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Intraocular Pressure and Glaucoma

Intraocular pressure (IOP) is the pressure caused by the fluid inside the eye that helps maintain the shape of the eye. The level of pressure inside the eyes depends on:

  • How much fluid is produced inside the eye.
  • Whether fluid can travel normally through the eye.
  • How well the fluid is removed from the eye.

The pressure within the eyes varies during the day. Normally, the pressure inside the eye ranges from 10 millimeters of mercury (mm Hg) to 21 mm Hg.

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  • Intraocular pressure can vary from person to person.
  • Not all people with open-angle glaucoma (OAG) have increased pressure inside the eye. As many as 40% to 50% of cases of OAG may occur without increased pressure inside the eye, and most people with elevated pressures will never get glaucoma.1, 2


  1. Shah R, Wormald R (2009). Glaucoma, search date November 2007. Online version of BMJ Clinical Evidence:

  2. Trobe JD (2006). Principal ophthalmic conditions. Physician's Guide to Eye Care, 3rd ed., chap. 6, pp. 107-111. San Francisco: American Academy of Ophthalmology.

By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer Christopher J. Rudnisky - Ophthalmology
Last Revised May 5, 2010

WebMD Medical Reference from Healthwise

Last Updated: May 05, 2010
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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