title: Influences of Flap Shape and Hinge Angle on Opaque Bubble Layer Formation in Femtosecond Laser-Assisted LASIK Surgery.
abstract: OBJECTIVE
  To evaluate the effects of different flap shapes and hinge angles on opaque bubble layer (OBL) formation using a femtosecond laser for flap creation in LASIK surgery.
  
  
  METHODS
  This retrospective study evaluated 138 eyes of 73 patients who underwent femtosecond laser-assisted LASIK with a 150-kHz IntraLase femtosecond laser (Abbott Medical Optics, Inc., Santa Ana, CA) for myopic astigmatism and compared differences between different flap shapes and hinge angles on OBL formation. The surgical procedures were videotaped, and the patterns and sizes of the OBLs seen during surgery were analyzed. Preoperative and postoperative data including patient demographics, refractive status, keratometry, central corneal thickness, and intraoperative data (flap size and pocket parameters) were recorded. The eyes were divided into four groups based on the corneal flap shape (elliptical versus round) and hinge angle (50° versus 60°).
  
  
  RESULTS
  The preoperative demographic data, mean spherical errors, cylindrical power, and central corneal thickness were not significantly different among the groups. Of the 138 eyes, 107 (77%) developed an OBL covering a mean area of 13.8% ± 12.6% in each case. This area was significantly smaller in the elliptical flap with 60° hinge angle group (P < .05).
  
  
  CONCLUSIONS
  An oval-shaped flap with a larger hinge angle tended to result in less OBL formation in femtosecond laser-assisted LASIK. [J Refract Surg. 2017;33(3):178-182.].
authors.forename: Hung-Yuan
authors.initials: HY
authors.lastname: Lin
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Fang
authors.forename: Ya-Jung
authors.initials: YJ
authors.lastname: Chuang
authors.forename: Han-Chieh
authors.initials: HC
authors.lastname: Yu
authors.forename: Christy
authors.initials: C
authors.lastname: Pu
authors.forename: Yiing-Jenq
authors.initials: YJ
authors.lastname: Chou
authors.forename: Chih-Yi
authors.initials: CY
authors.lastname: Chien
authors.forename: Pi-Jung
authors.initials: PJ
authors.lastname: Lin
authors.forename: Steven C
authors.initials: SC
authors.lastname: Schallhorn
authors.forename: Chi-Chin
authors.initials: CC
authors.lastname: Sun
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis / Q000601:surgery*; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000637:transplantation*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D045423:Microbubbles / Q000009:adverse effects*; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D012029:Refraction, Ocular; D012189:Retrospective Studies; D013524:Surgical Flaps