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Tonometry

(Intraocular Pressure [IOP] Measurement)

Definition

Tonometry tests the amount of pressure in the eye. This is known as intraocular pressure (IOP).

Reasons for Test

Eye damage can happen when pressure in the eye is too high. This is called glaucoma.

This test is commonly used to screen for glaucoma. It is also used to see if glaucoma treatment is working.

Glaucoma
Glaucoma

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Possible Complications

There are no major complications associated with this procedure.

What to Expect

Prior to Test

The care team may ask about any medicines, herbs, and supplements that you take. You will also be asked to remove eyeglasses or contact lenses.

Description of the Test

There are two tonometry methods. Both flatten the layer on the front of the eye using gentle pressure. The type of tonometry that is done depends on the equipment your doctor has.

You will be asked to sit in an exam chair. A chin cup and forehead rest will steady your head.

Non-contact Method

You will be asked to look into an instrument. A puff of air will be blown into the eye.

Applanation Method or the Goldmann Tonometry

Numbing drops will be put in your eyes. A small amount of an orange dye drops may also be used to view the eye better. You will be asked to look into an instrument with a blue light. A tiny device will gently press against your eye.

A handheld device shaped like a pen may be used instead. It will be pushed against the front of your eye.

There are other devices that are used to check eye pressure. These are the most common.

After Test

The numbing drops and dye wear off in about 20 minutes. The eye should not be rubbed during this time. It may cause damage.

How Long Will It Take?

A few seconds

Will It Hurt?

This test should be painless. Some people have a slight sting from the eyedrops.

Results

A person having the test done to screen for glaucoma will talk to their doctor about whether treatment is needed.

A person having the test to monitor glaucoma will talk to their doctor about whether changes need to be made to their treatment plan.

Call Your Doctor

After the test, call your doctor if you have:

  • Burning
  • Excessive itching
  • Swelling
  • Pink or reddish color that does not go away
  • Problems seeing
  • Any other eye problem

If you think you have an emergency, call for medical help right away.

RESOURCES:

Glaucoma Research Foundation
http://www.glaucoma.org

National Eye Institute
http://www.nei.nih.gov

CANADIAN RESOURCES:

Canadian Association of Optometrists
http://www.opto.ca

Canadian Ophthalmological Society
http://www.eyesite.ca

REFERENCES:

Angle-closure glaucoma. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/angle-closure-glaucoma. Accessed December 11, 2020.

Five common glaucoma tests. Glaucoma Research Foundation website. Available at: http://www.glaucoma.org/glaucoma/diagnostic-tests.php. Accessed December 11, 2020.

Primary open angle glaucoma. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/primary-open-angle-glaucoma. Accessed December 11, 2020.

Tonometers. The College of Optometrists website. Available at: http://www.college-optometrists.org/en/college/museyeum/online_exhibitions/optical_instruments/tonometers.cfm. Accessed December 11, 2020.

Last reviewed September 2020 by EBSCO Medical Review Board Marcin Chwistek, MD  Last Updated: 4/23/2021