Retrospectively review the medical records of all patients who underwent refractive surgery referred from the out-patient clinic of Tanta University hospital between September 2015 and September 2020 .~Data collection will include:~Preoperative and postoperative Evaluation: Age, sex, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest and cycloplegic refraction, Slit lamp biomicroscopy, fundus examination.~Data of Corneal Tomography keratometric using Scheimpflug camera (Pentacam Oculus- Germany) :that includes the following indices~Average keratometric value (K mean) in diopters~Maximum simulated keratometry (Kmax) in diopters~Index of Surface Variance (ISV) in microns~Index of Vertical Asymmetey (IVA) in microns~Radii Minimum (R min) in microns~Index of height asymmetry (IHA) in microns~Index of height decantation (IHD) in microns~Aberration coefficient (ABR)~The data of the pentacam will be collected pre-operative and analyzed at 1 month, 3 months and 6 months with recording of the complications.
To evaluate the changes that occur in the corneal indices after corneal refractive surgery either PRK or LASIK.