A color vision test, also known as the Ishihara color test, is an assessment of one's ability to differentiate colors. It is used to detect any deficiencies in color vision, such as red-green color blindness. The test consists of a series of circles, or plaques, with dots of different colors and sizes. Some of the dots form one- or two-digit shapes or numbers.
If you have trouble seeing red and green, those shapes will be difficult to see, or you may not see them at all. Anomaloscopes are optical instruments used to diagnose color vision defects. The results of the test are expressed by drawing in pencil the tonality compartments that correspond to the colored caps incorrectly placed between the gray ones. Tetracromy (“supervision”) and protane color blindness are two types of visual impairments that can be detected by a color vision test. Deuteranopia is another type of color blindness that can be diagnosed with this test.
Normal window light is too variable in both illuminance level and spectral composition to be an adequate source for color vision tests. It's possible to get a normal result on the color vision test, but still experience a loss of color intensity in one eye or the other. The anomaloscope contains a red-green scale in which you can read a number that is proportional to the amount of red in the mixing field, and a Y scale, from which you can read a number proportional to the luminance of the test color. The observer must indicate which of the four comparison colors (up, down, left or right) is most similar to the central test color. The Titmus color perception test consists of a slide containing reproductions of pseudo-isochromatic plates from Ishihara. This part of the test makes it possible to determine the position on the gray scale of the colored caps that appear gray to the observer.
Third, even when choosing a set of colors, the individual variation in the lens of the eye and in the coloration of the back of the eye means that a single choice of colors will not be optimal for all observers. Pseudoisochromatic plates for testing color perception from American Optical Corporation, Buffalo, NY (14215). Richards and his colleagues (197) compared two lamps manufactured in the United States, the GE Chroma 70 and the fluorescent Verd-A-Ray Criticolor, with the Macbeth Easel lamp, which was designed for use in tests with screening plates. The test makes it possible to determine the neutral zones (colors that are confused with gray) and tests the discriminative chromatic capacity at each of the four levels of saturation. With its high prevalence (8% of men) and its wide range of professions that restrict hiring people with colorblindness for aesthetic or safety reasons, clinical color vision standards must be designed to be quick and simple to implement. Color vision tests are most commonly used to diagnose deficiencies in color vision (color blindness), although several standards are designed to classify normal color vision into sub-levels. These tests are designed to separate observers with color problems from normal observers, but they do not indicate the wide range of color skills and aptitudes that exists among normal observers.
