title: Randomized, contralateral eye study to evaluate the effect of standard and inverted side-cut angle on corneal biomechanical properties during femtosecond laser-assisted in situ keratomileusis.
abstract: OBJECTIVE
  To evaluate the effect of side-cut angle profile on corneal biomechanical properties after femtosecond laser in situ keratomileusis (FS-LASIK).
  
  
  METHODS
  Ninety-six myopic eyes of 48 patients underwent FS-LASIK. One eye of each patient was randomized to flap creation with a side-cut angle of 115°. The fellow eye flap side-cut angle was adjusted to 70°. Mean absolute error of flap diameter and mean change in Goldmann-correlated intra-ocular pressure (IOPg), corneal-compensated IOP (IOPcc), corneal hysteresis (CH), corneal resistance factor (CRF), p1 area, p2 area, p1 area 1 and p2 area 1 were compared between both groups.
  
  
  RESULTS
  Overall, the mean IOPg and CRF showed significant reduction at the end of 1 and 3 months, as well as between 1 and 3 months postoperatively (p ≤ 0.03). The mean IOPcc and CH showed significant reduction (p < 0.001) at the end of 3 months postoperatively. The parameters p1 area, p2 area, p1 area 1 and p2 area 1 changed significantly at the end of 1 and 3 months postoperatively (p < 0.001). There was no significant difference between both groups with regards to the mean change of IOPg, IOPcc, CH, CRF, p1 area, and p1 area 1. In 115° group, the mean absolute error in flap diameter was greater compared with 70° group (p = 0.014).
  
  
  CONCLUSIONS
  The stability of IOP and corneal biomechanical properties were not enhanced in FS-LASIK flaps with an inverted side-cut angle. The size of corneal flap created with 70° side-cut angle was more accurate compared with 115° side-cut angle.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Kowloon, Hong Kong, China.
authors.forename: Yolanda W Y
authors.initials: YW
authors.lastname: Yip
authors.forename: Marco C Y
authors.initials: MC
authors.lastname: Yu
authors.forename: Vishal
authors.initials: V
authors.lastname: Jhanji
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D003319:Corneal Stroma / Q000601:surgery; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D013524:Surgical Flaps; D055815:Young Adult
keywords: corneal biomechanics; femtosecond lasik; ocular response analyser; side-cut angle