This has been asked before, but what is the degree of precision in placing the reflectors in the lenses? If I was to hand over the glasses to someone else for a test, how much of a difference in our physiognomy would it take to render the glasses useless?
And how do you handle the differences in peoples physiognomy, particularly the bridge of their noses, when creating the individual glasses? Some people have wide noses, some have flat noses, etc. And there's also the matter of habit; some people like to wear their glasses high on their nose, while others tend to wear them lower... If the tolerance is minimal, how do you handle these variables?