Optical power

[1] High optical power corresponds to short focal length.

The SI unit for optical power is the inverse metre (m−1), which, in this case, is commonly called the dioptre (symbol: dpt or D).

When a lens is immersed in a refractive medium, its optical power and focal length change.

For two or more thin lenses close together, the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens: P = P1 + P2.

A myopic eye has too much power so light is focused in front of the retina.