Cheers Jen, that makes sense.
I'll try and be clear about why I asked the original question.
Expected behaviour; With VR enabled, given a simple a scene when I tilt my head in different axis I expect to see the scene shift accordingly.
Observed behaviour: Scene elements like a skybox and terrain appear to parallax against foreground objects causing nausea. Mostly when looking up and down. I initially put this down to improper distortion. It's not something I've experienced when replicating the scene in another engine.
What I tried: After adding trees to the scene, the observed height of a tree (apparent image height as seen within the headset) appears to change when looking up and down.
Thoughts/suggestions?