Question: What is a diopter?
Answer: Optometrists measure refractive error in terms of diopters. Your eyeglass prescription is a measurement of your refractive error, or the degree from which you do not have normal vision. Prescriptions are commonly measured in units called diopters. A diopter is usually represented by a capital "D" in the prescription.
Diopters represent the level of correction you need in your eyeglasses or contact lenses to achieve normal vision. The higher your prescription in diopters, the more nearsighted or farsighted you are. Put simply, a prescription for higher diopter correction means you need more power in your lenses to bring vision back to a normal state.
