I will give you a very basic understanding of how the eyes work. Light goes through the cornea, and behind the cornea is the lens that focuses on how we see. We call the muscle responsible for flexing and shaping the lens
We also have extraocular muscles that control the movement of the eyeball itself. These movements are up, down, left, right,
Astigmatism is a condition that causes blurred and double vision. It occurs when the cornea (the clear front cover of the eye) is irregularly shaped or sometimes because of the curvature of the lens inside the eye.
The ciliary muscle is the key to how the lens focuses but the internal muscle has to work with the extra-ocular muscles for everything to work properly together. Relaxation is the key for the whole eye system to work properly.