What do you need to know about ocular tonometry?
Tonometry is a diagnosis test that measures the pressure inside the eye, which is called intraocular pressure. This measurement can help your doctor determine whether or not you are at risk of glaucoma. Glaucoma is a severe eye disease that can eventually lead to vision loss if left untreated. In most cases of glaucoma, the fluid that normally bathes and nourishes the eye drains too slowly, causing pressure to build up. Without treatment, the increased pressure can eventually damage the optic nerve and cause vision loss.
The changes caused by glaucoma are often painless and can go on for years without being noticed.
A tonometry test is essential for early detection of the changes.
Tonometry is an ocular test that can detect changes in eye pressure long before you are aware of them. The most common type of tonometry test is called the “Goldmann applanation tonometry test”.
There are several other methods for testing eye pressure. These include an alternative type called non-contact tonometry, as well as the use of Tono-Pen and iCare tonometers. These tests are usually considered less accurate than Goldmann applanation tonometry. In non-contact tonometry, air pressure is applied to your eye using an instrument that gently flattens
What does ocular tonometry involve?
Before the tonometry test, the doctor will put eye drops in your eye so you won’t feel anything touching it. Once your eye is numb, your doctor may touch the surface of your eye with a small strip of paper, which has an orange substance, to stain it. This helps increase the accuracy of the test. Your doctor will then put a device called “slit lamp” in front of you.
It will ask you to place your chin and forehead on the holders provided, then move the lamp towards your eye until the tip of the tonometer probe touches your cornea. By flattening your cornea a little, the tonometer
can detect the pressure in your eye. The doctor will adjust the pressure until it obtains an accurate reading.
Because your eye is numb, you won’t feel pain during this procedure. Tonometry is a safe procedure.
What can be diagnosed by ocular tonometry?
Your doctor may suggest a tonometry test if he or she suspects you may be at risk of glaucoma, or to supplement some investigations.
You may have an increased risk of glaucoma if:
- you are over 40 years old
- have a family history of glaucoma
- you have myopia or hypermetropia
- have other chronic eye disorders
- have you injured your eye in the past
- you have diabetes
- have high blood pressure
- you have poor blood circulation
- you have used corticosteroid medicines for long periods of time
Your doctor may also test your eye pressure if you have symptoms such as:
- gradual loss of peripheral vision
- tunnel vision
- severe eye pain
- blurred vision
- haloes around lights
- reddening of the eyes
All these symptoms can be signs of glaucoma.