Myasthenia gravis preferentially affects young women or older men and commonly affects the extraocular muscles leading to eyelid drooping or double vision, but it might affect any skeletal muscle.
Myasthenia gravis can affect the extraocular muscles, which control movement of the eye as well as the eyelids, so individuals might have diplopia or double vision, as well as ptosis, or drooping eyelids.
Additionally, if there's damage to the nerves controlling eye movement, then eye movements can be painful and there can even be double vision, if the eyes can no longer move in a coordinated way.