Unseen characters, eyeglasses, and buttered toast

Do these things mean something or not? If yes, then what?

So the eyeglasses are fairly obvious. Smiley gets an eye exam and a new pair of glasses just before being called in to investigate the mole. Watching his former colleagues with a fresh, clear set of eyes. Jim Prideaux says young Bill with glasses is a “good watcher”.

Buttered toast. In the first scene, the Hungarian legman sitting at the outdoor cafe is buttering some toast. Jim thinks they are waiting for a general to show, but it is a trap and an ambush. Later Oliver Lacon is buttering toast while Percy and Bland ask him to fund their London secret house.

There are several key characters seen only from the back - Ann Smiley, Karla, and Peter’s boyfriend. Why these 3?