Astigmatism changes

What is believed to be the cause of astigmatism? And, how is it possible for it to change on its' own? Mine improved over a year. What is the theory on the mechanism by which the cornea can alter its' shape? It seems amazing that the eye could change in that way.

[Michael J Kutryb, MD]

The shape of the cornea is mostly determined by genetic but over time the constant blinking of the eyelids can exert forces that are one other factor that can cause changes in the curvature of the cornea.  Changes in collagen that occur with age can also cause changes.  Hormaonal changes that occur at different times of like (pregnancy for example) can also cause significant changes in the cornea.  If you think about it almost all the parts of our bodies change over time so why would you not understand the cornea would also.