I never saw a revi "in action", but I read somewhere
that you can get only a clear image of the pipper on a straight line behind the revi .
If you are a little bit aside the optimal line you won't see a thing.
This means you cannot use a gunsight with both eyes the same time.
Just as Animal said, you aim with one eye.
I am not sure, but there was a good explanation here in the UBB some time ago.