Does anyone recognize this movie?

I saw it as a little kid, and it was a very special day for me. I really want to watch it again, but the only thing I can remember is that the villain had a microscope like thing with two lenses. He would ask a person to look at what was under the lenses, and when they tried they wouldn't see anything. The villain would then tell them to adjust the microscope thing using a knob connected to it, only, the moment the person twisted the knob, two blades would come out of each scope and blind the person. Please, please tell me if you know this movie, I know it was in theatres and everything at one point.