Hey, hopefully I can be of help.
VR is a complicated platform to work with, as it can be very easy to become sick. I would be cautious with post processing directly on the eye, as this would cause a lot of sickness and cause people to go cross-eyed, as the lenses overlap.
This said, this is possible to do, although i would go the route of using a scene capture 2d and a render target placed a short distance in front of the camera… this would allow the user to recognize that it is a separate object. in the 2d scene capture, you can set up the post process to look like night vision.
Hope this was helpful, cheers.