Have both of you been checked for brain tumors/growths and if none found with a general brain scan, have they made sure both of you don't have a pituitary tumor, which often cannot be seen on the general scan, and therefore, one should have a dynamic pituitary MRI to look for? When pituitary or pituitary/hypothalamic tumors press on the optic nerve they can cause visual problems.
I have had similar situations and still do. I was diagnosed with Vertigo (cause unknown) a few years back and the ENT continues to say that is most likely the cause. Recently I have also been diagnosed with low blood pressure because my blood pressure is normal then all of a sudden drops really fast and I pass out. I was told that this condition could be a cause for my vertigo as well. I also have began to go blind in my left eye but the cause is unknown. I was told that with my symptoms the best place to start is with a neurologist and with MS that would be the right path for you to take. They can determine if you are at risk for MS or have already developed it.