It may be useful for you who are with myopia through pranayama. However you could also do the eye exercise to cure the myopia. If your prescription is too high, you will have to do the surgery to get recovery of the eyes. You could just have a try on this on the precondition that you have the good rest of the eyes.
I have to say that pranayam can do a help to myopia. First, you should know that there are many people who are doing pranayam. And by doing it, it can be very beneficial for your body health. For example, by using pranayam, your body can become strong, flexible, sturdy and healthy. Also, there are some evidences which show that pranayama benefits in reducing high blood pressure, fatigue, and mental stress. And we can say that in that way, it will also be beneficial to eyes, being good for myopia. But you also need know that it cannot cure myopia.
Myopia is not easy to be healed but be controlled. Pranayama can correct and control myopia indeed so that blindness and some other vision problems will not accompany myopia. When you are old, your vision can much better than the same aging people by pranayama.