check out this fellows review of three helmet type mounted mirrors, including Dengidog's Safe Zone and my Take-a-Look (which btw I mount onto the side plastic part of my helmet visor, not glasses--so its always there)

With all head mounted glasses, one has to shift focus a bit when looking into them, but I honestly dont find it hard to do, and although you are looking at something right in front of you, you actually are focusing at infinity more or less, as what you are looking at is far back. (to get a better idea of this, take a manual focus camera and hold a mirror so that you see something far away in it--put camera to eye and you will see that if you focus on the actual mirror, the glass and frame will be in focus, but the stuff 20 or 50 feet back will be out of focus-you have to focus the lens at 20 or 50 ft or whatever--its the same with your eyes looking into a small (or large) helmet mounted mirror--you are focusing your eyes at the distance the cars are actually behind you, not 4 inches in front of your eyes.

no matter which mirror like this one uses, our Dork-o-meters goes waaaaay up, but who gives a frack, I dont.