Astigmatism is a type of refractive error and is usually caused by an uneven cornea or unequal curvature. Regular astigmatism means that the refractive state is the same on the same meridian of the cornea, while irregular astigmatism means that the refractive state of the cornea is completely different on the same meridian or in different parts of the cornea. Irregular astigmatism is usually caused by various pathological factors, such as inflammation of the cornea, corneal scarring, cone corneas or pterygium after surgery, or lens dislocation, all of which may cause irregular astigmatism. For the correction of irregular astigmatism, corneal contact lenses and refractive surgery are currently the mainstay, and frame glasses are usually difficult to correct irregular astigmatism.