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Well, there is not much more to it than what you citation already says: It deflects your field of vision upwards, i.e. you can keep your head level, look into the glasses and you will see upwards. ...
Answer
Well, there is not much more to it than what you citation already says: It deflects your field of vision upwards, i.e. you can keep your head level, look into the glasses and you will see upwards. ...