I'm just this thread, and the B12 issue is one I have. With the optic neuritis, I lost a lot of color and contrast sense ( lost even before the ON, but is related). No eye dr could give me an explanation.
Then After surgery, due to the anesthesia, lost all color--took many weeks to get it somewhat normal, used B12 shots, Zn and B6.
Again, years later, endoscopy--gastric atrophy-BUT acc to Dr, not in area where B12 absorbed.
Then, throwing all Dr info to the wind, got my osteopath to let me give myself B12 shots daily--after 1 month, could see things have never seen in my life, including colors and depth etc. (I now use injectible Methyllcobalamin form)
AND more energy (a major problem with me is total exhaustion no matter what).
My B12 levels are over 2000 (they don't record above that).
But super dosing on B12 is one of major helps for me. Also think clearer, better skin tone.