- An instrument for determining pressure or tension, especially an instrument for determining ocular tension.
- A vessel for equilibrating a liquid (blood) with a gas, usually at a controlled temperature; originally so named because it was used with a low 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 high gas:blood ratio to adjust the blood to the oxygen pressure of the gas.
[tono- + G. metron, measure]
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Examples: glitazone, GI cocktail, etc.