noun. a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists.
- dioptre (French)
- dioptra (Latin)
Example sentences of the word diopter
1. Noun, singular or mass
The amount the light is bent by one diopter amounts to an increase of 25 percent in the size of the viewed object.
2. Verb, base form
The power refers to diopter, which is a measure of the refractive strength of a lens or of an eye.