This document describes how to interpret the “Ishihara’s tests for colour deficiency. Concise Edition” published in 2000.
“Ishihara’s tests for colour deficiency” comes with instructions, but these always seem to get lost. Therefore, this knol describes the key concepts you need to know in order to perform and interpret the tests. Unless stated otherwise, the information comes from the instructions accompanying the “Ishihara’s tests for colour deficiency. Concise edition.” published in 2000, by Kanehara & Co., Ltd, Tokyo, Japan. The instruction manual was written by Shinobu Ishihara, MD, Professor Emeritus of the University of Tokyo.
The plates test for color deficiency of congenital origin, which are generally red-green deficiencies. According to Dr. Ishihara, in red-green deficiencies, blue and yellow appear to be “remarkably clear compared with red and green colours.”
The book contains 14 plates. The responses for each plate 1-11 are as follows:
|Plate Number||Normal Response||Red-green color deficiency||Comment.|
|9||”nr”||2||Only count as abnormal response for tallying totals if read “2” on plate 9 more easily than read “2” on plate 8.|
|11||can trace line||“nr”|
|Total # of plates 1-11 read correctly:||10 or 11||1 to 7||8 or 9 correct is a “rare” finding, per Dr. Ishihara, and would require anomaloscope or other testing.|
“nr” means the plate cannot be read.
Red-green color deficiency can be subdivided into several types.
|Normal||Protan (strong)||Protan (mild)||Deutan (Strong)||Deutan (Mild)|
|Patient experience:||Blue-green appears as grey.||Green appears as grey, as does purple-red, its complement.|
|12||35||5||(3) 5||3||3 (5)|
|13||96||6||(9) 6||9||9 (6)|
|14||can trace 2 lines||sees purple line||sees purple (+/- red) line||sees red line||sees red (+/-) purple lines|
A person with total color blindness can still read plate 1 as the number 12, but should not be able to read plates 2 through 11 or plate 14. The directions do not explicitly say if the person with total color blindness would see plates 12 or 13, but one would have to assume they would not.
==Test in a room “lit adequately by daylight,” as opposed to direct sunlight or electric lights.
==Hold plates 75 cm from the subject and tilted so that the plane of the paper is perpendicular to the visual axis.
==Patients must answer with no more than a 3 second delay.
==Keep the book closed except during use because sunlight will fade the plates.