Astigmatism - In the normal eye, light enters through the cornea (the clear front surface of the eye) and comes to a focus on the retina in the back of the eye. Astigmatism occurs when the cornea is not spherical in shape (like a baseball) and instead is longer in one direction (like a football). This causes the light to focus in more than one place within the eye, causing your vision to be distorted or blurred. Astigmatism is often responsible for starbursts, "ghosting" images, and halos or rings around lights at night.
Astigmatism is usually corrected with glasses or contact lenses but it can also be corrected surgically with LASIK, PRK, or Limbal Relaxing Incisions.