diopter

noun

di·​op·​ter dī-ˈäp-tər How to pronounce diopter (audio)
ˈdī-ˌäp-
: a unit of measurement of the refractive power of lenses equal to the reciprocal of the focal length in meters

Examples of diopter in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Our tester found the twist-out eyecups and diopter worked well, but the objective lens caps were a tight fit. — Scott Gilbertson, WIRED, 6 Oct. 2024 Current Clinical Trials and Outcomes Clinical trials have started on the effectiveness of spiral diopter lenses for correcting presbyopia. — William A. Haseltine, Forbes, 26 Feb. 2024

Word History

Etymology

diopter (an optical instrument), from Middle French dioptre, from Latin dioptra, from Greek, from dia- + opsesthai to be going to see — more at optic

First Known Use

circa 1864, in the meaning defined above

Time Traveler
The first known use of diopter was circa 1864

Browse Nearby Words

dioptase
diopter
dioptral
See all Nearby Words

Cite this Entry

“Diopter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/diopter. Accessed 28 Apr. 2025.

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Medical Definition

diopter

noun
di·​op·​ter
variants or chiefly British dioptre
dī-ˈäp-tər, ˈdī-ˌäp- How to pronounce diopter (audio)
: a unit of measurement of the refractive power of a lens equal to the reciprocal of the focal length in meters

More from Merriam-Webster on diopter

Britannica.com: Encyclopedia article about diopter

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