You may also ask for a cervical and thoracic spine Mri. I had just brain and it was questionable, not definitive for ms, essentially normal few spots that could be from migraine, bump or hitting head (like a car accident, slip on ice or fall off horse, even normal aging).... but some months later when cervical and thoracic was done, pretty clear where ms had set up house.
I also have had eye episodes but testing showed optic nerve fat and healthy, literally neuro ophthalmologist description.
Consider a ms experienced doctor to help you get answers, Ms or otherwise. My first neuro was hell bent it was CNS lyme, he refused to take off the blinders.
Good luck and keep posting!
I do know that you can have optic neuritis with things other than MS.
It can go away, like when you had your MRI. I have had it, and could only see orange and green at traffic lights, which my eye doctor said was ON. My ON never showed up on my MRIs and went away.
You may need to find another neurologist who specializes in MS. I went thru 3-4 before I found the wonderful one I have now, who took the same MRI that radiologist and neuros said showed nothing and showed me all of the lesions. Make sure you keep a copy of the MRIs; as the lesions attempt to heal themselves and become invisible sometimes.
It takes years sometimes. I found my wonderful neuro in 2011 but he says I've probably had MS since 1981. Go figure. There are also many tests and other diseases that mimic MS that have to be ruled out. So take a deep breath and find an MS specialist.