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This book contains sixteen pseudo-isochromatic plates for testing color vision, together with a small pamphlet of directions for their use.
The series consists of the following: (1) Two simulator plates. A person who, provided his vision with or without glasses is 0.3 or better, says that he cannot read these plates is a simulator (of color blindness). (2) Ten plates, all of which should be decipherable by persons with normal color vision. (3) Four dissimulator plates. These plates, which resemble superficially the preceding ten plates, have no figures. A person who points out certain figures on these plates is a dissimulator.
The plates are to be used preferably in full daylight, and each should be read within fifteen seconds. Plates III, IV, VII and VIII are for detecting deuteranopia, and plates V and VI are for detecting protanopia. Plates IX to XII, which are extremely difficult, are
Duggan WF. Tabulae Pseudo-Isochromaticae.. Arch Ophthalmol. 1936;15(4):792–793. doi:10.1001/archopht.1936.00840160216025