dioptre

British  

/ daɪˈɒptə /

noun

1. a unit for measuring the refractive power of a lens: the reciprocal of the focal length of the lens expressed in metres

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Other Word Forms

• dioptral adjective

Etymology

Origin of dioptre

C16: from Latin dioptra optical instrument, from Greek, from dia- through + opsesthai to see

Example Sentences

But on average, the difference between dropping out at 16 and staying on until the end of university is "minus one dioptre".

From BBC

Enough, we must not over-rate the value of the objective determination of the error of refraction, and I would estimate the limit of error at half a dioptre at least.

From Project Gutenberg

Opticians measure the ability of your eye to focus light in dioptres.

From BBC

Minus one dioptre is relatively mild, but it's enough to need glasses for driving.

From BBC

Isler found in hypermetropia of 2 to 10 dioptres squinting in 75 per cent.; in my statistics H. 1·5 D. to the highest degrees of hypermetropia are likewise represented by 75 per cent.

From Project Gutenberg