The good news is that they clearly appear to have excluded "masses"--which i think is doctor speak for "no brain tumors found". This is very very good.
MS appears to be in consideration, but before you totally freak out, you need to know this:
1. My friend had exactly what you had (optic nerve inflammation is a few leasons on MRI with contrast). I thought for sure that meant MS, but he got a referral to a neurologist who basically told him they don't diagnose MS until the second episode, and in the majority of patients there is just one episode and it stops there, so they never do get diagnosed with MS--they just have an "ms-like" episode. My friend has not had any episodes since in 3 years, resolved to get stress under control (it's been implicated in the onset of MS), and at his neurologist's advice got on high dosage of vitamin D is there is evidence that is can prevent MS.
2. His vision symptoms resolved when the inflammation was brought under control. I googled and see that you may get on a steorid treatment or something similar to get inflammation under control, and I think it is expected to essentially resolve vision symtpoms.
3. Even if it is MS (although again, i am not sure they can even diagnose it after 1 episode), in the vast majoirty of patients it does not progress to anything serious, and they have great medications that keep it its tracks. It's not the disabling disease it once was.
The key thing is to keep your stress under control, get Vitamin D, and remind yourself--everyone will have "something" sooner or later, we all need to learn to cope with what life brings us. We are lucky to live in a time when there are so many effective treatments (and cursed to live in a time when we have more information from MRIs and medical dests than we know what to do with or what it even means sometimes).
Hang in there!