The eye puff test, formally known as non-contact tonometry (NCT), is a common and non-invasive procedure performed during routine eye examinations. It serves as a quick assessment tool for eye health. This test is a standard component of a comprehensive eye screening, offering insights without direct contact.
Understanding the Eye Puff Test
The eye puff test, or Non-Contact Tonometry (NCT), measures the pressure inside your eye, known as intraocular pressure (IOP). This pressure comes from the aqueous humor, a clear fluid that fills the front part of the eye, nourishing structures like the lens and cornea. A balanced production and drainage of this fluid maintain a stable IOP. If the fluid drainage system does not function efficiently, fluid can accumulate, increasing intraocular pressure.
Measuring IOP is an important step in screening for glaucoma, a group of eye diseases that can damage the optic nerve. Elevated IOP can exert pressure on the optic nerve, potentially leading to damage and vision loss if untreated. While high IOP is a risk factor, it does not automatically diagnose glaucoma. The test helps identify individuals at increased risk, prompting further investigation.
How the Test is Performed
The non-contact tonometry procedure is quick and well-tolerated. You will sit with your chin on a rest and forehead against a support to stabilize your head. The eye care professional aligns the machine with your eye, and you look at a light or target inside the device. This alignment ensures an accurate measurement.
A brief, gentle puff of air is released onto your open eye. This puff momentarily flattens a small area of your cornea, the clear front surface of your eye. The machine measures the time and force required for this flattening to calculate your intraocular pressure. The sensation is often described as a mild surprise or a soft push, and it is over in a matter of seconds. No numbing eye drops are needed.
Interpreting Your Results
The eye puff test results are expressed in millimeters of mercury (mmHg), indicating intraocular pressure. A typical normal range for IOP is between 10 and 21 mmHg. Readings within this range are considered healthy, though individual variations can occur. Elevated pressure, defined as an IOP greater than 21 mmHg, is referred to as ocular hypertension.
An elevated reading from the eye puff test does not confirm a glaucoma diagnosis. Instead, it suggests a higher risk and indicates the need for additional, more definitive tests. These might include applanation tonometry, which involves gentle contact with the eye after numbing drops, or a thorough examination of the optic nerve and visual fields. Regular eye examinations are important for monitoring IOP over time, helping detect significant changes that warrant further evaluation.