Here are the steps on how to use Promo Codes when shopping at diffeyewear.com: Add your favorite items to the shopping cart, then click to log in or create a new account, then go back to the shopping cart interface of diffeyewear.com and select the items you want to buy. Then, select the corresponding Promo Codes to complete the payment. It should be noted that different DIFF Eyewear Coupons have corresponding usage conditions. Also, welcome to a very popular recent promotion: Shop Prescription Glasses Coupon.