title: Spot size and quality of scanning laser correction of higher-order wavefront aberrations.
abstract: OBJECTIVE
  To investigate the effect of laser spot size on the outcome of aberration correction with scanning laser corneal ablation.
  
  
  METHODS
  Cleveland Clinic Foundation, Cleveland, Ohio, USA.
  
  
  METHODS
  Corrections of wavefront aberrations of Zernike modes from the second to eighth order were simulated. Gaussian and top-hat beams of 0.6 to 2.0 mm full-width-half-maximum diameters were modeled. The fractional correction and secondary aberration (distortion) were evaluated.
  
  
  RESULTS
  Using a distortion/correction ratio of less than 0.5 as a cutoff for adequate performance, a 2.0 mm or smaller beam was adequate for spherocylindrical correction (Zernike second order), a 1.0 mm or smaller beam was adequate for correction of up to fourth-order Zernike modes, and a 0.6 mm or smaller beam was adequate for correction of up to sixth-order Zernike modes.
  
  
  CONCLUSIONS
  Since ocular aberrations above the Zernike fourth order are relatively insignificant in normal eyes, current scanning lasers with a beam diameter of 1.0 mm or less are theoretically capable of eliminating most higher-order aberrations.
authors.affiliation: Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA. huangd@ccf.org
authors.forename: David
authors.initials: D
authors.lastname: Huang
authors.forename: Muhammad
authors.initials: M
authors.lastname: Arif
mesh_terms: D003198:Computer Simulation; D003315:Cornea / Q000601:surgery*; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D054140:Refractive Surgical Procedures