What is high index and how do I know if I need it?

A high index lens is a lens that has a higher index of refraction. Meaning it has a greater ability to bend light to provide a clear vision for people with stronger prescription glasses while keeping the lens thin and light.

You will likely need high index lenses if you fall into the following total power ranges.

Sunglasses: +3 to -6

Eyeglasses (Clear): -2 to -7