There are four common types of glaucoma: 1. closed-angle glaucoma, which is also divided into acute and chronic types. The acute type often has sudden eye swelling and pain, headache, even nausea and vomiting, blurred vision, and red and green circles around the light bulb when looking at it, mostly occurring when straining or staying too long in dark places. If you have the above symptoms, you should suspect glaucoma and need to go to the hospital for examination in time. The performance of chronic type is similar to the open angle glaucoma described below. 2. In open-angle glaucoma, there are no symptoms in the early stage of the disease. For people who lack knowledge of glaucoma prevention and treatment, they usually cannot judge themselves and need to rely on specialized consultation and examination by an ophthalmologist to confirm the diagnosis. This type of glaucoma develops insidiously, and by the time vision loss occurs, the disease is often advanced and the visual field is tubular or lost. Some patients don’t know that they can’t see in one eye until they have poor vision in the other eye. The time for early treatment is lost. 3. Congenital glaucoma. It usually appears in infants or children, and can develop in both eyes or one eye. The main manifestations are larger black eyes than children of the same age, fear of light, tearing, and white eyes. If parents see their children with the above symptoms, they should suspect glaucoma and take their children to the hospital for examination in time. 4.Secondary glaucoma. It is usually caused by other eye diseases and can be preceded by other eye diseases. Commonly caused by traumatic, inflammatory, cataract and fundus disease. Therefore these patients can have their IOP measured regularly so that they can find out earlier if they have glaucoma.