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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 with open-angle glaucoma experience 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.



Next: Normal-Tension Glaucoma Causes »

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Normal-Tension Glaucoma

Glaucoma Overview

Glaucoma refers to certain eye diseases that affect the optic nerve and cause vision loss. Most, but not all, of these diseases typically produce elevated pressure inside the eye, called intraocular pressure (IOP). Normal IOP is measured in millimeters of mercury and can range from 10-21 mm Hg. An elevated IOP is the most important risk factor for the development of glaucoma.

Elevated IOP is sometimes called ocular hypertension. If your doctor diagnoses ocular hypertension, it does not mean you have glaucoma, but it does mean you are at a higher risk for developing the condition, and you should see an ophthalmologist (a medical doctor who specializes in eye care and surgery) frequently.

Half of the people with glaucoma are usually unaware of it until a serious loss of vision has occurred.

Many factors are associated with an increased risk of developing glaucoma, some of which are elevated IOP, a family history, ethnic background,...

Read the Glaucoma article »



Read What Your Physician is Reading on eMedicine

Glaucoma, Low Tension »

Low-tension glaucoma (LTG) is a chronic optic neuropathy that affects adults.

Read More on eMedicine »

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