title: The change in internal aberrations following myopic corneal laser refractive surgery.
abstract: BACKGROUND
  In virgin eyes, the internal aberrations compensate corneal aberrations, and it has been suggested that the compensation may be feedback-driven and developmental, with active or passive adaptive mechanisms potentially responsible for the aberration auto-compensation. The purpose of this study is to investigate the internal higher order aberrations (HOA) following laser in situ keratomileusis (LASIK).
  
  
  METHODS
  Prospective corneal and internal HOA were measured pre-operatively and 6 months post-operatively on 50 consecutive LASIK patients with the OPD-Scan.
  
  
  RESULTS
  There were increases to corneal HOA terms Z⁰₄ (0.215 ± 0.092 μm to 0.381 ± 0.180 μm), Z⁰₆ (0.002 ± 0.018 μm to 0.049 ± 0.034 μm) and Z⁴₆ (0.010 ± 0.017 μm to 0.018 ± 0.016 μm) with corresponding increases to internal HOA terms Z⁰₄ (-0.176 ± 0.102 μm to -0.218 ± 0.121 μm), Z⁰₆ (0.004 ± 0.022 μm to -0.010 ± 0.036 μm) and Z⁴₆ (0.008 ± 0.106 μm to -0.015 ± 0.054 μm). The increases in internal aberrations attenuated the increase in corneal aberrations, providing an overall lower quantity of total aberration. A greater increase in corneal spherical aberration and associated compensation was found to occur with greater degrees of attempted myopic correction.
  
  
  CONCLUSIONS
  Corneal spherical aberration and Z⁴₆increased with corresponding increases in the internal spherical aberration and Z⁴₆ following LASIK. This may be an active compensatory mechanism of the internal optics to change, in order to reduce the effect of induced corneal HOA.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, BT52 1SA, UK. colm.mcalinden@gmail.com
authors.forename: Colm
authors.initials: C
authors.lastname: McAlinden
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Moore
mesh_terms: D000328:Adult; D003319:Corneal Stroma / Q000473:pathology / Q000601:surgery*; D057108:Corneal Wavefront Aberration / Q000209:etiology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D011446:Prospective Studies; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult