title: Changes in corneal deformation parameters after lenticule creation and extraction during small incision lenticule extraction (SMILE) procedure.
abstract: OBJECTIVE
  To investigate the effects of lenticule creation and subsequent corneal lenticule extraction on corneal deformation parameters during small incision lenticule extraction (SMILE) procedure.
  
  
  METHODS
  In this prospective study, 18 eyes of 10 patients (27.90 ± 7.11 years, -5.64 ± 2.45 diopters) scheduled for SMILE procedure were enrolled. Changes in the corneal deformation parameters, including deformation amplitude (DA), applanation time(AT1 and AT2), applanation length(AL1 and AL2), corneal velocity(CV1 and CV2), peak distance(P.Dist.), radius and intraocular pressure values were measured preoperatively, immediately after lenticule creation and subsequent to corneal lenticule extraction in all eyes with the Corvis Scheimpflug Technology (Corvis ST, OCULUS, Wetzlar, Germany). Repeated measures analysis of variance (ANOVA) with bonferroni-adjusted post hoc comparisons was performed to investigate changes following each step of the procedure.
  
  
  RESULTS
  All surgical procedures were uneventful. A significant difference was detected among the three time points (pre-operation, post-lenticule creation and post lenticule extraction) for AT1 (P<0.001), AT2 (P = 0.001), DA(P<0.001), and IOP(P = 0.002). Bonferroni-adjusted post hoc comparisons indicated that there was no significant change in AT1, AT2, DA, or IOP after lenticule creation (post hoc P>0.05), but there was a significant change in these parameters following subsequent corneal lenticule extraction (post hoc P<0.01), when compared to values obtained pre-operatively. The scheimpflug camera of the Corvis ST demonstrated the intralamellar small gas bubbles formed from the vaporisation of tissue after lenticule creation and a gray zone was observed between the cap and the residual stromal bed after lenticule extraction.
  
  
  CONCLUSIONS
  There is a significant change in corneal deformation parameters following SMILE procedure. The changes may be caused predominantly by stromal lenticule extraction, while lenticule creation with femtosecond laser may not have an obvious effect on corneal deformation properties.
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Peijun
authors.initials: P
authors.lastname: Yao
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Huamao
authors.initials: H
authors.lastname: Miao
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Niu
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Lab of Myopia, Ministry of Health, Department of Ophthalmology, EYE & ENT Hospital of Fudan University, Shanghai, China.
authors.forename: Xingtao
authors.initials: X
authors.lastname: Zhou
mesh_terms: D000328:Adult; D003319:Corneal Stroma / Q000601:surgery*; D048988:Corneal Surgery, Laser / Q000379:methods; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000601:surgery; D011184:Postoperative Period; D057234:Preoperative Period; D011446:Prospective Studies; D055815:Young Adult