Glaucoma is a disease that harms the eye’s optic nerve. This nerve sends light signals to the brain so eyesight can happen. Glaucoma happens when fluid builds up in the front part of the eye. This raises pressure in the eye and harms the nerve. This can cause eyesight problems and blindness.


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Common types of glaucoma are:

  • Open-angle happens when the eye does not drain fluid as well as it should. This slowly raises pressure in the eye. This is the most common type.
  • Angle-closure happens when the colored part of the eye (iris) blocks fluid from draining. This traps fluid in the eye and raises pressure. In some people, a sudden increase in pressure can cause blindness if it is not treated right away.
  • Normal-tension is when the nerve is harmed even though eye pressure is not raised.
  • Congenital happens at birth or within the first few years. It is often connected to other problems in the eye that slow fluid from draining.
  • Secondary can happen due to another health problem, such as a tumor, diabetes, or eye injury.

Angle-closure glaucoma. EBSCO DynaMed website. Available at: Updated October 24, 2016. Accessed April 29, 2020.

Facts about glaucoma. National Eye Institute website. Available at: Updated March 11, 2020. Accessed April 29, 2020.

Primary open-angle glaucoma. EBSCO DynaMed website. Available at: Updated February 7, 2020. Accessed April 29, 2020.

Prum BE Jr, Rosenberg LF, et al; American Academy of Ophthalmology. Primary Open-Angle Glaucoma Preferred Practice Pattern Guidelines. Ophthalmology. 2016 Jan;123(1):P41-P111.

What is glaucoma? American Academy of Ophthalmology website. Available at: Updated August 28, 2019. Accessed April 29, 2020.

What is glaucoma? Glaucoma Research Foundation website. Available at: Accessed April 29, 2020.

Last reviewed February 2020 by EBSCO Medical Review Board Daniel A. Ostrovsky, MD  Last Updated: 4/29/2020