Astigmatism

Astigmatism is a vision condition that causes blurred vision at any distance due to the inability of the eye to focus clearly.  

Astigmatic corneas have irregular shape: Instead of uniform curvatures in all meridians, there is more curvature in one meridian than the others. The shape of the eyeball resembles more the shape of an American football rather then of soccer ball.

It can be inherited and is usually present from birth. Astigmatism can change as a child grows and it may improve or worsen over the years. It frequently occurs with myopia and hyperopia.