Groove on bottom of half-frame eye glasses - normal or not?

Question

I just got my first pair of half-frame glasses. I noticed that the bottom of the lens has a notch as though it was designed to fit into a full frame glasses. Is this normal? or did they just make do with the first set of lenses they got their hands on?

Answer 1

If you are talking about the channel grooved around the lens it is there on purpose and has a reason. If you look closely you will most probably see a monofilament line in the channel. This is there to hold your lens in. Something has to hold them in the frame.

Answer 2

It has to be there because there is a thin piece of fishing like line that is holding the frames up.  You have to be careful with half frames because you can pop the lenses out very easy.