title: Comparison of clinical results between flap-on and flap-off techniques of epithelial-laser in situ keratomileusis in correction of low to moderate myopia in eyes with thin corneas.
abstract: OBJECTIVE
  To prospectively compare flap-on and flap-off techniques of epithelial-laser in situ keratomileusis (epi-LASIK) for the correction of low to moderate myopia in patients with thin corneas.
  
  
  METHODS
  In this randomized, interventional study, the cohort was comprised of 88 eyes (44 patients) with myopia which underwent epi-LASIK. The epithelium was separated as a 9 mm flap with 2-4 mm nasal hinge with epikeratome (Lasatom, Gebauer Medizintechnik GmbH, Neuhausen, Germany) and the ablation was performed with the MEL 80 excimer laser (Carl Zeiss, Meditec, Jena, Germany). Thirty-eight eyes underwent flap-on Epi-LASIK where the flap was repositioned after ablation (flap-on group) and 50 eyes underwent flap-off Epi-LASIK where the epithelial flap was discarded (flap-off group). Pre- and post-operative uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), and spherical equivalent (SE) were collected for each group. Post-operative pain, time to epithelialization, and corneal haze were also collected postoperatively. Variables were compared with the paired t-test, chi-squared test and one-way analysis of variance. Statistically significance was indicated by p < 0.05.
  
  
  RESULTS
  The mean preoperative SE was -3.89 ± 1.9 diopters (D) for the flap-on group and -3.92 ± 2.17 D for the flap-off group (p = 0.96). The mean follow-up was 12 months. The mean pain score was comparable on all postoperative days except the 2nd postoperative day where the flap-on had significantly lower mean pain scores (p = 00). Time for epithelial healing was 4.39 ± 0.49 days in flap-on group and 4.64 ± 0.69 days in flap-off group (p = 0.07). There was no significant difference in the postoperative UCVA between groups (p = 0.77). Corneal haze at the end of postoperative follow-up was not different between groups (p = 0.217).
  
  
  CONCLUSIONS
  There is no significant difference in the clinical outcomes between flap-on and flap-off techniques of Epi-LASIK for the correction of low to moderate myopia.
authors: Ophthalmology Center, Al-Thawra Modern General Teaching Hospital, Faculty of Medicine, Sana'a University, PO Box 12272, Sana'a, Yemen.
authors: Aziz
authors: A
authors: Shaher
authors: Yahia
authors: Y
authors: Al-Gassaly
authors: Horia
authors: H
authors: Alansy
authors: Tawfik
authors: T
authors: Alkhatib
keywords: Flap-off epi-lasik; Flap-on epi-lasik; Myopia; Refractive surgery
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