People with color blindness are born without the ability to properly distinguish colors and assume that others are like them, so they are not aware of the disease. How to determine color blindness and color deficiency? Most of the examinations of color blindness and color deficiency are conducted by primary sensory examination, usually under brighter natural light, and the common methods of identification are as follows. 1, total color blindness belongs to complete cone cell dysfunction, and night blindness (optic rod cell dysfunction) is the opposite, the patient especially likes dark, photophobia, performance as day blindness. The seven-color world is gray in their eyes, just like watching a black and white TV, there is only a difference between light and dark, but no color difference. In addition, there are symptoms such as poor visual acuity, amblyopia, central dark spot, and oscillatory nystagmus. It is the most serious kind of color vision disorder and is less common in patients. 2, red blindness Also known as first color blindness. Patients are mainly unable to distinguish red, and cannot distinguish red from dark green, blue from fuchsia and purple. Often see green as yellow, purple as blue, and mix green and blue as white. There was a middle-aged man who bought a gray wool sweater and wore it, but he was ridiculed because he was a red colorblind person who mistook red for gray. In the early years, there were reports that a red color blind patient became a train driver, because of the wrong signal and caused a train collision. 3, blue-yellow blindness, also known as third color blindness. Patients with blue-yellow confusion, red and green can be identified, less common. 4, total color weakness also known as red, green, blue and yellow weakness. Its color vision impairment than the degree of total color blindness is lower, vision without any abnormalities, and no other complications of total color blindness. When the object is dark and sharp, it can be distinguished; if the color is light and unsaturated, it is difficult to distinguish. Patients are also rare. 5.Partial color weakness There are red weakness (first color weakness), green weakness (second color weakness) and blue-yellow weakness (third color weakness), etc. Among them, red-green weakness is more common. Patients have poor perception of red and green, and when illumination is poor, their color discrimination ability is close to that of red-green blindness; however, when the material color is deep, sharp and the illumination is good, their color discrimination ability is close to normal.