We've all seen Mary-Kate Olsen parading around in her retro round sunnies.  Unlike gigantically oversized 'it girl' frames or wayfarers, this sunny day trend took its time leaping from celebs to street fashionistas.  But with these mod round frames showing up on Spring/Summer 2009 runways like Ralph Lauren, and with versions now available in stores like F21, expect to see this style ringing in the new year.

Above:  Mary-Kate Olsen in retro frames; Lily Allen keeps it classic, pairing mod sunglasses with a black pea coat.

In general, round sunglasses are good to break up a long face, but these I think are best on anyone with a lot of confidence and don't-care-what-anyone-thinks attitude.  I suggest skipping M-K's look above (seriously, sometimes I think she just gets bored and tries her hardest to look ugly) and aiming for a chic basic look, making your sunnies your boldest accessory.

The most wearable version of these I've found are these black round Annie Glasses (above) from Nasty Gal Vintage, $40.  You can also snag a pair of round sunnies in white from Forever 21 for under $6.

Although round frames really don't work on my round face, I am a sucker when it comes to trends and could definitely see myself donning these in the next few months.  In fact, the more I look at these the less strange they seem.  What are your thoughts?

Sources: Fashion-stylist.net, Style.com