Astigmatism is a defect eye characterized by different corneal refraction between two meridians, thus preventing the clear focus of objects. The cornea is the transparent region that is in the anterior portion of the eye and acts as a lens through which light passes that is focused onto the retina at the back of the eye. The surface of the cornea must be symmetrical and regular in their curvatures, otherwise astigmatism occurs.
In the human eye astigmatism is very common in varying degrees and is often associated with other refractive errors such as nearsightedness or farsightedness.
Can be corrected by using cylindrical lenses, contact lenses or refractive surgery (LASIK).