1. A unit of measurement of the refractive power of a lens, equal to the reciprocal of the focal length in meters.
Usage: optics; commonly used in eyeglasses and contact lens prescriptions

Examples

• The prescription for her glasses was +2.5 diopters in each eye.
• A lens with a focal length of one meter has a refractive power of one diopter.
• Contact lens prescriptions are measured in diopters.
• The stronger the diopter value, the more the lens bends light.
• His myopia required a correction of -3.0 diopters.