title: Clinical outcomes of corneal vertex versus central pupil references with aberration-free ablation strategies and LASIK.
abstract: OBJECTIVE
  To compare the clinical outcomes of aberration-free ablation profiles based on the normal corneal vertex (CV) and the pupil center (PC) in relation to laser in situ keratomileusis. Aberration-free aspheric ablation treatments were performed in all cases.
  
  
  METHODS
  Two myopic astigmatism groups (CV centered using the offset between pupil center and normal corneal vertex and PC centered using the pupil center) comprising 24 and 29 eyes (16 and 19 patients), respectively, with a 6-month follow-up, were included. All enrolled eyes had <0.65 mum RMS-higher order aberration (HOA) for 6.00 mm analysis diameter and pupillary offset >200 mum. In all cases, standard examinations, and preoperative and postoperative wavefront analysis were performed. Custom ablation software was used to plan aberration-free aspheric treatments and a flying spot excimer laser system was used to perform ablations. The clinical outcomes were evaluated for predictability, refractive outcome, safety, ocular wavefront aberration, and asphericity.
  
  
  RESULTS
  Of the CV eyes, 38% had improved best spectacle-corrected visual acuity (BSCVA) compared with 24% of the PC eyes (comparison CV/PC P = 0.38). Induced ocular coma was on average 0.17 mum in the CV group and 0.26 mum in the PC group (comparison CV/PC P = 0.01 favoring CV). Induced ocular spherical aberration was on average +0.01 mum in the CV group and +0.07 mum in the PC group (comparison CV/PC P = 0.05 favoring CV). Change in asphericity was on average +0.56 in the CV group and +0.76 in the PC group (comparison CV/PC P = 0.05 favoring CV). No significant shift was observed in the pupillary offset after treatments.
  
  
  CONCLUSIONS
  In myopic eyes with moderate to large pupillary offset, CV-centered treatments performed better in terms of induced ocular aberrations and asphericity, but both centrations were identical in photopic visual acuity.
authors.affiliation: Muscat Eye Laser Center, Muscat, Sultanate of Oman. drmaria@omantel.net.om
authors.forename: Maria Clara
authors.initials: MC
authors.lastname: Arbelaez
authors.forename: Camila
authors.initials: C
authors.lastname: Vidal
authors.forename: Samuel
authors.initials: S
authors.lastname: Arba-Mosquera
mesh_terms: D001251:Astigmatism / Q000601:surgery; D003315:Cornea / Q000033:anatomy & histology*; D019781:Corneal Topography; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D009216:Myopia / Q000601:surgery*; D011680:Pupil / Q000502:physiology*; D012029:Refraction, Ocular / Q000502:physiology; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology