Glaucoma is a group of eye diseases that are characterized by pressure that is too high for the optic nerve to withstand. The optic nerve is crucial in sight, as it is the nerve that sends all of the images created by the eye to the brain. Given it's cruciality, damage to the nerve from glaucoma results first the loss of peripheral vision, and then central vision. Glaucoma can be treated in many different fashions with medication and often times surgery is required to stop it from completely damaging the optic nerve. Glaucoma develops at a different rate for every individual, meaning that one individual might experience nerve damage from a relatively low amount of pressure, while another individual might have noticeably higher pressure and yet be able to withstand it for years without developing any damage. There is several different types of glaucoma with the most commong type being: primary open angle glaucoma (POAG). POAG is dubbed the "the sneak thief of sight" because it typically has no symptoms. Another type of glaucoma is acute angle-closure glaucoma, which is commonly characterized by an acute rise in the intraocular pressure. Acute angle-closure glaucoma occurs in eyes that are vulernible as the pupil dilates, thus blocking the flow of fluid through it. Acute angle-closure glaucoma will generally cause pain and blurred vision, and in more extreme cases leads to irreversible visual loss within a short time. In such cases immediate treatment is required. Some symptoms of the disease are: halos around bright lights as well as the loss of sight(slowly or rapidly). If you suspect that you or someone you know is affected with glaucoma it is extremely important to have it checked out by an eye doctor immediately because untreated glaucoma can result in total loss of sight.