Just thought I'd add a link to a gallery of photos of endodontists training on their honking microscopes. I swear the objective lens was as big as a saucer. Of course it was about two inches above my mouth, and hence hovering next to my eye.
Dr. Lampert must consume no caffeine. He's chattering with his nurse about measurements in the 1-3 millimeter range and using his hands as guided by this humongous microscope, and not a twitch. If I had to do what he does, I'm afraid I'd only be able to do 'group' root canals.