I believe John Carmack has discussed this idea in regard to VR. I haven't actually tried current VR or tracked the development that closely to say whether this

I believe John Carmack has discussed this idea in regard to VR. I haven't actually tried current VR or tracked the development that closely to say whether this is currently feasible or not, but VR with eye tracking is perfect place for optimization. Why have high res textures and such pushed out to what you are not looking at.