title: Influence of femtosecond lenticule extraction and small incision lenticule extraction on corneal nerve density and ocular surface: a 1-year prospective, confocal, microscopic study.
abstract: OBJECTIVE
  To compare the influence of femtosecond lenticule extraction (FLEx) and small incision lenticule extraction (SMILE) on corneal nerve density and the ocular surface for equivalent degrees of correction of myopia.
  
  
  METHODS
  Sixty eyes of 30 patients (8 males and 22 females, mean age: 31.0 ± 6.0 years) were included in the study. The patients underwent FLEx in 1 eye and SMILE in the other eye by random assignment. Subbasal nerve density was measured using confocal microscopy preoperatively and at 1 week, 1 and 3 months, and 1 year postoperatively. Ocular surface parameters such as Schirmer's test results, tear film break-up time, and corneal sensation were performed preoperatively and at 1 and 3 months postoperatively.
  
  
  RESULTS
  In the FLEx group, subbasal nerve density was 18,390 ± 6,090 µm/mm(2) preoperatively and 5,770 ± 3,490 µm/mm(2) at 1 year postoperatively (P < .001, Dunnett's test). In the SMILE group, subbasal nerve density was 16,810 ± 6,220 µm/mm(2) preoperatively and 11,870 ± 8,200 µm/mm(2) at 1 year postoperatively (P = .21). The decrease in corneal nerve density was significantly less after SMILE than after FLEx at all postoperative visits (Mann-Whitney U test, P < .05). FLEx resulted in a significant decrease in Schirmer's test results, tear film break-up time, and corneal sensation at all postoperative visits, whereas SMILE induced no significant changes in these parameters (P > .05).
  
  
  CONCLUSIONS
  There was less damage to the sub-basal nerve plexus of the cornea and less effect on the ocular surface parameters after SMILE than after FLEx.
authors.forename: Rie
authors.initials: R
authors.lastname: Ishii
authors.forename: Kimiya
authors.initials: K
authors.lastname: Shimizu
authors.forename: Akihito
authors.initials: A
authors.lastname: Igarashi
authors.forename: Hidenaga
authors.initials: H
authors.lastname: Kobashi
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kamiya
mesh_terms: D000328:Adult; D003315:Cornea / Q000294:innervation* / Q000601:surgery*; D005260:Female; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D018613:Microscopy, Confocal; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies; D016896:Treatment Outcome; D055815:Young Adult