Astigmatism is a condition caused by a misshaped cornea. Because the curve is uneven instead of a normal curve, the light rays bend improperly and are not refracted equally in all directions. As a result, one focus point on the retina is not achieved and distorted vision occurs. With Astigmatism, objects appear somewhat indistinct and distorted rather than sharp and clear.

Astigmatism can occur along with both nearsightedness and farsightedness. Like these conditions, it is usually hereditary and can be corrected with glasses, contacts, or surgery. In most cases, specially ground lenses are used to correct the path of the light ray as they enter the cornea.