Glaucoma is a group of eye diseases that gradually damage the optic nerve, most commonly caused by increased pressure inside the eye due to fluid buildup. In some cases, glaucoma can also occur in people with normal eye pressure. In the early stages, most patients are unaware that they have the disease. Vision loss typically begins with a gradual narrowing of the visual field, where central vision remains clear but side vision slowly decreases. If left untreated, glaucoma can eventually lead to blindness. However, early detection and proper treatment can help prevent further damage to the optic nerve. Any vision loss that has already occurred before treatment cannot be restored.