"Vision loss is probably one of the most disabling things that happens to people with MS," said lead researcher Dr. Laura J. Balcer, an associate professor of neurology at the University of Pennsylvania School of Medicine. "The exciting thing is, first, that we now have an eye-chart test that can pick that up and can show if treatments help vision. Second, this particular drug appears to help prevent vision loss."
I haven't had much noticeable vision trouble, though I remember several years ago I had a bit of vision loss in my right eye when I got overheated. Seems like it mostly resolved after a month or so.