Thanks for all the replies.
I am looking at the bates method for eyesight improvement as well, but I am not imagining black. It is just the darkness from closing the eyes. Maybe I need to have this type of imagination for any further improvements in my eye.
When you say elephant, some people might be able to see an elephant in there heads, but honestly I see nothing. Its not that I don't think it worth it, in fact I feel handicapped not having this type of ability.
I can talk in my head, but that is as far as it goes. Anyone know what this type of problem might be. Or any types of courses and books I can look up?