Welcome back, Freesia38!

ON almost always involves vision problems but those may include diminished color vision or blurred vision--problems you might not have been keenly aware of.

About your other question, MS can do just about anything, or at least it often seems that way.

Are you sure that the optometrist recommended an MRI for diagnosing optic neuritis? I haven't heard of that. Usually a neurologist or an ophthalmologist can see the optic nerve but it does take some skill and training, and maybe the optometrist meant that you need to consult one of those types of doctors.

I believe that the visual evoked potentials test can be useful in diagnosing ON but the easier way is by getting a look at the optic nerve, which is the only nerve in the body that can be seen.

When I was diagnosed with MS, the neurologist had trouble seeing my optic nerve and had to call in another doctor. Together they got it right, and concluded that because I have severe myopia, the optic nerve was particularly hard to see, but they did find it.