People often say that when light and shadow are right, the brain fills in the rest. Behind the sunglasses, dark strokes and lighter patches suggest half-squinted eyes. The sun is apparently bright.
On the lower left side of the glasses there is no clear boundary between face and reddish-brown hair, yet we still read a stylized face. Subtle nuances on the forehead, together with the squinted eyes, create a slightly troubled expression.
But maybe you see something completely different. That is possible, because a painting itself does nothing (although it can do something WITH you); the viewer interprets the scene.
Wonderful how eyes and brains work... Painted after a work by Michael Carson.