I haven't heard about the eyesight or blurry vision due to the medication. However, I would contact your MS Neurologist Specialist in case he/she wants to see you that you may be exacerbating (not due to the medication, due to MS).
Check out my TOPIC on this website on timing of taking the medication and diet that has worked well for me and others. Obviously you can't do the aspirin or ibuprofen, but anything you take or medication you should work that out with your MS Neurologist Specialist.tecfidera-bg-12-dimethyl-fumarate-f52/topic22462.html
Perhaps some of the suggestions from several of us might help you minimize or eliminate some of the side effects.
has 24 hour nurse line you can look up the number there for any clinical questions.
Good Luck and Good Health to you.