"ON" is shorthand for "Optic Neuritis". MS can cause vision problems.

If you're able to do physical therapy and exercise, you should try to do it. I need to exercise a lot more often than I used to. I'm pretty sure some of my fatigue is from the MS, but I also sit around at my computer all the time reading. When you sit at a computer all day, your body tends to lean forward in positions that are not really good for your posture.

Plus, sitting all day can actually make a person weaker. You need to use your muscles and strength every day or you lose it eventually. I need to get better at getting up out of my computer chair and moving around.