A New Method For Testing Color-Defective Vision

摘要

Since 1999,I have been teaching a course in Color Management and Quality Control as part of the baccalaureate curriculum in Graphic Communication at Cal Poly, San Luis Obispo. In the years that I have taught the course, I have had nearly 1,000 students, and I have required every one of them to take the Ishihara color-blindness test as well as the Farnsworth-Munsell color discrimination test (See my paper, An Analysis of Color Discrimination of University Students in the Graphic Arts from the TAGA 2009 Proceedings on the Farnsworth-Munsell test results). Shinobu Ishihara (1879-1963) was a Japanese ophthalmologist who developed the most commonly used test for color-blindness. His test is used worldwide, and is the basis of both medical and workplace vision testing for people in all walks of life. The Ishihara test is administered to both children and adults, and is valuable in determining if a subject has one of the two most common color defects, which are called protanopia and deuteranopia. Both are forms of red-green color-blindness, and they affect a small percentage of the general population. Ishihara's test, however, does not test for a rarer form of color-defective vision, that called tritanopia. Tritanopia is a blue-green color- blindness which affects a tiny percentage of the population (less than 0.01 percent). Dr. Ishihara clearly never encountered a person with tritanopic vision, though he does acknowledge the possibility of its existence in the booklet that accompanies his test plates. The Ishihara test uses Arabic numerals as the symbols in its charts, a number system that is not used by over 1.5 billion people in the world (The Chinese, who do not use the Arabic number system, represent approximately 25 percent of the world's population). The use of Arabic numerals also presumes literacy of the subject, something that cannot be assumed of very young children, people with mental deficiencies, and people who cannot read the numbers due to an inability to read - illiteracy. These factors make the Ishihara test less than ideal in the modern world. My new method for testing for color-defective vision uses color plates similar to those used by Dr. Ishihara, and supplements those colors with several tests that are effective for detecting tritanopia. The tests will also isolate the two common red-green color defects more effectively so that a test administrator can determine if the subject has protanopia or deuteranopia. In the graphic arts industry we rely on color to make our living. In the commercial work environment we rely on employees who can see and judge color effectively. Both the Ishihara test and the more complex Farnszvorth-Munsell test are commonly used in our industry, and are commonly used as factors in testing new employees and employees for color-critical positions. We can do better as an industry by employing more modern color vision testing methods and systems. Dr. Ishihara's test, though very common, is not as effective as it could be in setting a standard for the measurement of color vision in both clinical and industrial settings. I believe that my method is better suited to the modern world and the use of color on computers, printers, and in the creative arts.