Tighten the mirror bolts, or pop the bolts out and put rubber washers between the mirror and bracket surfaces. Oughta do it
I have found after 30 years; My eyes now flutter at the same rhythm as the mirrors vibrate. I can see perfect when backing.
Old thread, same old problem. @Ruthless is right. I can generally manage with the drivers side but with the passenger's side I've had to jump out and loosen the nut holding the 6 inch round mirror. Works like a charm. . Oh, don't forget to tighten it back up lol.