JJ, There has been a bit of discussion on this topic but no real consensus. I'll describe what I think happens to me but I may not have it quite right for you. When my MG flares I can get DV which can go away by closing one eye. For me, the double images are side by side (which means one or both of my eyes are wandering in the left-right direction).

Sometimes I have a problem with DV and it won't go away by closing an eye. In this case, it is usually not so bad and the images are up and down. It also turns out I have astigmatism in both eyes in the up-down direction. I think what happens is that my eyes get tired, have trouble focusing, and make the astigmatism more noticeable. It may even be that my eyelid gets tired, droops a bit and changes the way my eye lens sees.

If I'm right about this, my double eye DV is just 'normal' MG DV. My single eye DV is because I have astigmatism and my eyes can't focus well because they are tired. I talked to my neuro about this and was told the focusing muscles in your eyes aren't affected by MG because they are not voluntary muscles. Many people on this forum would disagree with this statement and I am one of them.

To see if this explanation holds water in your case, you might want to pay attention to lighting conditions when you sense some single eye DV. In bright light, eye defects like astigmatism won't occur because your pupils shrink and diminish the defect. In dim light, the single eye DV gets worse because your pupils open to let more light in.

I don't know if this helps. A few people here have this issue. It's not clear anyone can explain it. I have much more trouble focusing since MG appeared. My neuro can't explain it except to recommend new glasses. I have an explanation but I don't know if it is right.