Originally Posted by
Leisesturm
I can see no scientific reason why they couldn't. If its a MIRROR you can use it to see behind you. Period. Just because a helmet or eyeglass mirror is close to your face does NOT confer magical powers to outperform handlebar mirrors. If you were right then cars, trucks, and buses would have some kind of driver enhancement, rather than mounting mirrors to fixed points on the vehicle.
But a mirror mounted on your helmet or glasses can be used to scan across a wider area behind you. You just have to turn your head a bit. If you did that with a bar-mounted mirror, you'd be swerving around the lane.