Rx is prescription.
Keep in mind that the safety advantages you speak of are the material and not the brand.
Oakleys are cool
and I also like them. What you like about the Oakleys is the styling and not the safety which can be purchased otherwise. Besides the "cool" styling the lenses are optically correct. If you want a pair of Rx Oakleys, including all three lenses, you will pay a pretty $$$$ for them. If it is worth it to you by all means get them, otherwise realise there are more inexpensive glasses available. If I had the money I'd buy an M3 BMW.