diopter
/daɪˈɑptər/
noun
- A unit of measurement for the focusing power of a lens, used especially for eyeglasses and contact lenses.
- A magnifying glass might have a power of +3 diopters.
- My new glasses have a strength of -2.5 diopters.
- The optician said my prescription changed by half a diopter.
- A device or adjustment on an optical instrument (like a telescope or camera) that helps focus the view for the user's eyesight.
- He set the diopter on the microscope to match his vision.
- I turned the diopter on the binoculars until the image was sharp.
- The camera's viewfinder has a diopter adjustment for people who wear glasses.