Hi Jennifer! I have literature that states the following. This might help answer your question but your doctor knows what's best for you.....
"Lasik, All-Laser Lasik, PRK, LASEK, and Epi-Lasik all remove corneal tissue to change refractive error. If the patient is myopic, the removal is in the center of the cornea. If the patient is hyperopic, the removal is at the periphery of the cornea. What is most important is that there remains a stable and untouched portion of the cornea to insure corneal integrity and stability.
Studies show and most doctors agree that at least 250 microns of cornea must remain untouched for the cornea to remain stable. More is always better. If too much tissue is removed too deep, the cornea may become unstable and ectasia may develop. This is not something anyone will want to deal with and is most certainly not worth the risk of refractive surgery. It is possible to calculate the amount of tissue that will be removed prior to surgery and take measurements of the cornea to determine with reasonable certainty how much cornea will remain and if this is enough to keep stability."