In an astigmatic eye, the cornea has an uneven curvature. Instead of converging at one focal point, light rays merge in a line in front of or behind the retina. Astigmatism can also occur in combination with near-sightedness and far-sightedness.

Result: a distorted view of objects.

In case of astigmatism the laser will remove corneal tissue ellipse-shaped, making the cornea flatter where it is too round and rounder there, where it is too flat.