Hi and since we have met before, welcome!
I do not know much about eye issues and different eye conditions. I am assuming that the specialist was an ophthalmologist? Or even better a neuro-ophthalmologist? In my opinion, I think I would agree with the specialist about the recent ON. As for the remaining diagnoses I would get another ophthalmologist opinion.
I know this is difficult. Losing my eyesight is my biggest fear as well so I understand your panic but you need to gather all your information into a folder in chronological order and seek the opinion of a neuro-ophthalmologist. I just went to one for a 2nd opinion and he was wonderful and he cleared up a lot of issues for me.
Hang in there and spend some time compiling your information and write a time-line of what MS events occurred when. We have a Health Page written about this subject as well as many more subjects. The pages are in the upper right hand corner of the page next to the yellow icon. The link for the time-line is:
http://www.medhelp.org/health_pages/Multiple-Sclerosis/The-Importance-of-the-Timeline/show/765?cid=36
I hope some of what I shared helped. We have a member , michelleric, who knows about eye issues and works in the field. Perhaps you send her a note and you could ask her to read your post and see if she can help.
Keep us updated with how things are going.
Ren