Eye exercise can help reduce strained muscles and reduce eye fatigue. But if you can persist on doing them for a long time, you can achieve some result. If you have really very bad eyesight, you can turn to lasik eye surgery. lasik eye surgery can cure many vision problems. You can consult your eye doctor for more information. You can get perfect vision after this kind of surgery as long as you are a good candidate for it and there is nothing wrong within the recovery phase. Good luck!
I think eye exercise for eyesight improvement is a myth. Eye exercise can only help reduce eye strain while it can't improve eyesight. But they are good for eye health too. Besides, many ways such as herbal treatment and vitamins and nutrients can help maintain eye health other than improve eyesight too.
My nephew had tried some kinds of eye exercise for several months but he didn't get a good result in the end. The machines cost him thousands of Yuan. It is said that children' eyes are more flexible so it is possible to correct their vision problems, but I think the result may depend on which kind of vision problem the person has.