I think it is possible to have optic neuritis from vitamin B12 deficiency. We can't produce vitamin B12 by ourselves, so we need to absorb it from other resources. Generally speaking, the main function of vitamin B12 is to create marrow red cells. Vitamin B12 deficiency would lead to malignant anemia and possible damages to neuro. It the an indispensable vitamin to the health of nervous system. So I think it is possible to have optic neuritis from deficiency of vitamin B12, after all it is one kind of neuritis. However, actually vitamin B1 deficiency is the most important trigger of optic neuritis. It is very common to use vitamin B1 and B12 as treatment of optic neuritis. Patients with optic neuritis should have a light diet with enough nutrition and more fresh vegetables and fruits. Avoid smoking, alcohol or pungent food. Keeping a happy and optimistical mood is important.
Optic neuritis is the inflammation of the optic nerve that may cause a complete or partial loss of vision. The optic nerve comprises axons that emerge from the retina of the eye and carry visual information to the primary visual nuclei, most of which is relayed to the occipital cortex of the brain to be processed into vision. Vitamin B12 deficiency is a low blood level of vitamin B12, which can cause permanent damage to nervous tissue if left untreated long enough and it also can cause optic neuritis.