Glaucoma (the sneak thief of sight) refers to a group of eye diseases that affect the optic nerve and may cause vision loss. Optic nerve damage in glaucoma is primarily due to elevated intra-ocular pressure (IOP) within the eye. Glaucoma is classified either as open-angle (the more common chronic condition which is usually painless) or angle-closure glaucoma (the more unusual type which often occurs suddenly [acutely] and is associated with pain and redness of the eye). The elderly, African-Americans, and people with family histories of the disease are at greatest risk. There are no symptoms in the early stages, and by the time the patient notices vision changes, there is visual loss due to glaucoma
