Chapter twelve discusses keratoectasia, which is an iatrogenic keratoconus after refractive laser surgeries such as PRK and Lasik. Incidence, diagnosis, biomechanics, and risk factors of this disease are all mentioned in details. Talking about the risk factors includes high myopia, thin cornea, low residual stromal bed thickness (RSB), young age, ectatic corneal disorders and Forme Fruste keratoconus, and others. Recommendations from the Joint AAO/ISRS/ASCRS committee on corneal ectasia after Lasik and \"Ectasia risk-scoring system\" are also mentioned.