Is there anyway to reduce lens distortion on Gear VR?

I have been following this tutorial :

https://developer.vuforia.com/library/articles/Solution/Integrating-Gear-VR-and-the-AR-VR-Sample-in-Unity-5-3-and-above

Using Unity 5.3.3 32bit and vuforia-samples-eyewear-unity-5-5-9.zip.

I've test with Gear VR and every thing looks good, except there's a lot of lens distortion around  the edge.

Is there anyway to fix this distortion?