Colin-
Check these out (bottom of the page) I used these glasses for nodic raceing and they work grear for high aerobic activity including biking and work really well in the cold snow and what not, they have interchangable lenses, good warrenty, and you can convert them from glasses into more hybrid gogle type while keeping low profile. Look on ebay for good deals. Just an idea...
http://www.rudyprojectusa.com/products/sunglasses/styles/ekynox.htm