Astigmatism is a refractive error that occurs when the curvature of the cornea or lens is abnormal. In an ideal world, the eye ought to have the shape of a soccer ball (a sphere). This shape will allow light to be focused to a point, which leads to visualizing a clear image. If the eye is shaped more like a football, as is the case when corneal astigmatism is present, then light that enters the eye will not be focused to a point. This leads to a blurred image in the eye. In children, astigmatism is usually corrected with the use of glasses or contact lenses when there is a large amount of it or when there is an asymmetric amount between the two eyes. If astigmatism is not corrected in these scenarios, then there is a risk of amblyopia (lazy eye) developing.