title: Wavefront-guided LASIK for myopia: effect on visual acuity, contrast sensitivity, and higher order aberrations.
abstract: To determine the impact of wavefront-guided LASIK for myopia with or without astigmatism on high and low contrast best spectacle-corrected visual acuity (BSCVA), photopic and mesopic contrast sensitivity, and higher order aberrations.
  
  
  
  Bilateral wavefront-guided LASIK (LADAR-Vision4000; Hansatome microkeratome) was performed on 324 eyes (162 patients) with a mean spherical manifest refraction of -2.84 +/- 1.35 diopters (D) (range: -0.25 to -6.50 D) and astigmatism of -0.81 +/- 0.74 D (range: 0 to -4.00 D). Mean age was 37.7 +/- 9.3 years (range: 20 to 60 years). Best spectacle-corrected visual acuity and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order aberrations were measured using a Shack-Hartmann wavefront sensor, analyzed across a 5-mm pupil. Repeated measures and post hoc analyses determined statistical significance (P < .0025). Only right eyes were analyzed.
  
  
  
  One hundred thirty-six eyes (84%) had uncorrected visual acuity of 20/20 or better 6 months postoperative; 80.9% (131 eyes) were within +/- 0.50 D of attempted correction. Statistically significant postoperative improvements were noted in high and low contrast BSCVA (both P < or = .001); in photopic contrast sensitivity at 3, 6, and 12 cycles per degree (cpd); and in mesopic contrast sensitivity at 12 and 18 cpd (all P < .001). With respect to higher order aberrations, a statistically significant change was seen in Zernike coefficients Z3(-1), Z3(1), Z3(-3), Z3(3), and Z4(4) following surgery (range of mean absolute change: 0.042 to 0.142 microm; all P < or = .001). All increased in magnitude except for Z3(-3), which decreased.
  
  
  
  Despite an increase in higher order aberrations, wavefront-guided LASIK yields excellent visual acuity and contrast sensitivity. Spherical aberration, which increases the most following non-wavefront-guided LASIK, showed no significant change.
authors: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada. njmacdou@uwaterloo.ca
authors: Nancy J
authors: NJ
authors: Keir
authors: Trefford
authors: T
authors: Simpson
authors: Lyndon W
authors: LW
authors: Jones
authors: Desmond
authors: D
authors: Fonn
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000601:surgery; D015350:Contrast Sensitivity / Q000502:physiology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult