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 flatten (flatten) the cornea. Corneal flattening is detected by an electro-optical system. Intraocular pressure is estimated by detecting the force of the air jet at the time of flattening. Historically, non-contact tonometers were not considered an accurate way to measure IOP, but rather a quick and easy way to detect high IOP. However, modern non-contact tonometers have been shown to correlate well with Goldmann tonometry measurements and are particularly useful for measuring IOP in children and other patient groups.