title: Corneal biomechanical effects: small-incision lenticule extraction versus femtosecond laser-assisted laser in situ keratomileusis.
abstract: OBJECTIVE
  To compare the biomechanical properties of the cornea after small-incision lenticule extraction (lenticule extraction group) with those after femtosecond laser-assisted laser in situ keratomileusis (femtosecond LASIK group).
  
  
  METHODS
  Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China.
  
  
  METHODS
  Prospective comparative case series.
  
  
  METHODS
  Corneal hysteresis (CH), the corneal resistance factor (CRF), and 37 other biomechanical waveform parameters were quantitatively assessed with the Ocular Response Analyzer preoperatively and 1 week and 1, 3, and 6 months postoperatively.
  
  
  RESULTS
  Each group comprised 40 eyes. The decrease in CH and the CRF was statistically significant 1 week postoperatively compared with preoperatively in both groups (P<.0001). However, the CH and CRF values in the lenticule extraction group were significantly higher than those in the femtosecond LASIK group 3 months and 6 months postoperatively (P<.032). The residual stromal thickness index versus the CRF and CH and the planned lenticule thickness versus the change in central corneal thickness were statistically significant in the lenticule extraction group (r = 0.388 to 0.950, P<.018); no significant correlation was found in the femtosecond LASIK group. In the waveform analysis of the lenticule extraction group, 28 of the 37 biomechanical waveform parameters differed significantly between preoperative values and postoperative values (P<.035).
  
  
  CONCLUSIONS
  Both small-incision lenticule extraction and femtosecond laser-assisted LASIK can cause biomechanical changes in the cornea. However, changes in the cornea's viscoelastic properties were less after lenticule extraction than after LASIK.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.affiliation: From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China. Electronic address: wangyan7143@vip.sina.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China.
authors.forename: Shengsheng
authors.initials: S
authors.lastname: Wei
authors.affiliation: From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Tang
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery; D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D048988:Corneal Surgery, Laser / Q000379:methods; D019781:Corneal Topography; D004108:Dilatation, Pathologic / Q000503:physiopathology; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; 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; D055815:Young Adult