To elongate your face and make it look slimmer, opt for narrow angular deep frames with a bridge to widen the eyes. Rectangular frames are the best pick.
The oval face
People with oval faces should opt for wider sunglasses; the sunglasses' frame is supposed to be broader than the broadest feature on your face. You can also opt for a shallow, not too narrow frame.
The square face
In order to make it look long, you should lean towards rounded frames to balance out all your angles.
The heart face
For this type of face, glasses should always provide a nice contrast to your face shape to create a sense of balance and highlight natural features.