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

In mydriasis by atropine hypermetropia of 3 to 4 dioptres results.

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

Patient really comes on account of his son, aged 7-1/2, in whom hypermetropia of 3·5 dioptres is detected with the ophthalmoscope, right eye with + 3·5 V. 5/9.

From Project Gutenberg