title: [Comparison of the anterior corneal asphericity after small incision lenticule extraction and femtosecond laser in situ keratomileusis].
abstract: OBJECTIVE
  To evaluate and compare the anterior corneal asphericity after small incision lenticule extraction(SMILE)and femtosecond laser in situ keratomileusis(FS-LASIK).
  
  
  METHODS
  In this case-control study, 45 subjects who underwent SMILE operation comprised the study group, and 33 subjects with FS-LASIK operation comprised the control group. The asphericity coefficient Q-value of the right eyes in both groups was measured at diameters of 6, 7, 8 and 9 mm, respectively, before surgery and at 1 day, 1 week, 1 month and 6 months following surgery. The correlation between the variation of Q-value and the central cutting depth was analyzed.
  
  
  RESULTS
  The Q-value of anterior corneal surface was 0.85 ± 0.31, 0.80±0.28, 0.69±0.25 and 0.51±0.23 after SMILE, and 1.13±0.56, 1.01±0.47, 0.80±0.39 and 0.51±0.31 after FS-LASIK at 1 week. In both groups, the Q-value was significantly different before and after surgery(P< 0.05); there were interaction effects between the operation method and time; the difference between the two groups at 6-mm and 7-mm diameters was statistically significant(P<0.05). The variation of the Q-value before and after operation(ΔQ)showed significant difference(P6mm=0.004, P7mm=0.014)between the two groups at 6-mm and 7-mm diameters. The cap diameter of the SMILE group was smaller than that of the FS-LASIK group, but the cutting depth was larger. There was no correlation between ΔQ and the cap/disc diameter. It showed a linear relationship(P<0.05)between ΔQ and the central cutting depth at all examined diameters in the two groups, and the relation degree in the FS-LASIK group was superior to the SMILE group.
  
  
  CONCLUSIONS
  Both SMILE and FS-LASIK operations can change the negative Q-value of the anterior corneal surface to the positive. The impact of SMILE on the asphericity is smaller than that of FS-LASIK. (Chin J Ophthalmol, 2016, 52: 681-685).
authors.affiliation: Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300020, China.
authors.forename: X L
authors.initials: XL
authors.lastname: Su
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: W J
authors.initials: WJ
authors.lastname: Wu
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Wu
authors.forename: Y N
authors.initials: YN
authors.lastname: Wu
authors.forename: C J
authors.initials: CJ
authors.lastname: Yu
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003315:Cornea / Q000033:anatomy & histology* / Q000601:surgery*; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D000072836:Surgical Wound