Poorman is correct. There are rectus muscles around the eye as well.

Poorman, I have had some of the worst double vision my opto and neuro has ever seen. It is absolutely miserable. Mestinon didn't do much for me, and I'm also allergic to it, so I had to turn to other meds. Once you find "the one" you will appreciate every moment of clear vision. I hope it happens for you soon.