I had improvement of my vision and the droopy eyelids after 5 or 6 months of treatment with Mestinon. I also had to get the perfect dosage figured out, it was after a decrease in the dosage that the double vision went away (or at least the worst of it). Too much Mestinon for me causes double vision.

Maybe you need more time on the treatment, or talk with your doctor about adjustments to the dosages.