Patients withnearsightedness have corneas that are too steep for the length of their eye. The excimer laser is used to flatten the cornea so that the light rays that pass through it come to a point of focus on the retina, rather than in front of it.
Patients withfarsightedness have corneas that are too flat for the length of their eye. The excimer laser is used to steepen the cornea so that the light rays are focused on the retina, rather than behind it.
Inastigmatism, the cornea is elliptical (or football shaped) rather than being round. In this case, the laser reshapes the front surface of the cornea into a rounder shape, again improving the eye's focus.
(c) 2001 Healthology, Inc.