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Colour Blindness Test
     These series of tests are designed to provide a quick and accurate assessment of colour vision deficiency.

How to use this test

     The original card version of this test (by Dr. Shinobu Ishihara) was 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 colors. This electronic version may also produce some discrepancies as the image has been opitimized for web-based delivery and with a monitor resolution of 800x600 and 256 color display or greater.The results of this test are not to be considered a valid medical test for colour blindness because of the discrepancies noted. If you have any queries about your own possible colour vision deficiencies consult your doctor.
     Position yourself about 75cm from your monitor so that the colour test image you are looking at is at eye level,read the description of the image and see what you can see.

Images obtained from:
Test for Colour Blindness by
Dr. Shinobu Ishihara
Professor Emeritus of the University of Tokyo
Kanehara Shuppan Co.,Ltd
Tokyo,Kyoto(1962)

COLOUR BLINDNESS TEST

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Backgound (Important as you go along with the test)

     Most cases of colour vision deficiencies are characterized by red-green deficiency which can be classed in two tyoes;

     1. A protan type which may be absolute (protanopia) or partial (protanomalia).
     2. A deutan type which may be absolute (deuteranopia) or partial (deuteranomalia).

     In protanopia the visible range of spectrum is shorter at the red end compared with that of normal, and that part of the spectrum that appears blue-green in the normal appears to those with protanopia as gray.
     In deuteranopia the part of the spectrum that appears to the normal as green appears as gray.Purple (the complimentary colour of green) also appears as gray.
     In protanomalia and deuteranomalia,no part of the spectrum appears as gray,however the part of the spectrum that appears to those with protanopia as gray will appear as grayish indistinct colour to those with protanomalia and similarly, the part of the spectrum which appears gray to those with deuteranopia will appear as an indistinct grayish colour to those with deuteranomalia.
     As a result of this red-green colour deficiencies show blue and yellow colours clearer than red and green colours.
     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 colour blindness, the sensitivity to the 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 function.

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