Tonometry Test Explained: Eye Pressure Screening and Glaucoma Assessment

Tonometry is an eye evaluation that measures eye pressure. It's one of the main tests for glaucoma. There are many techniques for early tonometry, all of which are quick and painless. This test can detect alterations to eye pressure far ahead of the person noticing them.

The word tonometry is derived from the Greek words tonos "tension" and metron "measure". It means the measurement of tension or pressure. This is where we can successfully measure intraocular pressure, an important parameter that defines the eye's health.

Also, viewed as the international yardstick for measuring eye pressure over several decades, it employs a flat-tipped probe for a gentle push against the eye surface. Tonometry is a very reliable method to get done if you suspect glaucoma and could save your eyes from such a terrible issue.

What is Tonometry and who needs this test?

According to the American Academy of Opthalmology (AAO), ‘’Tonometry is an eye pressure test that measures the pressure inside the eye, also known as intraocular pressure (IOP)’’. This pressure is an important factor concerning the health and function of an eye. 

Many people are not aware of the gradual change in their eye pressure which could eventually lead to Glaucoma, a condition with an increased eye pressure, eventually leading to vision loss.

That is when tonometry comes in to save you from such grave eye problems. If you suspect any such issues, waste no time to visit your eye doctor. 

According to your eye doctor, you may possibly be required to undergo the Goldman applanation tonometry test for diagnosis of conditions said to be cause for the test. 

The applanation test may also be affected by floating and suspending the results of another eye test, which signals a potential problem in your eyes. 

As noted by the AAO, acute risks for glaucoma are among:

• Most are older than 40 years old 
• Being Black, Hispanic, or Asian
• Family history of glaucoma
• Being near or away vision
• Any other chronic eye disease
• Eye injury previously
• Diabetes
• Hypertensive
• Poor blood circulation
• Using corticosteroid drugs for long periods 

After your doctor takes a look at you, he might also measure your eye pressure if you have symptoms like: 

• Progressive loss of peripheral vision
• Tunnel vision
• Intense pain in the eye
• Blurred vision 
• Halos surrounding lights
• The reddish appearance of your eye

What is glaucoma and when is a tonometry test needed?

Many severe forms of blindness are avoidable with timely treatment of glaucoma. Many types of glaucoma have slow drainage of the natural aqueous fluid that nourishes the eye. That, then, builds up pressure within the eye.

Damage can occur to the optic nerve if untreated increased pressure finally causes the nerve to die, leading to blindness.

According to the American Academy of Ophthalmology (AAO), cases such as these could lead to blindness as a common cause of glaucoma among adults aged above 60 years. 

These modifications due to glaucoma are typically painless and gradual for years without realizing them; hence, tonometry is crucial in its early detection. If any of your test results are abnormal, your eye doctor will surely want to conduct additional tests to confirm the disease.

Tonometry is for screening and diagnosis of glaucoma utilized primarily by eye care practitioners including fellow ophthalmologists and optometrists. It forms a routine part of the eye examination but is also relevant to specific examinations on cases suspicious of ocular injuries and signs and symptoms involving doctors. It is also used by eye specialists in monitoring your eye pressure if you are taking certain medications.

Keeping track of your pressures is a primary method to ensure that treatment is working, so tonometry could be used regularly in a lot of cases-including with devices you can use at home to take readings on yourself. If you have glaucoma, routine tonometer measurements inform treatment.

What is involved during a tonometry test?

Before the Goldmann tonometry test, the eye doctor puts an anaesthetic drop in the patient in his eyes so that no feeling is experienced while putting any instrument in the eye.

Then, the eye will receive a dab of a small paper strip containing an orange dye that your doctor may apply to the surface of your eye to stain, which also improves the accuracy of the test.

Your doctor will then ask you to rest your chin and the forehead on the frame supports and then bring the slit-lamp machine towards your eye until the tip of a tonometer probe touches the area of your cornea.

By just flattening your cornea a bit, a tonometer is able to read the pressure in your eye. Your eye doctor will adjust the tension until they get a proper reading. It doesn't hurt at all because the eye is numb during the process.

Tonometry is very safe, though it carries a very small risk of scratching your cornea with the tonometer making contact with your eye. But in case this should happen, be very certain that your eye will usually heal within a couple of days.

What are the different types of tonometry tests?

Your eye care specialist can perform tonometry using the following methods:

1. Applanation tonometry

Applanation means "flattening," and so devices using it have a small disk-like extension that rests against the surface of your eye. They measure the amount of force required to start flattening your eye surface.

This is the most accurate method. It is conventionally used by eye specialists when other methods give abnormal or alarming results.

2. Continuous monitoring

This one uses a sensor that you wear on the eye like a contact lens. It is being investigated by researchers into the other kind that uses a surgically implanted sensor.

3. Dynamic contour tonometry

They have a small, sensor-tipped extension that touches your eye but does not make an indention.

4. Electronic indentation tonometry

Devices using this method would have a small probe that takes a measurement when it presses against the surface of your eye enough to make a small indention.

