The general symptom of cataract is a gradual loss of vision without discomfort such as eye pain during the whole process. If a patient suddenly feels a significant loss of vision without pain, he or she should consider whether there is a combination of other problems, such as a lesion in the fundus: fundus hemorrhage, optic nerve papillopathy, or retinal detachment, etc. At this time, do not mistake it for a cataract, and you must see an ophthalmologist immediately. In the process of age-related cataract development, there is a period called expansion period. During this period, there is more water accumulation in the lens, which makes its volume swell sharply and the anterior chamber become shallow, patients can feel the speed of vision loss at this time. At this time, patients can also feel redness, eye pain, eye swelling, headache, nausea, vomiting and other systemic symptoms, and their vision decreases sharply, even only light perception, or blindness.