Astigmatism is a condition in which objects, both near and distant, appear blurred. The cornea and lens of the eye are normally spherical. When one or both are curved more steeply in one meridian than another, the optics take on a toric shape (like a football). Most commonly, astigmatism is caused by a cornea that is more curved in the vertical meridian than in the horizontal meridian, like a football resting on the ground. This uneven curvature prevents light rays entering the eye from focusing to a single point on the retina, blurring the vision. Astigmatism often occurs in combination with myopia and hyperopia.

Astigmatism can be treated with LASIK, PRK/LASEK and AK.