Total Color Blindness Tests
Total color blindness is a condition in which people have mild to severe difficulty identifying colors. Total color blind people may not be able to recognize various shades of colors and, in some cases, cannot recognize colors at all.
Achromatopsia is strictly defined as the inability to see color. Although the term may refer to acquired disorders such as color agnosia and cerebral achromatopsia, it typically refers to congenital color vision disorders (i.e. more frequently rod monochromacy and less frequently cone monochromacy).
In color agnosia and cerebral achromatopsia, a person cannot perceive colors even though the eyes are capable of distinguishing them. Some sources do not consider these to be true color blindness, because the failure is of perception, not of vision. They are forms of visual agnosia.
Those who suffer from typical total colour blindness show a complete failure to discriminate any colour variations, usually associated with impairment of central vision with photophobia and nystagmus.
With atypical total colour blindness, the sensitivity to red and green, as well as to yellow and blue is so low that only very clear colours may be perceived. There are, however, no further abnormalities in the visual functions.
Our total color blindness tests are designed to be carried out in a room adequately lit by daylight. The presence of direct sunlight or artificial light may produce some discrepancy in the results because of some alteration in the appearance of shades of colour. This electronic version may also produce some discrepancies as the images have been optimised for web-based delivery and with a monitor resolution of 800x600 and 256 colour display or greater.
The results of these tests are not to be considered a valid medical test for colour blindness and merely serve to illustrate the tests available. If you have any queries about your own possible colour vision deficiencies consult your local GP or Medical Practitioner.