You misunderstand how mirrors work. You're not looking at the mirror, you're looking at stuff THOUGH the mirror.

If you are looking at something 20 feet behind you in a mirror 2 inches from your head, your eye needs to focus at a point 20 feet, 2 inches away.

My favorite is the Cycleaware Reflex. I used to use a Take-A-Look, but I had an accident and wound up having the mirror's stiff wire and sharp-ish edge of the mirror ground into my face, requiring 18 stitches to close. The Cycleaware does not have sharp edges or stiff wire to ram into your face or eye.