The symptoms of closed-angle glaucoma are often episodic, such as eye swelling and pain, sore nose, sudden increase in eye pressure or even cause headache, nausea, vomiting, loss of vision and iris vision, etc. Once these occur patients should seek prompt medical attention. However, patients often have mild symptoms before an attack, such as mild eye swelling and vision loss, which are relieved by patients resting and sleeping, and they may be careless and not go to the doctor. Primary open-angle glaucoma is known as the “thief of light” because it has a very insidious onset and no obvious symptoms. When you suddenly notice that your eyes are not seeing well and your field of vision has narrowed, it is too late to go to the doctor because you are already in the middle or late stages of glaucoma. Therefore, it is highly recommended that middle-aged and elderly people have an annual eye checkup to measure their eye pressure and check their fundus.