I have generalized myasthenia, but it is mostly contolled; one of the first symptoms to go/reappear is the double vision. Mestinon does not work very well on eyes; I would say that Prednisone has a much better impact on eyes; it has both long term effect, but also a short term improvement; by short term I mean after taking Prednisone (15 – 20 mg in my case), there is a notable improvement in double vision after about 5-6 hours which lasts for about another 8 hours.