Causes of Astigmatism

Causes of astigmatism include -

Irregular shape of the cornea - Normally the cornea is smooth and equally curved in all directions. With astigmatism, the cornea is ‘warped’, meaning it curves more in one direction and objects appear somewhat indistinct and slanted. This irregular shape of the cornea prevents light from focusing properly on the retina. As a result, a person's vision may be blurred at all distances. Normally cornea is spherical. Astigmatism can also occur when the cornea's shape is more oblong than 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.

Pressure of the eyelids on the cornea.
Incorrect posture or an increased usage of the eyes for close work.
Heredity.
Rarely, astigmatism 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.