If you're looking for new glasses, Glasses USA has some of the best offers. There are discounts on both frames and lenses, so no matter what you're looking for, you're likely to find it there for less.

Buy one, get one free: With the code BOGOFREE you can get a second pair of glasses for free. The order can include one "premium" frame, and the discount will cover the cheaper of the two pairs of glasses. 

30% off frames: If you need only a single pair of glasses, use coupon code SAVE30 for 30% off and free shipping. This applies only to frames with basic prescription lenses, and it's not compatible with premium, on-sale or "new arrival" glasses. This coupon can be used to save on sunglasses as well. 

Other deals include 50% off lens upgrades with the code LENSES50, and you can save on select designer frames (though quite a few brands are excluded) with the promo code DESIGNER40. And finally, if you need glasses and contacts at the same time, when you spend over $120 on contacts, you can get a pair of glasses for free. Use offer code FREE-GLASSES. Just note that this offer isn't good on premium, luxury, sale, the Marsai Martin X GlassesUSA.com collection or the Von Miller x GlassesUSA.com collection.