Green weakness has a great impact on our life. In our daily life, green weakness patients often cause car accidents because they cannot recognize traffic lights correctly. It threatens our life and property safety. Therefore, we need to understand what are the diseases that cause green weakness, in order to properly carry out treatment and avoid tragic accidents. 1, false homochromatic chart Usually called color blindness book, it is the use of shades of the same degree but the color of different dots to form a number or graph, in the natural light at a distance of 0.5m to read. Check the green weak book should be put right, each figure shall not exceed 5 seconds. Color vision difficulties in recognition, read the wrong or can not be read, can be confirmed in accordance with the color blindness table provisions belong to what color vision abnormalities. 2, the color harness test is a different color, different shades of wool harness mixed together, so that the person being examined to pick out the same color harness with the standard harness. This method is time-consuming, and can only be roughly qualitative not quantitative, not suitable for large area screening inspection. 3, color mixing tester is nagel according to the principle of red + green = yellow, designed a spectral instrument, it can quantitatively record the amount of red and green light matching required to determine the red and green sense of abnormal, this method can be both qualitative and quantitative.