title: Intraindividual comparison of changes in corneal biomechanical parameters after femtosecond lenticule extraction and small-incision lenticule extraction.
abstract: OBJECTIVE
  To compare the biomechanical changes after femtosecond lenticule extraction and small-incision lenticule extraction for myopia.
  
  
  METHODS
  Department of Ophthalmology, Kitasato University, Kanagawa, Japan.
  
  
  METHODS
  Comparative case series.
  
  
  METHODS
  In eyes of consecutive patients, femtosecond lenticule extraction was performed in 1 eye and small-incision lenticule extraction in the other eye (both Visumax laser) by random assignment. Corneal hysteresis (CH) and the corneal resistance factor (CRF) were quantitatively assessed using a dynamic bidirectional applanation device (Ocular Response Analyzer) in relation to the amount of myopic correction preoperatively and 1 week and 1 and 3 months postoperatively.
  
  
  RESULTS
  This study comprised 48 eyes (24 patients). The decrease in CH and the CRF was statistically significant 1 week after both lenticule extraction procedures; however, the changes subsequently stabilized with no further deterioration (P<.001). There were no statistically significant differences between the biomechanical changes in the 2 procedures at any time; however, a significant correlation was found between the changes and the myopic correction 3 months after femtosecond lenticule extraction (r = 0.41, P=.046, CH; r = 0.41, P=.045, CRF) and after small-incision lenticule extraction (r = 0.62, P=.001, CH; r = 0.67, P<.001, CRF).
  
  
  CONCLUSIONS
  The greatest changes in biomechanical parameters occurred within 1 week after femtosecond lenticule extraction and small-incision lenticule extraction; the changes were then nearly stable in relation to the amount of myopic correction. This suggests that the presence or absence of flap lifting does not significantly affect biomechanical parameters.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan. Electronic address: kamiyak-tky@umin.ac.jp.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kamiya
authors.affiliation: From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
authors.forename: Kimiya
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Igarashi
authors.affiliation: From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
authors.forename: Hidenaga
authors.initials: H
authors.lastname: Kobashi
authors.affiliation: From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Sato
authors.affiliation: From the Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Ishii
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D048988:Corneal Surgery, Laser / Q000379:methods*; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008866:Microsurgery / Q000379:methods*; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D014792:Visual Acuity / Q000502:physiology