When I was very young, my vision started getting a bit blurry. I went to an eye doctor who examined me and found that I had a slight astigmatism in one eye. The other eye was perfect. He went on to say that my right eye, which had the defect, was defaulting to the left eye and letting it do all the work so to speak. He said, "I can give you a prescription for eye glasses, but I think it would be better for you in the long run if we first try strengthening your right eye. He suggested that I wear an eye patch over my left (good) eye for several hours a day and let the right eye do all the work of focusing.
Sure enough, my vision improved very rapidly as my right eye stopped slacking off and its focusing muscles got stronger.
This may not work for everyone, but I thought it was worth sharing, just in case.