Thoroughly enjoyed Eric Wilson's article for yesterday's New York Times, on why this year's cool sunglasses shape is round.
The piece does exactly what I wish more fashion articles would: examine a style outbreak as an art historian would examine an old master: seriously. Since it's the Times, the piece mentions at the obvious influence (John Lennon) but then digs comprehensively past it, citing art exhibitions, current theatre, and presenting the opinions of sources involved in their creation, marketing, and sale--in other words, the people who are putting round lenses square on the faces of the world's hippest buyers.
While it wasn't mentioned by those in the creative arena I wonder if there might be one influence more: steampunk.
For me this counts as the most exciting and original style movement in recent years. For those who haven't come across it, consider it Goth's nerdy younger sibling--a style amalgam of Victorian layered blacks and the mechanical contraptions of the same period. Brass gearing and rubber tubing and leather strapwork hold these looks together, just as they kept the engines clacking back at the turn of the century.
One of the signature looks of Steampunk is round brass goggles and glasses. I think they look incredibly cool. But brass isn't for everybody, which is why most of the rest of us will opt for tortoiseshell.