Definition of dioptre in English:


Line breaks: di|optre
Pronunciation: /dʌɪˈɒptə
(US diopter)


  • A unit of refractive power, which is equal to the reciprocal of the focal length (in metres) of a given lens: vision corrected to within one dioptre of perfect sight
    More example sentences
    • The focusing power of a lens is measured in dioptres.
    • Refractive error is measured in dioptres, and myopia is designated with a minus sign.
    • The difference between the focusing powers of these two axes, measured in dioptres, is the astigmatism.


late 16th century (originally as diopter, denoting an alidade): from French, from Latin dioptra, from Greek, from di- 'through' + optos 'visible'. The term was used in the early 17th century to denote an ancient form of theodolite; the current sense dates from the late 19th century.

More definitions of dioptre

Definition of dioptre in:

Get more from Oxford Dictionaries

Subscribe to remove adverts and access premium resources

Word of the day kerf
Pronunciation: kəːf
a slit made by cutting with a saw