Glaucoma is a condition where the intraocular pressure exceeds the tolerance limits of the tissues within the eyeball, especially the optic nerve, causing characteristic optic nerve atrophy and visual field defects. In the early stages of glaucoma, the following symptoms may occur: First, there is eye pain, which may also be accompanied by headaches; Second, transient phenomena of rainbow vision or foggy vision, resembling the appearance of rainbow-like halos around light sources such as light bulbs; Third, there is a family history of glaucoma, especially if suspicious symptoms are present; Fourth, the eyeball becomes harder, and may feel as hard as a stone. Fifth, unexplained decrease in vision or visual field defects. Some glaucomas have atypical early symptoms, but the presence of the above symptoms should be taken seriously and prompt a hospital visit for diagnosis. High-risk groups for glaucoma should undergo annual eye exams to prevent the disease.