Open-angle glaucoma generally affects both eyes, although intraocular pressure (IOP) levels and the extent of damage to the optic nerve often differ. The first nerve fibers damaged are those necessary for peripheral vision. People with advanced open-angle glaucoma can have 20/20 vision when looking straight ahead but may have blind spots (scotomas) for images located outside the center of the visual field. Eventually, the fibers needed for central vision may be lost as well.
Unlike the open-angle form, closed-angle glaucoma sometimes occurs as acute attacks, as IOP rises rapidly to a dangerous level. Signs of an attack include severe pain in the eye, nausea and vomiting, blurred vision, and rainbow-colored halos around lights.