The majority of astigmatism in children is caused by congenital factors, that is, genetic factors. If one or both parents of the child have astigmatism, the probability of the child having astigmatism is higher than that of other children.

There are also a few cases where a child's astigmatism is caused by acquired factors, such as surgery, trauma, or illness, all of which may cause changes in the curvature of the cornea and lens. Additionally, a lack of outdoor activities and poor eye habits might also promote the development of astigmatism.

It is recommended that once a child is diagnosed with astigmatism, they should go to a reputable hospital for examination and then get appropriate treatment to improve the condition, otherwise, it could impact their vision.