Astigmatism is due to the irregular cornea curvature, also known as the refractive error. This disorder often refers to the irregular shaped cornea. Theoretically, the eye's cornea should be perfectly round. But if the cornea is oval, the cornea will not correctly focus on the retina.

Astigmatism normally has the following two types: corneal astigmatism, lenticular astigmatism. Corneal astigmatism is caused by irregularly shaped cornea. Lenticular astigmatism is caused by irregularly shaped eye lens.

Astigmatism Symptoms often include: blurred vision, distorted vision, eye strain, headache or fatigue. Usually astigmatism is hereditary. But eye injuries may also lead to astigmatism. Corrective eyewear or refractive surgery can be used to correct astigmatism.