5. Non-contact tonometry

 Devices that employ this method blow air at your cornea. It will then measure very small, split-second changes in the configuration of your cornea once the air has bounced off its surface. Air puff tonometers do this with a small puff of air, while ocular response analyzers use a stream of air.

What to expect before, during, and after the test?

How should I prepare for a tonometry test?

Preparation is rarely needed for a tonometric test. Only when there's a tight collar should you take care not to wear this during the test (whether it requires wearing another shirt or loosening the collar if possible). Pressure around your neck from your clothes can increase your intraocular pressure readings.

What can I expect during the tonometry tests?

What you can expect of tonometry will vary by method. With applanation tonometry, he'll put anaesthetic eye drops and dye (called fluorescein) in your eyes. Non-contact tonometry and most methods don't need that, either.

With most methods of tonometry, the test is only a matter of seconds. Many of these faster methods are meant to be averaged over several readings, so don't be surprised or think that something has gone wrong if your eye specialist wants to retake the readings a few times. 

Some methods (for example, applanation tonometry) may last a couple of minutes. More information will be provided to you by your eye specialist regarding what to expect during the test.

What should I expect after the test?

The tonometry results are instant. For the first few hours, you have to be very careful about not letting anything touch your eyes until the anaesthetic wears off. Anaesthetic eye drops prevent the sense of pain, so much injury can occur to the eyes when they are numb.

What do the test results indicate?

Eye pressure is interpreted in clinical context. Although a statistical reference range is often discussed, glaucoma can occur at lower pressures and some people with higher pressure do not have glaucoma. A pressure reading alone cannot diagnose or exclude the disease.

If the results are too high

If simpler eye tests give a high-pressure reading, your specialist will probably recommend applanation tonometry to confirm the results. If that confirms that your readings are high, treatment options will be discussed with close monitoring. Their recommendation is to have follow-up visits as needed.

Home pressure monitoring is used only in selected cases under professional guidance. Do not interpret a single reading or change treatment without instructions from the treating clinician.

The urgency of an abnormal reading depends on symptoms, the measured pressure, optic-nerve findings and other clinical factors. Follow the clinician’s advice; severe eye pain, red eye, headache, nausea, halos or sudden vision change requires urgent ophthalmic or hospital assessment.

Acute angle-closure glaucoma is an emergency that can threaten vision. Seek urgent ophthalmic or hospital care for severe eye pain, red eye, headache, nausea, halos or sudden blurred vision.

The other next steps will depend on your particular situation and needs. Your eye specialist could inform you about what to expect for your particular case.

If your results are lower

Low levels of intraocular pressure, usually below 5 mmHg or sometimes below 6 mmHg, are also a cause for concern as they can result in damage to and loss of vision. If the intraocular pressure is too low in your finding, your eye specialist shall discuss treatment options with follow-up visits to maintain intraocular health.

Can I drive after a tonometry test?

You may be able to drive following an eye pressure check depending on some factors. A major one is whether the eye exam involved dilation of the eyes (which generally takes place after tonometry during a routine eye test). 

While dilating your eyes would make them sensitive to light and sometimes make focusing and reading up close difficult, there are times this effect lasts anywhere from a few to several hours. Eye specialists also provide a number of disposable shades that may be worn after examination; these shades easily fit over eyeglasses too, if you have them. 

These shades help induce brightness and glare such that one feels comfortable seeing a bit clearer. And many people believe they can still drive after eye dilation. If you have any doubts about whether you can legally drive after an eye examination, consider arranging your transport to and from the visit to your eye specialist.

Conclusion

You probably don't anticipate the blowing device or holding something close to your eyes, but it is for a good reason. Glaucoma is a very common eye issue. However, the increased pressure in your eye causing it can usually be detected long before any symptom or permanent damage develops. 

If it turns out that you have high pressure inside your eyes, our eye specialist here at Vision Concern will be able to help. Our professional support might just be what makes the pressure more tolerable within your otherwise exquisite eyes. And that might bring relief to the anxiety you feel regarding eye health as well.

FAQs

1. Is tonometry painful?

Ans: Though tonometry is probably going to involve some sort of contact with the eyeball, it shouldn't hurt. If you do experience any pain or discomfort, do not keep quiet. Ask your doctor what is happening and ask for more information about what to expect from the pain. For eg: how long it is likely to last and what you can do about it.

2. How does tonometry work?

Ans: The procedure of tonometry is designed to measure the pressure inside the anterior chamber of your eye. The anterior chamber is the area filled with liquid located just behind your cornea at the front of your eye. This pressure from the aqueous humour liquid contained within that chamber allows your eyes to maintain their globe-like shape.

Authoritative Glaucoma and Eye-Pressure Reference

For patient information about eye pressure and glaucoma risk, see the National Eye Institute glaucoma and eye-pressure guide. A tonometry result alone does not diagnose or exclude glaucoma; interpretation may require a comprehensive examination and additional testing.