Bottom-heavy frame shapes like aviators, which are wider at the base than the top, help balance a heart face's narrow chin against its wider forehead.
The Styling Principle
Balance the forehead-to-chin taper by adding volume or width at the jawline and softening or minimizing width at the forehead and temples, which brings the upper and lower face into closer visual proportion. Bottom-heavy frame shapes like aviators, which are wider at the base than the top, help balance a heart face's narrow chin against its wider forehead.
Sizing
As with prescription frames, sunglasses width should roughly match your face's widest measurement — for a heart face that means sizing relative to cheekbones.