title: Dry Eye After Small Incision Lenticule Extraction and Femtosecond Laser-Assisted LASIK: Meta-Analysis.
abstract: OBJECTIVE
  To compare postoperative ocular surface integrity and innervation between small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).
  
  
  METHODS
  The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for prospective comparative studies. Trials meeting the selection criteria were quality appraised, and the data were extracted by 2 independent authors. The weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to compare dry eye examinations and corneal subbasal nerve density (SMILE-FS-LASIK).
  
  
  RESULTS
  The study covered 5 trials. No significant difference was found in the Schirmer test score between both groups (WMD = -1.91 and 0.27; 95% CI, -5.02 to 1.20 and -0.99 to 1.54; P = 0.23 and 0.67 at 1- and 6-month follow-ups, respectively). Tear breakup time in the SMILE group significantly exceeded that in the FS-LASIK group (WMD = 0.65 and 1.14; 95% CI, 0.20-1.10 and 0.18-2.10; P = 0.004 and 0.02, at 1- and 6-month follow-ups, respectively). Ocular surface disease index scores were significantly better in the SMILE group 6 months postoperatively (WMD = -10.12, 95% CI, -16.07 to -4.18, P = 0.0008). No significant difference was found in tear osmolarity between both groups (WMD = -5.19 and -6.37; 95% CI, -17.15 to 6.76 and -22.74 to 10.00; P = 0.39 and 0.45 at 1- and 6-month follow-ups, respectively). Higher corneal sensitivity was observed in the SMILE group 1 and 6 months postoperatively (WMD = 11.35 and 3.49; 95% CI, 7.29-15.40 and 1.76-5.21; P < 0.00001 and <0.0001, at 1- and 6-month follow-ups, respectively). Corneal subbasal nerve density was also significantly higher in SMILE-treated eyes than it was in FS-LASIK-treated eyes 1 month postoperatively (WMD = 4.72, 95% CI, 1.10-8.34, P = 0.01).
  
  
  CONCLUSIONS
  According to this meta-analysis, the SMILE procedure has fewer negative impacts on the ocular surface and corneal innervation than does FS-LASIK. Furthermore, SMILE shows superiority over FS-LASIK by a exhibiting a lower risk of postoperative dry eye.
authors: *Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan; and †Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA.
authors: Hidenaga
authors: H
authors: Kobashi
authors: Kazutaka
authors: K
authors: Kamiya
authors: Kimiya
authors: K
authors: Shimizu
mesh_terms: D001251:Astigmatism / Q000601:surgery*; D003315:Cornea / Q000294:innervation / Q000473:pathology; D015352:Dry Eye Syndromes / Q000209:etiology* / Q000473:pathology; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects* / Q000379:methods; D054018:Lasers, Excimer / Q000009:adverse effects / Q000627:therapeutic use; D009216:Myopia / Q000601:surgery*; D011446:Prospective Studies; D013666:Tears / Q000737:chemistry / Q000378:metabolism