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
  Numerical simulation of ablation outcome.
  
  
  RESULTS
  Correction of wavefront aberrations of Zernike modes from 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. Using a distortion/correction ratio of less than 0.5 as a cutoff for adequate performance, we found that a 2 mm or smaller beam is adequate for spherocylindrical correction (Zernike second order), a 1 mm or smaller beam is adequate for correction of up to fourth order Zernike modes, and a 0.6 mm or smaller beam is adequate for correction of up to sixth order Zernike modes.
  
  
  CONCLUSIONS
  Since ocular aberrations above Zernike fourth order are relatively insignificant, current scanning lasers with a beam diameter of 1 mm or less are theoretically capable of eliminating most of the higher order aberrations of the eye.
authors.affiliation: Cleveland Clinic Foundation, OH 44195, USA. huangd@ccf.org
authors.forename: D
authors.initials: D
authors.lastname: Huang
authors.forename: M
authors.initials: M
authors.lastname: Arif
mesh_terms: D003198:Computer Simulation; D003315:Cornea / Q000601:surgery*; D006801:Humans; D054018:Lasers, Excimer; D008954:Models, Biological; D018903:Photorefractive Keratectomy / Q000379:methods*; D054140:Refractive Surgical Procedures