I find Avonex to be extremely well tolerated and effective in controlling both relapses as well as playing a role in retarding the progression of disability over time. If this medicine is helping to arrest further attacks of optic neuritis, and you are tolerating it with reasonable or no side effects, I would continue this therapy for now. I do not have optic neuritis and I have not heard from my doctor. I think it is becoming less of a problem or I am just getting used to it. Problems with extraocular movements causing double vision are uncommon, but not rare in MS, and generally transient.
Optic neuritis implies a separate site of involvement in the optic nerve.
It sounds like there are multiple lesions in space, perhaps also in time. These would constitute genuine relapses. I am a 19 year old woman and I was diagnosed with MS before the age of sixteen. I am very curious to know if a diagnosis at this age is uncommon. Unfortunately, I never had anyone to relate to when I was diagnosed.