To understand astigmatism we need to know that our eyes are focused by the cornea, the clear watch glass outer window of the eye, and the lens, which is just behind the iris or colored part of the eye. If one or both of these surfaces are not perfectly round, astigmatism is present. Compare an egg to a ping-pong ball, or a football to a basketball. The egg and football have a lot of astigmatism, which the ping-pong ball and basketball have none.
Astigmatism may cause blurred vision, eyestrain or headache. Small amounts of astigmatism may be ignored. However, if you are having symptoms, glasses or contact lenses may help you.