My mom was diagnosed with MS about 30 years ago. Her only symptom during those years has been pain behind one of her eyes. Like you, she has no vision loss, just the pain. In her case it usually happens about 2x per month and lasts 1 - 3 days. My assumption is that she has mylin damage on her optic nerve that just periodically flares up. It can be very painful for her, but she treats it with Ibuprophin and rest, which has been effective for her.