When I wear any type of glasses either sunglasses or a friends prescription pair as a joke or anything... the corners of my mouth itch uncontrollably and I find it unbearable, the only way to stop them itching is to remove said pair of glasses. Even I think this is wierd so don't hold back :)

I can't think of any way that your eyes or vision are linked to your oral muscles, so it is definitely odd. Perhaps the glasses rest on a muscle causing a spasm, which you identify as an itch?