I just bought the eyeglasses from Walmart with the medicaid. About the sams club, you can call their sale department and ask the detail about the paying methods. About the telephone number, you can search online which will give you the satisfied answer. Usually the stores may provide the opportunity of paying by vsp insurance.
I heard that sams club is as good as Costco to buy eyeglasses. But they are out of network for VSP insurance. Nevertheless, their eyeglasses dramatically less expensive and they work directly with the insurer to take the amount covered for out-of-network providers. So, they still help you save money and also save your time on waiting for reimbursement. Good luck.