Thank you very much for you help and support
The best thing to do, if you feel that your original doctor didn't do enough, is perhaps to find a new doctor.
The glaucoma isn't related to a neurological disease that I can think of. The vitamin D needs to be dealt with. You can start doing this on your own. 2,000 units (iu's) daily, of the form D3. That's the most bio-available form. The optic nerve damage seems like enough to warrant another MRI, but Optic Neuritis doesn't usually image well on an MRI.
If there are detectable lesions on your brain, the doctor will decide which route to take next. (Sometimes they are simply too small to detect.) Ask for MRI with contrast (for the brain), and that they rule out MS. Advocate for yourself. Whether your physician likes it or not, you have a right to ask him to check on the things you're concerned about. If your brain MRI still shows nothing, ask for one of your spine- being specific that it be to rule out MS lesions. (Spinal MRI's are not always performed with contrast.)
If there truly are no lesions at all, however tiny- MS is unlikely. But there are other things that are known to cause neurological symptoms: Thyroid disease, B vitamin deficiencies, certain types of Migraine, and even severe stress!
Optic nerve damage does occur in the general population from time to time. So, even if the MRI shows lesions, your doctor may elect to wait and see. This is a hard disease to diagnose- and hard to rule out too.
Good luck! I hope you get the answers you need.