I had IVIG and it helped me a lot with my double vision, during a flare from infection and antibiotics. My IVIG treatment was done as 4 hrs/day for 5 days and improved my symptoms by day two. My main MG symptom has always been double vision with a droopy eye lid, even though my neurologist tells me a have generalized MG, because I am anti body +. After having IVIG and more recently adding Cellcept, I have reduced my Prednisone gradually to .5 mg every two days and only 1 to 5 mg of mestinon occasionally when needed due to some temporary trigger. I am also on Mycophenolate Mofetil (Cellcept), which takes a very long time (up to 6 to 12 months) to be fully effective. My doctor attributes my ability to get by on such low doses of the other meds to be due to the Cellcept finally kicking in.
BTW, I find the liquid form of mestinon to cause fewer stomach issues.