Normal-Tension Glaucoma

Normal-Tension Glaucoma

Normal-Tension Glaucoma Overview

Glaucoma is usually 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 a normal pressure inside the eye.
Eye pressure, called intraocular pressure (IOP),is measured in millimeters of mercury (mm Hg). Normal eye pressure ranges from 10-21 mm Hg. Most people with glaucoma have IOP of greater than 21 mm Hg; however, in normal-tension glaucoma, people have IOP within the normal range.
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 (see Primary Open-Angle Glaucoma).

• Although the occurrence of normal-tension glaucoma varies worldwide, it is very prevalent in Japan.
  
  
• In the United States, up to 15-25% of people withopen-angle glaucomaexperience normal-tension 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.