A tonometer is an instrument for measuring tension or eye pressure. Tonometry is the procedure which your doctor performs to determine the intraocular pressure (IOP), the fluid pressure inside the eye. It is an important test in the evaluation of patients with glaucoma.

Non-contact tonometry (or air-puff tonometry) is different from pneumatonometry and was invented by Bernard Grolman of Reichert, Inc (formerly American Optical). It uses a rapid air pulse to applanate the cornea. This special piece of equipment is particularly useful for measuring IOP in children and is accomplished without the instrument contacting the cornea.