dictionary
colour blindness — spalvinis aklumas statusas T sritis fizika atitikmenys: angl. color blindness; colour blindness; daltonism vok. Anerythropsie, f; Daltonismus, m; Farbenblindheit, f rus. дальтонизм, m; цветовая слепота, f pranc. achromatopsie, f; anérythropsie,… … Fizikos terminų žodynas
colour blindness — /ˈkʌlə blaɪndnəs/ (say kuluh bluyndnuhs) noun defective colour perception, independent of the capacity for distinguishing light and shade, and form. Also, color blindness … Australian English dictionary
colour-blindness — noun The state or quality of being colour blind … Wiktionary
colour-blindness — See: colour blind … English dictionary