In the early stage of cataract, the vision is slightly dim and often cannot be detected by oneself. The vision of both eyes (distance vision and near vision) gradually decreases at the same time, and only when the vision decreases to a certain degree does one pay attention to it. If there is mild visual impairment, or the eyes are easily fatigued, or there is a black spot in front of the eyes and it is fixed, or there is a cloud in front of the eyes and the vision is unclear, or there is double vision (diplopia), etc., we should pay attention to it. The early symptoms of cataract are as follows: 1. Appearance of rainbow: when looking at lights, the phenomenon of colored halos appears. 2. Blurred vision: Cataract patients gradually blur their vision and sometimes feel the appearance of an aperture around the light as well as the color of the object is not bright enough. This development process is related to the degree of cloudiness of the crystal. Generally, cataract patients will have different degrees of blurred vision. However, the progression of symptoms is generally quite slow and depends on the location of the most cloudy lens and its progression. 3. Appearance of double vision: When looking at something, sometimes double vision or overlap can occur. A dotted or lamellar shadow with a fixed position and constant shape may appear in front of the eyes. 4.Reduced degree of presbyopia: Older people who originally have presbyopia may suddenly find that the degree of presbyopia decreases. In fact, this is not a good sign, which is one of the early symptoms of cataract because of the increase of lens convexity and the change of refractive proximal point when the cataract first occurs. 5.Dark shadows appear in front of the eyes: When there are fixed, unchanging dark shadows in front of the eyes, you need to pay attention to whether they are cataracts. We should pay attention to distinguish it from mosquito flying.