Hi and welcome,
Technically the presence of 2 or more IgG bands in the CSF, but not in the corresponding serum specimen, is considered positive, though some labs (eg Mayo) actually need 4 or more but the presence of oligoclonal bands is not specific to MS.
"Oligoclonal bands are found in a variety of inflammatory and infectious CNS disorders, including paraneoplastic disorders, CNS lupus, neurosarcoidosis, and Behçet’s disease; however, the majority of cases in which oligoclonal bands are seen are infectious. " https://www.sciencedirect.com/topics/medicine-and-dentistry/oligoclonal-band
You don't mention any current clinically abnormal neurological signs, MS suggestive symptoms etc etc that would today place neurological conditions like MS on your potential causes list so IF you are saying that almost 10 years after being dx with an isolated incident of ON, your brain and spinal MRI's are still normal but your obands have increased from 1 to 3 that is unique, i think you'll find that the likelyhood of you having a neurological condition like MS after this long a time frame without more specific suggestive-consistent diagnostic evidence is very low.
Hope that helps.....JJ