A Tonometry test is a quick and simple diagnostic procedure used to measure the fluid pressure inside your eye, known as intraocular pressure (IOP). This measurement is a critical part of a comprehensive eye exam and is the primary method for screening for glaucoma. At Pristine Eye Hospitals, we use advanced tonometry to safeguard your vision.
What is a Tonometry (Eye Pressure Test)?
Tonometry is a non-invasive diagnostic technique that determines your intraocular pressure. The test works by measuring the resistance of your cornea to a gentle force. This can be done in two common ways: the non-contact “air puff” method, which uses a brief puff of air to flatten the cornea, or the Goldmann Applanation Tonometer (GAT), which involves a small, flat-tipped probe that gently touches the surface of the anesthetized eye. Both methods provide your ophthalmologist with an accurate pressure reading, measured in millimetres of mercury (mmHg).
Why is this test performed?
This essential test is performed for several key reasons, including:
Screening for Glaucoma: High eye pressure is a major risk factor for glaucoma, a condition that can cause irreversible vision loss if left untreated.
Monitoring Glaucoma Treatment: For patients diagnosed with glaucoma, regular tonometry helps doctors assess the effectiveness of their treatment plan (e.g., eye drops or surgery).
Routine Eye Health Assessment: It is a standard component of a comprehensive eye examination for adults, especially those with risk factors like a family history of glaucoma, diabetes, or advanced age.
Evaluating Eye Trauma: After an eye injury, tonometry helps check for pressure changes that could indicate internal damage.
How to Prepare for Your Tonometry (Eye Pressure Test)
There is very little special preparation required for a tonometry test. It’s a quick, in-office procedure that is performed as part of your regular eye check-up. However, it is helpful to:
Inform your doctor about any prescription or over-the-counter eye drops you are currently using.
Remove contact lenses before the test, as they can interfere with the accuracy of the reading.
Mention if you have a history of corneal ulcers, infections, or a known allergy to anesthetic eye drops.
The Procedure: What to Expect Step-by-Step
The tonometry procedure is straightforward and takes only a few minutes.
1. Positioning: You will be seated comfortably and asked to place your chin and forehead on the supports of a specialized microscope called a slit lamp.
2. Anesthesia (for Goldmann method): If the contact method is used, the technician will administer a numbing eye drop so you won’t feel the instrument touch your eye. A harmless yellow dye may also be used to help with visualization.
3. Measurement: You will be asked to stare straight ahead at a target. For the air-puff test, a small puff of air will be directed at your eye for a fraction of a second. For the Goldmann test, a small probe will gently and briefly touch the surface of your cornea to take the measurement.
4. Completion: The process is repeated for the other eye. The numbing drops wear off within 15-20 minutes, and there are no lasting side effects.
Understanding Your Results
The results of your tonometry test are available immediately. Eye pressure is measured in millimetres of mercury (mmHg), and a normal range is typically considered to be between 12 and 22 mmHg. It is important to remember that this range is just a guideline.
A reading above 22 mmHg may indicate a higher risk for glaucoma, but it does not automatically mean you have the disease. Conversely, some people can develop glaucoma even with “normal” pressure levels (a condition known as normal-tension glaucoma). Your ophthalmologist at Pristine Eye Hospitals will interpret your tonometry results in conjunction with other diagnostic tests, such as an OCT scan and a visual field test, to get a complete picture of your eye health.
Frequently Asked Questions
Is the tonometry test painful?
No, the test is not painful. The air puff may be surprising, but it doesn’t hurt, and for the contact method, numbing eye drops are used to ensure you feel no discomfort.
How long does the test take?
The measurement itself takes only a few seconds for each eye. The entire process, including positioning and instruction, is typically completed in under five minutes.
Will my vision be blurry after the test?
The numbing drops used for Goldmann tonometry do not typically cause blurry vision and wear off quickly. Unlike dilating drops, they do not affect your ability to see clearly, so you can usually drive home afterwards.