Some of the color weaknesses are red weakness (first color weakness), green weakness (second color weakness) and blue-yellow weakness (third color weakness), among which red-green weakness is more common. Patients with poor perception of red and green and poor illumination, their color discrimination ability is close to that of red-green blindness; however, when the substance is dark and vivid and the illumination is good, their color discrimination ability is close to normal. When the illumination is poor, the color discrimination ability is close to that of red-green color blindness, but when the material is dark and vivid and the illumination is good, the color discrimination ability is close to normal. Green weakness is unable to distinguish or can not distinguish green, mixed light green, the general situation does not affect most of the work and study, but can see yellow and blue, and also feel yellow-blue particularly bright. The clinical causes of green weakness 1, congenital green weakness Green weakness belongs to the X-linked recessive inheritance, manifested by the patient can not correctly identify the red and green, determine the disease of red-green weakness gene is recessive, located in the X chromosome. The male patient has the gene Xby, while the female patient has the genotype Xbxb and the female genotype X(superscript) BXb. Therefore, if the male patient marries a normal female, all sons will be normal, while all daughters will be carriers. If a female chromophobe marries a normal male, all sons will be patients and all daughters will be carriers. If a female chromophobic carrier marries a normal male, 1/2 of the offspring will have sons who are likely to develop the disease, and 1/2 of the daughters will not develop the disease but will be carriers. If a female chromophobe carrier marries a male chromophobe, 1/2 of the offspring will have a son who may develop the disease, 1/2 of the daughters may develop the disease, and 1/2 will be carriers. 2. Acquired green weakness Various pathologies of the eye, such as refractive interstitial, retinal cells, optic nerve and optic center suffering from diseases, can cause green weakness.