1. An instrument for determining pressure or tension, especially an instrument for determining ocular tension. 2. A vessel for equilibrating a liquid ( e.g., blood) with a gas, usually at a controlled temperature; originally so named because it was used with a very small gas/blood ratio to allow the gas to approach blood oxygen tension and thus serve as a measure of it; now commonly used with a very large gas/blood ratio to adjust the blood to the oxygen pressure of the gas. SYN: aerotonometer (2). [tono- + G. metron, measure]
- applanation t. an instrument for determining ocular tension by application of a small, flat disk to the cornea.
- Gärtner t. an apparatus for estimating the blood pressure by noting the force, expressed by the height of a column of mercury, needed to arrest pulsation in a finger encircled by a compressing ring.
- Goldmann applanation t. an applanation t. that flattens only 3 mm2 of cornea, used with a slitlamp.
- Mueller electronic t. a Schiötz-type t. that electronically indicates the extent of corneal indentation; may also have an attached recorder for continuous pressure readings (tonography).
- Schiötz t. an instrument that measures ocular tension by indicating the ease with which the cornea is indented.
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to·nom·e·ter tō-'näm-ət-ər n an instrument for measuring tension or pressure and esp. intraocular pressure
to·no·met·ric 'tō-nə-'me-trik, .tän-ə- adj
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n.
1. (ophthalmotonometer) a small instrument for measuring the pressure inside the eye. There are several types. The applanation tonometer measures the force required to flatten a known area of the cornea after a drop of local anaesthetic has made the cornea numb. A greater force is required when the pressure inside the eye is increased, and vice versa. The Goldmann applanation tonometer flattens a corneal area of 3 mm2.
2. an instrument for measuring pressure in some other part of the body.
• tonometry n.
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to·nom·e·ter (to-nomґə-tər) [tono- + -meter] 1. an instrument for measuring tension or pressure. 2. specifically, an instrument by which intraocular pressure is measured.Medical dictionary. 2011.