LOD & FOV for SteamVR CameraRig

I am trying to implement Field of View and Level Of Detail for Steam VR's CameraRig, i am using HTC Vive with Unity 5.5.0f3 Personal Edition, i have tried to implement it with a slider monement, i am able to see the values changing on slider but camera isn't changing.

Any Suggestion.

Regards,
JungLee.