Tonometry

What is tonometry?

Tonometry is a quick test performed by your healthcare provider to measure the pressure inside your eyes.

What is tonometry used for?

Your healthcare provider uses ocular tonometry to see if you’re at risk for glaucoma. In people with glaucoma, the fluid that circulates inside their eye is either produced too fast or drains too slowly. As a result, the pressure inside their eye builds up. Left untreated, increased eye pressure can eventually impact the optic nerve and cause vision loss.

Who should have a tonometry test?

People who have a heightened risk of glaucoma should undergo a tonometry test. There are several factors that increase your risk for glaucoma, including:

• Family history.
• Age.
• Race.
• History of eye injuries.
• High blood pressure (hypertension).
• Diabetes.
• Migraine headaches.
• Thin corneas.

You should also schedule a consultation with your healthcare provider right away if you experience:

• Blurred vision.
• Severe or persistent eye pain.
• Tunnel vision.
• Halos around lights.
• Loss of peripheral vision.

Who performs tonometry tests?

Tonometry tests are performed by eye care professionals, such as optometrists and ophthalmologists.

How does tonometry work?

Ocular tonometry measures the pressure inside of your eye by flattening your cornea. The more force that’s needed to flatten your cornea, the higher the intraocular pressure. People with high intraocular pressure are more likely to develop glaucoma. Tonometry helps detect this problem early on so your healthcare provider can create an effective treatment plan.

What should I expect before my tonometry test?

Before performing your ocular tonometry test, your healthcare provider will put numbing eye drops in your eyes. This keeps you from feeling anything during the test.

How is tonometry performed?

Ocular tonometry may be performed using different methods, depending on your needs. No matter what type of tonometry test is used, the main goal is the same: to measure the pressure inside of your eye by applying force to your cornea.

What are the types of tonometry tests and how do they measure eye pressure?

Your provider can perform several different types of tonometry tests. Your healthcare provider will determine which assessment is best suited to your needs. Some of the most common types of tonometry include:

• Non-contact tonometry. Also known as air-puff tonometry, this test uses a puff of air to flatten your cornea. Non-contact tonometry isn’t the most accurate way to measure the pressure inside your eye. However, it’s commonly used as a simple screening tool and is the easiest way to test children.
• Applanation (Goldmann) tonometry. During this diagnostic assessment, your provider uses a small probe to flatten your cornea. They then use a slit lamp to examine your eye. Applanation tonometry is extremely accurate and is often performed after air-puff tonometry has detected high intraocular pressure.
• Electronic indentation tonometry. This type of tonometry test uses an electronic device to measure intraocular pressure. Your healthcare provider places a small instrument directly on your cornea and the test results are read on a computer screen.

Can you feel high eye pressure?

Unless the pressure is extremely elevated, there’s usually no way to feel if the pressure inside of your eyes is building up. That’s why routine eye exams are so important. Your healthcare provider can detect any problems and treat them before they worsen.

There are certain conditions that can cause the sensation of pressure behind your eyes. This includes headaches, sinus infections or toothaches.

Does a tonometer touch your eye?

Yes. Unless your healthcare provider is performing air-puff tonometry, an instrument will gently touch your eye during the assessment. You’ll be given numbing eye drops so you won’t feel anything.

What should I expect after a tonometry test?

Your healthcare provider will know your results immediately in most cases. If your results are abnormal, other tests will likely be performed to confirm your diagnosis.

Are there tonometry side effects?

No. There are no risks associated with having a tonometry test.

What is a tonometry normal range?

Normal eye pressure ranges from 10-21 mm Hg (millimeters of mercury. This refers to the units used to measure eye pressure.) If your eye pressure is higher than 21 mm Hg, then you could have pre-glaucoma or glaucoma.

Low eye pressure usually isn’t a cause for concern. However, the risk of blurred vision increases with eye pressures under 6 mm Hg.

When should I call my healthcare provider?

Tonometry doesn’t typically cause side effects. So if you notice any sudden changes in your vision — or if you’re having pain — contact your healthcare provider right away. They can perform further testing to determine the problem.

What’s the difference between tonometry and tomography?

Tomography is a type of digital imaging. In ocular health, tomography may refer to a cross-section of the retina or optic nerve. Tonometry, on the other hand, refers to the testing method used to measure the pressure inside of your eye.

A note from Cleveland Clinic

Tonometry is a simple and straightforward test that can tell you whether or not you’re at risk for glaucoma. Even though glaucoma can’t be cured, it can be successfully managed with proper treatment. If you notice any symptoms of glaucoma, like tunnel vision, blind spots, eye pain or blurred vision, schedule an appointment with your healthcare provider immediately. Prompt treatment can halt the condition in its early stages and dramatically improve your quality of life.