Saad A, et al. – This study aimed to evaluate the currently suggested percentage tissue altered (PTA) metric for its ability to screen for ectasia after laser in–situ keratomileusis (LASIK). It was concluded that the current PTA calculation when applied to a LASIK population with normal preoperative topography and flap thickness measured with ultrasound did not predict the risk for ectasia. Differences between study populations and assumptions might have accounted for the different outcomes obtained in the initially published PTA study.