Astigmatism can also occur when the cornea's shape is more oblong than spherical. Normally cornea is spherical. The oblong shape causes light rays to focus

on two points at the back of your eye, rather than on just one. Many people are born with this oblong cornea, and the vision problem may get noticed over time. In some people, astigmatism may be due to pressure of the eyelids on the cornea. It can also be due to incorrect posture or an increased usage of the eyes for close work. Heredity is also a cause of astigmatism. Rarely it is caused by lid swellings in a condition called chalazia or due to corneal scars. An eye injury may cause the cornea to scar, changing the path of light as it enters the eye. It may also be due to keratoconus, a rare condition in which the cornea loses its normal shape. Some patients experience surgically induced astigmatism after eye surgery. Sutures that are tightly placed can cause a slight wrinkling of the cornea and the patient will experience astigmatism until the surgical wound is healed.