Mirror coating is purely cosmetic and are available in an assortment of colors and the wearer perceives no difference in vision regardless of what color the coating is.
Mirror coatings are generally applied to sunglass tinted lenses. Obviously, a highly reflective coating prevents others from seeing the eyes of the wearer.
A mirror coating is also called reflective coating which is a thin film of highly reflective material spread over the glasses surface. It is
used to reduce the reflects rays from surfaces, such as water, snow and ice.