title: [Difficulties in lenticule extraction during small incision lenticule extraction with the continuous curvilinear lenticulerrhexis technique].
abstract: OBJECTIVE
  To investigate the incidence rate, classification, and management of difficulties in lenticule extraction during small incision lenticule extraction (SMILE) with the continuous curvilinear lenticulerrhexis (CCL) technique, and surgical safety and efficacy.
  
  
  METHODS
  Retrospective study. A total of 342 continuous subjects (680 eyes) received surgical treatment by the same surgeon using the SMILE-CCL technique. The separation was performed only between the cap and anterior surface of the lenticule (8 to 2 o'clock) and at the edge between the cap and posterior surface of the lenticule (1 o'clock). The lenticule was then extracted in a clockwise motion using the CCL technique. Cases with lenticule extraction difficulties were observed through surgery videos. Classification and management of the difficulties were recorded. The rate of intact lenticule extraction was calculated.
  
  
  RESULTS
  Twenty-two subjects (22 eyes) had lenticule extraction difficulties. The rate was 3.24%. No difficulty was found in side cut lifting. The microforceps grip loss occurred more than once in five eyes. It was difficult to separate the cap and anterior surface in 12 eyes. One eye had a microdefect in the margin of the lenticule. Five eyes were observed to have single side tearing of side cut. No eyes had double sides tearing of side cut. The microforceps were changed when grip loss occurred more than once. When there were separation difficulties, the pace of lenticule extraction was slowed down, with tearing through the tangential direction of the circle (clockwise). The conventional technique was used in three cases with severe difficulties. All lenticules were successfully extracted from the 22 eyes (100%). Uncorrected visual acuity was ≥1.0 in all eyes at 1 day after surgery. The safety index (the ratio between best corrected visual acuity at 1 month and preoperatively) was 1.11. The efficacy index (the ratio between uncorrected visual acuity at 1 month and preoperative best corrected visual acuity) was 1.04.
  
  
  CONCLUSIONS
  Difficulties in lenticule extraction occur during SMILE-CCL with a low incidence. Various difficulties can be managed with different techniques. There are no extra effects on surgical safety and efficacy. It is safe and effective to switch back to the conventional technique when severe lenticule extraction difficulties occur.
authors.affiliation: Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Key Laboratory of Health Ministry for Myopia, Shanghai 200031, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Qin
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhao
authors.forename: Meiyan
authors.initials: M
authors.lastname: Li
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.forename: Renyuan
authors.initials: R
authors.lastname: Chu
authors.forename: Xingtao
authors.initials: X
authors.lastname: Zhou
mesh_terms: D003319:Corneal Stroma / Q000601:surgery*; D006801:Humans; D054140:Refractive Surgical Procedures / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D014792:Visual Acuity