I don't know a whole lot about this illness, but I do know the things that some people with this condition experience imaginary things just as we do real things.
However, I do know that some people are gifted and that they do see things that others don't and those things are real as well: spiritual things that are invisible to most people, but nevertheless actually there to people who have been given this gift. I'm very skeptical about this, even though I believe in a spiritual word, and I know a person who actually does see things: I know she's not a liar.
It is really hard to know where medicine stops and where faith and the supernatural begin.