Tonometry tests the amount of pressure in the eye. This is known as intraocular pressure (IOP).
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.
There are no major complications associated with this procedure.
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.
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.
You will be asked to look into an instrument. A puff of air will be blown into the eye.
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.
The numbing drops and dye wear off in about 20 minutes. The eye should not be rubbed during this time. It may cause damage.
A few seconds
This test should be painless. Some people have a slight sting from the eyedrops.
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.
After the test, call your doctor if you have:
If you think you have an emergency, call for medical help right away.
Glaucoma Research Foundation
National Eye Institute
Canadian Association of Optometrists
Canadian Ophthalmological Society
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