Style and fashion go in cycles. This is true for sunglasses as well as clothing. As a matter of fact oversized vintage sunglasses are back in style.
Finally, we are through with the little bug eyed purple sunglasses with tiny wire frames that did little to protect your eyes. We are getting back to something big so that your eyes are protected from those sun rays.
If you are having trouble visualizing these oversized sunglasses, think of Elvis Presley. Elvis wore the sunglasses that were popular during the late 70s and early 80s. His favorite style seems to have been the aviator shape glasses. Aviator glasses are in the shape of a right triangle with the corners well rounded. The glasses are wider at the outer edge of the face and narrower toward the nose. The lenses are basically a straight line across the top. You can also get vintage eyeglasses at http://www.classicspecs.com/.
Another popular style had rectangular lenses. These glasses were often curved to fit around the face, but the basic shape was that of a rectangle. Of course, once again corners of the rectangle were rounded off. Another variation of the rectangle was the square glasses.
When looking for oversized vintage sunglasses, you will find that there are new sunglass style that have been set aside for years that have been brought back out for sale. Additionally you will find many replicas of the oversized vintage sunglasses as well as new designs that may have never actually surfaced during the vintage years.