What is Primary Open-Angle Glaucoma?

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  • Written By: A.E. Freeman
  • Edited By: Melissa Wiley
  • Last Modified Date: 15 November 2018
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Primary open-angle glaucoma is the most common type of glaucoma. When a person has primary open-angle glaucoma, the eye cannot drain fluid properly and pressure builds up. The cause of this type of glaucoma is usually unknown. The build-up of pressure can lead to vision problems, including complete blindness, down the road.

Fluid known as aqueous humor normally leaves the eye in a drainage area between the iris and cornea. When a person has primary open-angle glaucoma, the trabecular meshwork, or small drainage channels located inside the drainage area between the iris and cornea, are blocked. As the fluid backs up within the eye, pressure builds, causing damage to the optic nerve.

Unfortunately, symptoms of primary open-angle glaucoma often do not appear until the disease has advanced and may not be reversed. A person may experience tunnel vision or a loss of peripheral vision, though usually it takes years for any vision loss to develop. Since primary open-angle glaucoma usually affects older people, those more than age 40 should get tested by an eye doctor every few years. People over age 60 should get tested yearly. If a person has a family history of glaucoma, he or she should get tested regularly starting at age 20.


The tests for primary open-angle glaucoma include a vision test, pachymetry, and tonometry. The vision test determines if a person has lost any peripheral vision. Pachymetry tests how thick a person's corneas are, which can affect the pressure in the eyes. If a person has thick corneas, he or she is more likely to have slight eye pressure than a person with thinner corneas. Tonometry is the test that measures the intra-ocular pressure. The doctor will use drops to numb a person's eyes during both pachymetry and tonometry. The tests can be performed in a single doctor's visit and do not cause any pain.

There are several treatments for primary open-angle glaucoma. Eye drops are usually the first treatment prescribed by a doctor. Drops that contain beta blockers, alpha-agonists, or carbonic anhydrase inhibitors reduce the amount of aqueous humor produced by the eye, while drops that contain prostaglandin-like or epinephrine compounds increase the amount of aqueous humor produced. Red and swollen eyes are a common side effect of the drops. Some people may experience more severe side effects throughout their bodies from using the eye drops. If eye drops are ineffective, glaucoma can be treated with oral medications. In some cases, laser surgery may be needed to open the drainage area.



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