Definition of tonometer in US English:



  • 1A tuning fork or other instrument for measuring the pitch of musical tones.

  • 2An instrument for measuring the pressure in a part of the body, such as the eyeball (to test for glaucoma) or a blood vessel.

    • ‘Proper intraocular pressure is confirmed with the tonometer, which is removed and replaced with the suction ring/microkeratome track unit.’
    • ‘It is imperative to understand the effect of enteral feeding on measurements obtained via a gastric tonometer so that nutritional support can be optimized when this monitoring technique is used.’
    • ‘A blue light from the head of the tonometer is then held against the eye to measure pressure in the eye.’
    • ‘Using the slit lamp, your doctor moves the tonometer to touch your cornea.’
    • ‘Sometimes the tonometer is placed directly against the eyeball and pressure is applied in order for a reading to be taken.’


Early 18th century: from Greek tonos (see tone) + -meter.