tonomeetria

Tonometry is a group of methods for measuring pressure in a closed space or vessel. In medicine it commonly refers to intraocular pressure measurement for glaucoma screening and to arterial tonometry, a noninvasive technique to estimate arterial pressure waveforms and central blood pressure.

Ophthalmic tonometry relies on the pressure required to deform or flatten a portion of the eye. Indentation tonometry uses a calibrated plunger to indent the cornea; applanation tonometry measures the force needed to flatten a corneal area; rebound tonometry uses a small probe that bounces off the cornea; non-contact tonometry uses an air puff to briefly flatten the cornea. Widely used ophthalmic tonometers include the Goldmann applanation tonometer, Tonopen, iCare rebound tonometer, and various air-puff devices.

Arterial tonometry records the pressure waveform at a superficial artery, typically the radial artery at the wrist, by sensing arterial deformation or applying a light touch with a sensor. The waveform is processed to estimate central (aortic) pressure and measures of arterial stiffness; this approach is common in research and some clinical settings.

Accuracy and limitations: Ophthalmic tonometry can be affected by corneal thickness and biomechanics; contact methods require topical anesthesia and careful technique; non-contact methods may be less precise in some patients. Arterial tonometry depends on correct calibration and operator skill and can be affected by irregular heartbeats or vascular disease.

History: Applanation tonometry, developed in the mid-20th century, improved accuracy over earlier indentation methods. Modern variants include rebound and non-contact devices.