This video investigates the association of a novel metric, percent tissue altered (PTA), with the occurrence of ectasia after LASIK in eyes with normal corneal topography and compares this metric to other recognized risk factors. PTA is derived from the equation [(flap thickness + ablation depth)/preoperative corneal thickness] or PTA = [(FT + AD)/CCT]. This video reveals the higher association of PTA with the occurrence of post-LASIK ectasia in eyes with normal preoperative corneal topography compared with other recognized risk factors.