Glaucoma is usually accompanied by high pressure inside the eye that damages the optic nerve and can result in permanent vision loss. Normal-tension glaucoma (also called low-tension glaucoma) is a unique condition in which optic nerve damage and vision loss have occurred despite of a normal pressure inside the eye.

By definition, people with normal-tension glaucoma have open, normal-appearing angles. In fact, the features of normal-tension glaucoma are similar to primary open-angle glaucoma (POAG), the most common form of glaucoma.

• According to the Baltimore Eye Study, 50% of individuals with changes in their optic disc (the front surface of the optic nerve) and in their visual field had an IOP of less than 21 mm Hg on a single visit, and 33% had an IOP of less than 21 mm Hg on 2 measurements.
• Normal-tension glaucoma is more common in women than in men.
• Normal-tension glaucoma affects adults, with an average age of 60 years.