Glaucoma, normal tension: Glaucoma in which the intraocular pressure is normal but there is progressive optic nerve damage and visual field loss. Risk factors include a family history of normal tension glaucoma, Japanese ancestry, and a history of heart disease. This disorder is believed due to poor blood flow to the optic nerve or other impairment of the optic nerve. Treatment is to keep eye pressures as low as possible with eye drops, laser or other eye surgery. Also known as low tension glaucoma or normal pressure glaucoma.