Tonometry: Glaucoma Testing
Tonometry is a category of procedures and tests that are performed to asses the pressure inside your eyes. Elevated internal eye pressure can cause glaucoma, which is vision loss due to damage to the sensitive optic nerve in the back of the eye.
The most commonly used method tonometry is the famous "Air puff" test. During the Air Puff test a machine sprays a burst of air directly onto the surface of your eyeball. Based on your eye's resistance to the released puff of air, the instrument evaluates the pressure on the inside of your eye. This internal pressure is called your eye's intraocular pressure (IOP).
The procedure itself can be startling and many are adverse to having it performed, nothing but air touches the surface of your eye during this measurement. There's no risk of eye injury from the Air Puff test.
Another popular way to measure eye pressure is with an instrument called an applanation tonometer, which is usually attached to a slit lamp. For this test, a yellow eye drop is placed on your eyes. Your eyes will feel slightly heavy when the drops start working. This is not a dilating drop – it is simply a numbing agent combined with a yellow dye. Then the doctor will have you stare straight ahead in the slit lamp while he or she gently rests the bright-blue glowing probe of the tonometer on the front of each eye and manually measures the intraocular pressure.
Like the air puff test, applanation tonometry is painless and takes just a few seconds.
Because glaucoma is the result of an increase of intraocular pressure, the pressure inside your eye, these are important tests for ensuring the long-term health of your vision and eyes.