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 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 this test 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. 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!! It is not necessary in all cases to use the entire set of images. In a large scale examination the test can be simplified to 6 tests; test, one of tests 2 or 3, one of tests 4, 5, 6 or 7, one of tests 8 or 9, one of tests 10, 11, 12 or 13 and one of tests 14 or 15.

Background:

Most cases of colour vision deficiency are characterised by a red-green deficiency which can be classed into two types;

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

• In protanopia the visible range of the spectrum is shorter at the red end compared with that of the normal, and that part of the spectrum that appears blue-green in the normal appears to those with protanopia as grey.
  
• In deuteranopia the part of the spectrum that appears to the normal as green appears as grey. Purple-red (the complimentary colour of green) also appears as grey.

• In protanomalia and deuteranomalia, no part of the spectrum appears as grey, however the part of the spectrum that appears to those with protanopia as grey will appear as a greyish indistinct colour to those with protanomalia and similarily, the part of the spectrum which appears grey to those with deuteranopia will appear as an indistinct greyish colour to those with deuteranomalia.
  As a result of this red-green colour vision 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 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.

CARD 1:

Both normal and those with all colour vision deficiencies should read the number 12.

CARD 2:

Those with normal colour vision should read the number 8. Those with red-green colour vision deficiencies should read the number 3. Total colour blindness should not be able to read any numeral.

CARD 3:

Normal vision should read the number 29.

Red-green deficiencies should read the number 70.

Total colour blindness should not read any numeral

CARD 4:

Normal colour vision should read the number 5.

Red-Green colour deficiencies should read the number 2.

Total colour blindness should not be able toread any numeral.

CARD 5:

Normal colour vision should read the number 3.

Red-Green deficiencies should read the number 5.

Total colour blindness should not be able to read any numeral.

CARD 6:

Normal colour vision should read the number 15.

Red-Green deficiencies should read the number 17.

Total colour blindness should not be able to read any numeral.

CARD 7:

Normal colour vision should read the number 74.

Red-Green colour deficiencies should read the number 21.

Total colour blindness should not be able to read any numeral.

CARD   8:

Normal colour vision should read the number 6.

The majority of those with colour vision deficiencies cannot read this number or will read it incorrectly.

CARD 9:

Normal colour vision should read the number 45.

The majority of those with colour vision deficiencies cannot read this number or will read it incorrectly.

CARD 10:

Normal colour vision should read the number 5.

Those with colour vision deficiencies will not read the number or read it incorrectly.

CARD 11:

Normal colour vision should read the number 7.

Those with colour vision deficiencies will not read this number or read it incorrectly.

CARD 12:

Normal colour vision should read the number 16.

Those with colour vision deficiencies will not read this number or read it incorrectly.

CARD 13:

Normal colour vision will read the number 73.

Those with colour vision deficiencies should nor be able to read this number or will read it incorrectly.

CARD 14:

Normal colour vision and those with total colour blindness should not be able to read any number.

The majority of those with red-green deficiencies should read the number 5.

CARD 15:

Normal colour vision and those with total colour blindness should not be able to read any number.

The majority of those with red-green deficiencies should read the number 45.

CARD 16:

Normal colour vision should read the number 26.

In protanopia and strong protanomalia the number 6 is read and in mild protanomalia both numerals are read but the number 6 is clearer than the number 2.

In deuteranopia and strong deuteranomalia only the number 2 is read and in mild deuteranomalia both the number 2 is clearer than the number 6.

CARD17:

Normal colour vision should read the number 42.

In protanopia and strong protanomalia the number 2 is read and in mild protanomalia both numerals are read but the number 2 is clearer than the number 4.

In deuteranopia and strong deuteranomalia only the number 4 is read and in mild deuteranomalia both the number 4 is clearer than the number 2.

.

CARD 18:

The normal should trace along the purple and red lines between the two X's.

In protanopia and strong protanomalia only the purple line is traced and in mild protanomalia both lines can be traced but the purple line is easier to follow.

In deuteranopia and strong deuteranomalia only the red line is traced and in mild deuteranomalia both lines are traced but the red line is easier to follow.

CARD 19:

The majority of those with red-green colour blindness can trace the winding line between the two X's.

The majority of those with normal and total colour blindness are unable to follow the line.

CARD 20:

Normal will trace the blue-green line between the two X's.

The majority of those with colour vision deficiencies will be unable to follow the line or will follow a line different to the normal one.

Normal will trace the orange line between the two X's.

The majority of those with colour vision deficiencies will be unable to follow the line or will follow a line different to the normal one.

Normal should trace the line connecting the blue-green and the yellow-green.

Those with red-green deficiencies trace the line connecting the blue-green and purple.

Those with total colour blindness cannot trace any line.

Normal should trace the line connecting the purple and the orange between the two X's.

Red-green deficiencies should trace the line connecting the purple and the blue-green.

Total colour blindness and weakness cannot trace any line.

Both normal and those with colour vision deficiencies can trace the winding line between the two X's.