One Picture is Worth a Thousand Words

www.dishler.com/pages/technology#zywave

Here we see the Zywave of a patient who has over 6 diopters of astigmatism.  This 3-D representation shows the map of the astigmatism in the circle at the bottom of the "cube".  The red/orange color is the steeper area, whereas the blue color represents the flatter areas as in a traditional topography exam.  This is actually a wavefront examination, and what is really being shown is the delay in light reaching the sensors due to the astigmatism created by the entire eye optical system.  When we look at this three dimensionally, we see an image that looks much like a saddle.  This is the actual effect that the astigmatism has on the eye.  In "wavefront optimized" ablation, we take this wavefront into account in order to repair the shape of the eye to a more normal shape which will create a more perfect wavefront.  From a vision perspective it is most important to have the wavefront correct which is more related to how the eye actually sees than the basic shape itself.  These understandings have helped to improve the results of LASIK to our current ability to treat even this amount of astigmatism successfully.  This patient had a return of excellent vision in spite of the large amount of astigmatism present.