Astigmatism causes a distortion or blurring of vision that is much like the "funny mirror" in an amusement park.

Astigmatism occurs when the cornea (clear front window of the eye) is shaped more like a football than a basketball. The misshapen cornea causes images to come into focus in different points in front of or behind the retina, instead of precisely on the retina.
 
  The Eye with Astigmatism
Glasses or contacts help to overcome the limitations of the misshapen cornea, allowing images to focus more precisely on the retina. This results in clearer vision. LASIK Laser Vision Correction changes the shape of the cornea itself, allowing images to focus more precisely on the retina, even without glasses or contacts.