During Your Eye Exam: How the Glaucoma “Puff” Works

There’s one assessment at the optometrist’s office that makes me feel a little nervous…the “air puff” to check for glaucoma. Don’t get me wrong. The test takes just a few seconds from start to finish, and it doesn’t hurt at all! But sitting, waiting, and anticipating when that air puff will come–all without blinking–challenges me. I have to concentrate very hard to keep my eyes from shutting! The test, called the non-contact tonometry test (or “NCT”), is the simplest way for your eye care provider to test for glaucoma.

Here’s how it works

The first thing you do is position your head correctly for the machine to accurately deliver the puff of air. To do this, you set your chin in the designated chin rest and position your forehead against another designated rest. Once your head is positioned correctly, the technician will adjust the machine so your eyes are aligned correctly. A red or green light will guide your gaze to the right spot. Once you find it, the technician will let know your head is positioned properly.

Once you’re positioned correctly, the technician will trigger the machine and you’ll receive the quick puff of air. What do we mean by a “puff”? The NCT sends what feels like a gentle “blow” of air right into your open eyeball. Nothing actually touches your eye, other than the air, and it doesn’t hurt at all.

Assuming you don’t blink during this process (It can sometimes be hard to keep your eye open during the puff!), the machine calculates the pressure inside your eye, also called intraocular pressure (IOP).

older man with glassesDetermining Intraocular Pressure

The machine is able to determine your IOP based on your eye’s resistance to the puff of air. If you have high eye pressure, you may be at risk for or have glaucoma. Glaucoma is kind of like high blood pressure for your eyes. Just like high blood pressure throughout your body can cause all sorts of physical problems, glaucoma can cause gradual loss of sight and eventual blindness.

A normal reading of eye pressure is 12-22 mm HG. This stands for millimeters of mercury. The higher your reading, the higher the pressure in your eye. That also means there’s a higher chance that your optic nerve could be damaged.

If you do have a high reading after the NCT machine test, your optometrist may recommend prescription drops or may send you to an ophthalmologist to discuss surgical options for relieving the intraocular pressure. Though glaucoma can’t be cured, it can be controlled. This is why early detection, intervention and regular, comprehensive eye exams – including the “air puff” test – are so important.

Have other questions about glaucoma or glaucoma testing? Read more on our website or schedule an appointment to talk to your Eyeglass World optometrist.