Hopefully if you have a pseudo tumor like the MRI suggests, that you'll be able to successfully treat it without having to resort to surgery and without too much damage to your vision.

If they do an LP, they're probably doing it to rule out MS or a pseudo tumor. Both MS and pseudo tumor are diagnosis' of exclusion...which means they have to exclude all the other diseases that can cause the symptoms before they can decide on the proper diagnosis.

Hopefully it's something benign that will go away on it's own without harming you.