blurred vision can be caused by:

1. imbalanced (let's say in the case of MG- tired) extraocular muscles.
2. affected intraocular muscle (it's called cilliary muscle). this involvement is more rare but accomodation deficits in MG have been reported
3. rather constant blur or smearing due to cataracts
4. refraction error and ton of other binocular vision anomalies or ophthalmologic conditions not linked to MG
...

therefore for the sake of simplicity- Blurry vision" in MG is usually is indeed slight double vision.

Best;
Tom