diopter

Master these and you will see the strength of spectacles at a glance!

Symbol: D / Base data: refractivity.
Unit that indicates the degree (refractivity) of spectacles lenses. Shows the reciprocal number of the planned focal length using meter as the unit.

Indicates the refractive index of lenses

When you look a bit closer at a pair of glasses, you will see figures such as “+0.5” and “+2.0”. These figures are called “diopters” and they represent the refractive index of a lens. This tells us at what distance light that passes through a lens focuses.