Glaucoma is an eye disease in which the pressure inside the eye is either intermittently or continuously elevated. Elevated intraocular pressure can manifest itself with a variety of symptoms depending on its cause. Persistent high intraocular pressure can cause damage to various parts of the eye and visual function, resulting in decreased visual acuity and reduced visual field. If left untreated, the visual field can be completely lost or even blind. Therefore, glaucoma is one of the major diseases that cause blindness. Early manifestations of glaucoma include: Elevated intraocular pressure The normal intraocular pressure range is 10-21 mm Hg when measured with a Hewitt’s ophthalmometer, and the eye is elastic when touched with a finger. When the pressure rises to 40-70 mmHg, the eye is hard like a stone when pressed with the finger. Narrowing of the visual field and reduced visual acuity Due to high intraocular pressure, the optic nerve is damaged, and vision loss and foggy vision mostly occur at night in the early stage and disappear the next morning. Headache and eye swelling Due to the rapid increase of IOP, the end of the trigeminal nerve is stimulated and reflexively causes pain in the area where the trigeminal nerve is distributed, and patients often feel migraine and eye swelling. Nausea and vomiting Increased intraocular pressure can also reflexively cause excitation of the vagus nerve and vomiting nerve centers, resulting in severe nausea and vomiting. The elevated intraocular pressure causes corneal edema and refractive changes, which can lead to an orange-red outer ring, a violet inner ring, and a green ring in the middle. When the IOP returns to normal, the ring disappears. This phenomenon is medically known as iridopsia. In the case of physiological or cataractous iridopsia, there are no headaches or elevated intraocular pressure. Glaucoma is common in middle-aged and older adults, especially in women, and most of the causes are psychologically related, such as significant mental stimulation, excitement, insomnia, and overexertion. In addition, glaucoma in some patients is associated with genetic factors, so people with a family history of glaucoma should be more alert to the occurrence of the disease. Some patients with glaucoma may show no early signs until they have a small field of vision and difficulty moving, which is often difficult to treat. However, most people will have some of these symptoms in the early stages of the disease, and patients should be aware of them and seek early treatment.