The “puff of air” eye test, formally known as Non-Contact Tonometry (NCT), is a common and quick procedure performed during routine eye examinations. This rapid and non-invasive test uses a gentle burst of air to gather information about your eye health.
The Test’s Primary Purpose
The primary purpose of Non-Contact Tonometry is to measure your intraocular pressure (IOP), the fluid pressure inside your eye. This measurement helps eye care professionals screen for glaucoma, a condition where elevated IOP can damage the optic nerve, potentially leading to permanent vision loss.
Pressure builds when aqueous humor, a clear fluid in the front of the eye, cannot drain properly. This increased pressure can then press on the optic nerve, which transmits visual information to the brain. Early detection of elevated IOP is important because glaucoma often progresses without noticeable symptoms until significant damage has occurred. Regular monitoring of IOP allows for timely intervention to help preserve vision.
How the Test is Performed
You will rest your chin on a support and your forehead against a strap, aligning your eye with the machine. The device then directs a gentle puff of air at your cornea, the clear front surface of your eye.
The machine measures how your cornea responds to this air puff, specifically the time and force required to temporarily flatten it. Based on these measurements, it calculates your intraocular pressure. This method requires no physical contact with your eye and no numbing eye drops.
Understanding Your Results
Your intraocular pressure (IOP) readings are measured in millimeters of mercury (mmHg). A normal range for eye pressure is between 10 mmHg and 21 mmHg. Readings consistently above 21 mmHg may indicate ocular hypertension, meaning the pressure inside your eye is higher than normal.
An elevated reading does not automatically mean a glaucoma diagnosis. Ocular hypertension is a risk factor, but other factors also contribute, such as the appearance of the optic nerve and visual field test results. Your eye care professional will consider all these elements for a comprehensive assessment.
What to Expect and Next Steps
The non-contact tonometry test is painless and quick, taking only a few seconds per eye. You will feel a light puff of air, but it causes no discomfort. This makes it a preferred method for initial screening and for sensitive patients.
If an elevated IOP is detected, your eye care professional will discuss further diagnostic tests. These may include applanation tonometry, which involves gentle contact with the eye after numbing drops, or a visual field test to check your peripheral vision. An examination of your optic nerve will also be conducted to determine the next appropriate course of action for your eye health.