Ishihara's Tests 24 For Color Deficiency Chart 24

Ishihara's Tests 24 For Color Deficiency Chart
 

SHINOBU ISHIHARA M.D., Dr.Med. Sc.
Professor Emeritus of the University of Tokyo
Member of the Japan Academy

Introduction
This series of plates is designed to provide a test which gives a quick and accurate assessment of color
vision deficiency of congenital origin. This is the commonest form of color vision disturbances.
Most cases of congenital color vision deficiency are characterized by a red-green deficiency which may
be of two types; first, a protan type which may be complete (protanopia) or partial (protanomalia), and,
secondly, a deutan type which may be complete (deuteranopia) or partial (duteranomalia).
In protanopia the visible range of the spectrum is shorter at the end compared with that of the normal, and
that part of the spectrum which appears to the normal as blue-green, appears to those with protanopia as
grey. The whole visible range of the spectrum in protanopia consists of two areas which are separated
from each other by this grey part. Each area appears to those with protanopia as one system of color with
different brightness and saturation within each area, the color in one area being different from that of the
other. The red with a slight tinge of purple which is the complementary color of blue-green appears also
as grey.
In deuteranopia, that part of the spectrum which appears to the normal as green, appears as grey, and
the visible range of the spectrum is divided by this zone into two areas, each of which appears to be of
one system of color. The visible range of the spectrum is not contracted, in contrast to protanopia. Purplered
which is the complementary color of green appears also as grey.
In protanomalia and deuteranomalia, there is not part of the spectrum which appears grey. But the part of
spectrum which appears to those with protanopia as grey, appears to those with protanomalia as a
grayish indistinct color, and likewise, the grey part of the spectrum seen by the person with deuteranopia
appears to those with deuteranomalia as a indistinct color close to grey.
Consequently, one of the peculiarities of red-green deficiencies is that blue and yellow colors appear to
be remarkably clear compared with red and green colors. The application of this peculiarity to the test for
color vision deficiencies is the distinguishing feature of this series.
In the congenital color vision deficiencies, although very rare, there is total color weakness. The color
sensitivity of the total color weakness to red and green, as well as to yellow and blue is very low and only
the clear colors can be perceived; but, except for the color sensitivity, there is no abnormality in the visual
functions. The plates in this book form an easy method of establishing the diagnosis on such cases and in
distinguishing them from cases of red-green deficiencies.