I think Devic's generally just effects the eyes and the episodes are far more intense than just ON. It could be that you have both MS and Devic's. I also think that in many Devic's patients their MRIs are clear. I'll have to check with one of my friends as her dad has Devic's. I'll get back to you.
In the meantime, hang in there and I've been keeping you in my prayers.