Astigmatism is partly caused by congenital development of the eye, during the development of the eyeball by various factors, the eyeball is not in a spherical state, so the refractive error of each diameter is different, which will produce astigmatism, and most of the astigmatism is from corneal astigmatism. Most congenital astigmatism is regular and can be corrected with eyeglasses, while acquired astigmatism, which is related to refractive error, eye trauma, eye surgery, or corneal scarring after corneal disease, may be irregular. In severe cases of irregular astigmatism, some patients may not be able to be corrected with framed glasses and need to be corrected with rigid corneal contact lenses.