This maybe a stupid question, but how do I know if the nose bridge is loose or tight? Are we talking the movement of the lens up and down the glasses? Or back and forth causing looseness and the glasses to fall off the face. Reason I am asking because I am selling a pair of glasses and I am being asked about the nose bride and arms of the glasses. They feel snug on my face, which is pretty small to begin with and don't have an issue with back and forth movement. Thank you.