Tonometry

Glaucoma Screening Test

What To Think About

• Tonometry tests may be done over months or years to check for glaucoma. Also, because intraocular pressure (IOP) can change at different times of the day, tonometry is not the only test done to check for glaucoma. If the IOP is high, more tests, such as ophthalmoscopy, gonioscopy, and visual field testing, may be done. For more information, see the medical tests Ophthalmoscopy, Gonioscopy, and Vision Testing.
• Pachymetry uses ultrasound to measure the thickness of the cornea. The thickness of the cornea can affect IOP measurement. Pachymetry is often done during a tonometry test. It can help your doctor know your chance for developing glaucoma.
• Normal IOP is different from person to person. About 40% to 50% of people who have optic nerve damage caused by glaucoma have normal IOP.^{1, 2} In some cases of glaucoma there is damage to the optic nerve even though the eye pressure is never above normal.

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Author:	Jeannette Curtis	Last Updated: April 8, 2008
Medical Review:	Kathleen Romito, MD - Family Medicine Christopher J. Rudnisky, MD, FRCSC - Ophthalmology
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