Picture of Astigmatism
Astigmatism is a common form of visual impairment in which an image is blurred due to an irregularity in the curvature of the front surface of the eye, the cornea. In astigmatism, the curve of the cornea is shaped more like an American football or a rugby ball rather than a normal spherical basketball. Astigmatism occurs in nearly everybody to some degree. Astigmatism can be hereditary and is often present at birth. It can also result from pressure from the eyelids on the cornea. Almost all degrees of astigmatism can be corrected with properly prescribed eyeglasses or contact lenses. For a person with only a slight degree of astigmatism, corrective lenses may not be needed at all, as long as other conditions such as nearsightedness or farsightedness are not present. Another method for correcting astigmatism is by changing the shape of the cornea through refractive laser eye surgery.
Image Source: Dr. Andrew A. Dahl, M.D., F.A.C.S.
Text: MedicineNet - Astigmatism and Your Eyes