Whats the highest and the lowest diopter on a corrective lens.?

Question

I know that anyone with vision worse than 20/200 that cannot be improved with corrective lenses is considered legally blind.

But what is the highest and lowest corrective lens?

Answer 1

They start at a +/- 0.25 ( 1/4 D )...and in the minus powers can be made up to a - 30.00...