In astigmatism, the eye is oval like a football, and not spherical. The image is formed at two different points inside the eye. This means that images of different orientations are focused at different parts of the eye and that the image on the retina is blurred.
Many patients have astigmatism combined with myopia or hyperopia. The computer of the High Definition Custom Laser (Schwind Amaris or Zeiss MEL-80) permits the correction of both defects during the same treatment session.