Purpose The aim of this study was to determine the prevalence and risk factors of post-laser in situ keratomileusis (post-LASIK) ectasia in an Egyptian population sample.
Design This is a retrospective case–control study.
Patients and methods The study included 44 patients, who were classified into two groups. The first group (post-LASIK ectasia) included 31 eyes (18 patients) and the second group (LASIK without complications) included 52 eyes (26 patients). The comparison between the two groups included the pre-LASIK refractive error, corrected distance visual acuity (CDVA), corneal curvature, corneal thickness, corneal elevations, ectasia risk scoring, flap thickness, and residual stroma after LASIK. We also evaluated the changes that occurred in patients with ectasia in comparison to their pre-LASIK parameters.
Results The prevalence of post-LASIK ectasia was 0.22%. The degree of myopia, astigmatism, maximum keratometry reading (K-max), ectasia risk scoring, and flap lift for retreatment were significantly higher in the ectasia group compared with the control group (P=0.041, 0.006, 0.016, 0.038, and 0.017, respectively), while the CDVA and residual stroma after LASIK were significantly less in the ectasia group (P=0.039 and 0.003, respectively). There was a statistically significant increase in astigmatism and change in its type and increased K-max and corneal elevations after ectasia.
Conclusions The degree of myopia, astigmatism, CDVA, K-max, ectasia risk scoring, residual stroma after LASIK, and retreatment are risk factors for ectasia development.

Keywords: corneal ectasia, laser in situ keratomileusis complications, laser in situ keratomileusis, post-laser in situ keratomileusis ectasia