What is non-contact tonometry?
Non-contact tonometry (the 'air-puff' test) measures intraocular pressure (IOP) using a gentle pulse of air, without any instrument touching the eye. Raised eye pressure is an important early warning sign of glaucoma.
Comfortable and instant
There is no need for numbing drops and nothing touches your eye. You feel only a brief puff of air, and the result is available in seconds, making it ideal for routine screening.
What is the full form of NCT?
NCT stands for Non-Contact Tonometry. It is the air-puff test that measures the pressure inside your eye, the intraocular pressure (IOP), without anything touching the surface of the eye. The word 'tonometry' simply means the measurement of eye pressure, and 'non-contact' refers to the no-touch, air-based method used.
How the NCT machine works: the air-puff principle
The instrument that performs this test is called a non-contact tonometer. It releases a brief, calibrated puff of air at the front of the eye, which momentarily flattens a tiny area of the cornea. A built-in optical sensor measures how the cornea responds to that puff, and the machine uses this to estimate your eye pressure. The whole process takes only a moment and needs no numbing drops, because nothing physically touches the eye.
NCT in a routine eye check-up
The air-puff test is a standard part of a comprehensive eye examination at many clinics. Because raised eye pressure often causes no symptoms in its early stages, NCT is used to screen for glaucoma so that any concern can be picked up early. It is fast, comfortable and easy to repeat, which makes it well suited to routine check-ups. If the reading is high or borderline, your doctor may follow up with more detailed pressure testing.
NCT vs contact (applanation) tonometry
Non-contact tonometry uses a puff of air and is mainly a quick screening tool, while contact (applanation) tonometry gently touches the cornea with a small probe after numbing drops. Goldmann applanation tonometry is regarded as the clinical reference standard for measuring eye pressure and is often used when a precise reading is needed, such as in the diagnosis and ongoing management of glaucoma. In practice, NCT is commonly used first for screening, and applanation may be used to confirm or monitor pressure. Your doctor decides which method is most appropriate for your situation.