Loss of color vision refers to an insensitivity to the ability to discriminate one or some colors. According to the doctrine of the three primary colors, loss of color discrimination of one color is called dichromatic vision, and loss of red color discrimination is called red-blindness. This person has a shortened red end of the spectrum, is less sensitive to the red color of the spectrum, and sees it as a dark color. He drives through red lights, often because the red light is not bright enough for him. What are the tests for loss of color vision? 1, the same color table check method Fake same color table is usually called color blindness checklist, foreign countries have Ishihara Shinobu and Stilling fake same color table, domestic has Yu Zhibing, Jia Yongyuan color blindness check chart. The design principle is that the pictures are composed of dots of the same lightness and darkness (shades of hue) but different colors, and each picture is composed of numbers, letters, patterns or curves with dots of one color, and the bottom of the picture with dots of several other colors. Normal people can make correct judgments because they recognize pictures by color but not by brightness, while people with abnormal color vision recognize them by brightness but not by color, so they cannot make correct judgments. Another kind of picture is composed of dots with the same color but different lightness and darkness, which normal people cannot recognize, but color vision abnormal people can recognize. At present, this method is still used as a screening tool to separate normal people from those with abnormal color vision. 2, FM-100 color test Fornsworth-munsell-100 color tester consists of 93 color discs of different wavelengths (wavelengths of 455 ~ 633 nm), divided into four wooden boxes, each box has a fixed color disc at each end, as a color matching use, the rest of the color discs can be moved. The inspection method is under the fixed illumination, asked to be examined according to the law of color change, sequential arrangement of color discs, each box limited to 2min, the number on the back of the row of boxes recorded on the record sheet, and score for the graph. The graph for normal eyes is a circular graph close to the inner circle; for those who are not normal, the graph is shifted outward in a cogwheel shape in the difficult part of color discrimination. FM-100 color test can be used for color vision abnormalities and quantitative analysis. 3, Farnsworth15 color scale test Check the apparatus for 15 color scale in a box, the inspection method is basically the same as above, requiring 15 color scale arrangement within 2min. Judgment of the results, such as 1 to 15 color coding all correctly arranged or two adjacent color coding before and after the order reversed for through; such as the order of confusion for failure. The results are plotted into a chart to determine whether there are abnormalities in color vision. This test method is relatively simple, high precision, can determine the type and degree of color vision abnormalities. 4, Nagel color vision inspection method color vision mirror is a spectral instrument designed according to the principle of red light and green light properly mixed into yellow light. From the eyepiece in a circular field of view, the lower half of the yellow light, the upper half of the adjustable red light and green light mixture.