Hello, I have RRMS and am a paraplegic because of it. I also have vision and balance issues. I was reaserching a trike before I lost the functions from the waist down. If you are only experiensing one sided weekness and ballence issues a trike is great choice. when you look at them there a few things to concider. One is foot placement. some trkes have the feet high and the body in a more laied down position. This will be less stable in the bike. Try and find one that the pedals are flat with the ride. this puts you in a more uprite position so you have less strain inorder to ballence. Second is steering. some have direct steering, where the grips are conested to the steering arm strait out in front of you. There require your arms to be raised for most of the riding and fatigue can come into play. the other type is steering below the seal. This allows your hands to be down at your sides and less fatige is an issue. caution though, watch what you ride over since all of your steering is below the frame. Last is check the gears. If you dont plan to ride long distances limit the number gears as you wont need them.
I am currently riding a quickie shark hand cycle that I am renting. Check with your local disable sports, they may have a few different kinds that you could try out before you take the plunge.