Specifically what does Rx, 0+/- mean?
Oakley sells prescription lenses. They will make them for ANY X-Metal. Many O stores even have an optometrist in-store part time where you can get an eye exam and they can send your order directly in to Oakley to have the lenses made. Otherwise, an optometrist or ophthalmologist would assess your vision, consult, and write your prescription. The thing is you may or may not require significant correction, requiring a very weak|minimal prescription/Rx, if any. This is what I am trying to convey with the 0+/- ... you could get a minimal Rx, maybe a +.5 or even that 0.0, though most people can use some correction. The big downside is cost. There are other factors as well. For example, it is possible for a very high|strong Rx to require a specific curvature that does not suit all frames.
Hope this helps