title: Induced optical aberrations following formation of a laser in situ keratomileusis flap.
abstract: OBJECTIVE
  To determine how refractive error, visual acuity, and high-order aberrations (3rd- and 4th-order) are affected by the formation of a lamellar corneal flap during laser in situ keratomileusis (LASIK).
  
  
  METHODS
  University refractive surgery center.
  
  
  METHODS
  The effect of lamellar corneal flap formation was analyzed in 15 myopic eyes (mean preoperative refraction -4.72 diopters [D] [range -1.25 to -7.25 D]). The flap was created using a 2-step procedure: (1). a nasally hinged lamellar corneal flap was created; (2). the flap was lifted and stromal ablation performed 2 months after the flap was made. A Hartmann-Shack aberrometer was used to measure the aberrations.
  
  
  RESULTS
  There was no significant change in the refractive error (spherical equivalent pre-flap -4.72 +/- 1.99 D and post-flap -4.62 +/- 1.99 D [P =.28]) or visual acuity (pre-flap uncorrected visual acuity [UCVA] 0.07 and best corrected visual acuity [BCVA] 0.96; post-flap UCVA 0.08 and BCVA 0.95 [P =.16 and P =.33, respectively]). A statistically significant increase in total higher-order wavefront aberrations was observed following flap formation (root mean square pre-flap 0.344 +/- 0.125 and post-flap 0.440 +/- 0.221 [P =.04]).
  
  
  CONCLUSIONS
  Flap formation during LASIK can modify the eye's existing natural higher-order aberrations (especially spherical and coma-like aberrations along the axis of the flap's hinge), while visual acuity and refractive error remain unaffected.
authors.affiliation: Department of Ophthalmology, Vardinoyannion Eye Institute of Crete, University of Crete, Heraklion, Greece. pallikar@med.uoc.gr
authors.forename: Ioannis G
authors.initials: IG
authors.lastname: Pallikaris
authors.forename: George D
authors.initials: GD
authors.lastname: Kymionis
authors.forename: Sophia I
authors.initials: SI
authors.lastname: Panagopoulou
authors.forename: Charalambos S
authors.initials: CS
authors.lastname: Siganos
authors.forename: Michalis A
authors.initials: MA
authors.lastname: Theodorakis
authors.forename: Aristofanis I
authors.initials: AI
authors.lastname: Pallikaris
mesh_terms: D001251:Astigmatism / Q000209:etiology*; D003319:Corneal Stroma / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D009216:Myopia / Q000601:surgery*; D011446:Prospective Studies; D013524:Surgical Flaps / Q000009:adverse effects*; D014786:Vision Disorders / Q000209:etiology*; D014792:Visual Acuity