title: Corneal biomechanical changes in eyes with small incision lenticule extraction and laser assisted in situ keratomileusis.
abstract: BACKGROUND
  Evaluating the corneal biomechanical changes using the Ocular Response Analyzer and the Corvis ST in eyes with incision lenticule extraction (SMILE) and laser assisted in situ keratomileusis (LASIK).
  
  
  METHODS
  This is a retrospective study that included 50 eyes equally divided into two groups. The first group included eyes that underwent SMILE procedure using VisuMax® 500 kHz laser system (Carl Zeiss Meditec, Jena, Germany) and the second group included eyes that underwent LASIK procedure using the EX500 Allegretto excimer laser platform (Wavelight GmbH, Erlangen, Germany). The Ocular Response Analyzer (ORA) and the Corvis ST (CST) measured the corneal biomechanical changes before and after the procedures.
  
  
  RESULTS
  The ORA showed significant decrease of corneal hysteresis (CH) and corneal resistance factor (CRF) in both groups postoperatively. The percentage of change of CH and CRF were found to be significantly higher in group II. There was no significant difference in the IOP with the ORA and the CST pre and postoperatively in either group. Using CST, the deformation amplitude and HC peak distances increased significantly in both groups. It was also noted that the mean percentage of change of the deformation amplitude was nearly five times higher in group II than group I.
  
  
  CONCLUSIONS
  Both LASIK and SMILE substantially decreased the corneal biomechanical properties with greater reduction in the LASIK group.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.|Roayah Vision Correction Center, Alexandria, Egypt.
authors.forename: Ihab Mohamed
authors.initials: IM
authors.lastname: Osman
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt. hany209209@yahoo.com.
authors.forename: Hany Ahmed
authors.initials: HA
authors.lastname: Helaly
authors.affiliation: Roayah Vision Correction Center, Alexandria, Egypt.
authors.forename: Moones
authors.initials: M
authors.lastname: Abdalla
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors.forename: Mohsen Abou
authors.initials: MA
authors.lastname: Shousha
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000502:physiology*; D048988:Corneal Surgery, Laser / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects / Q000379:methods*; D008297:Male; D009216:Myopia / Q000601:surgery; D012189:Retrospective Studies; D055815:Young Adult
keywords: Biomechanics; Corvis ST; LASIK; SMILE