Find the best Sunglasses for Your Face Shape , The sunglass size should be in proportion with the face size. This means that smaller sunglasses are best for smaller faces; larger sunglasses for larger faces.
The frame shape should contrast with, that is, be the opposite of, the shape of the face.
These tips must not be taken as rules but they can help you to choose your right frame.

Heart-Shaped Face
A heart-shaped face like Hayden Panettiere's is characterized by a wide forehead, narrower jaw line, high cheekbones, and a narrow chin.
Sunnies that will suit you: Go for cat-eye shaped sunglasses—they will accentuate your face shape the best. Pick up a pair like these two.

Oval-Shaped Face
An oval-shaped face, It's characterized by balanced proportions, a narrow forehead and jaw line, a chin that is slightly narrower than the forehead, and typically high cheekbones.
Sunnies that will suit you: Any style, lucky you! Try on a pair like these two.

A Round-Shaped Face
It has an equal width and length, and is characterized by soft curves with few angles, if any.
Sunnies that will suit you: Those with rounder faces should go for angular frames, which help add definition. Opt for styles like these two.

A Square-Shaped Face
A square-shaped face, is usually proportional in length and width. It's characterized by a defined jaw, square chin, and a broad forehead.
Sunnies that will suit you: Try round glasses—they will highlight your best features. Try these two on for size