Why do LASIK, PRK, SMILE, and other corneal refractive surgery cause ectasia and other sight-threatening problems even with the most modern lasers?

All of these procedures work by removing tissue, leaving the cornea permanently thinner. This intrinsically stresses the cornea's structural integrity: these procedures work by weakening the cornea optically -but hopefully not structurally (or at least not very much). This is exactly the opposite of what most people think -that because their vision is made better, the eye must have been strengthened! The higher the degree of nearsightedness you want to treat, the more corneal tissue gets removed. An abnormal, or congenitally weak cornea is going to suffer even more structural compromise than a normal one.

So the "gold standard" in identifying people at risk for ectasia in laser corneal refractive procedures is to 1) not be too aggressive about treating high prescriptions (it is not remotely a matter of surgeon skill), and 2) try to identify, through advanced diagnostic testing of vision and the eye, those patients whose eyes are borderline, or entirely unsuitable for having a cornea-weakening procedure.

J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic