Whoa.
I wore my glasses to work today, which is a pretty rare occurrence, and noted that my new prescription is exceptionally strong. Such that, if I turn my head just right, and look out of the very edge of my left lens, I see a yellow and a red-orange band at the leading edge of objects, and an aqua and a purple band at the trailing edge. That lens is at a -11 diopter; I've heard that -10 is legally blind.