Nobody wrote:
Is it possible to just solder the parts together? My mum's have
broken - the metal frame around one of the lenses split apart where it
joins the brow (?) i.e. the bit that sits on the nose. Glueing has
failed.

Take it to a decent optician, who will be able to braze or
silver solder it - if you get the metal too hot, it'll
collapse, but you need to get it hot as ordinary solder is
unlikely to be any good.