I used these guys a while ago and thought I might share this with everyone here.
I purchased a pair of prescription sunglasses with Drivewear lenses in them and got them delivered for $113, I was quoted $580 just for the lenses locally.
They are really great quality, perfect prescription. All you need to do is grab your prescription from your optometrist and fill it out on the site when you order. Takes around a week for the glasses to be made and another 2 weeks for the Glasses to turn up.
The code I have included will give you 20% off your order.
It's always tricky to order a frame that you haven't tried on. I gather from their website that they also offer lens replacement on existing frames. It's unclear if the 20% offer applies though. But it looks like the 15% offer via code Y2013 may well do.