title: Retrospective Analysis Comparing the Preoperative and Postoperative "Q" Values for 2 Different Lasers in Refractive Surgery.
abstract: OBJECTIVE
  To compare the presurgical and postsurgical corneal asphericity, or "Q value," between VISX Wavefront-guided treatment and Allegretto Wave Wavefront-optimized treatment in photorefractive keratectomy for the correction of myopia.
  
  
  METHODS
  This is a retrospective database analysis performed at the Joint Warfighter Refractive Surgery Center, Lackland Air Force Base, TX. All data were accessed through the Institutional Review Board-approved Joint Warfighter Refractive Surgery Center database. Fifty-one patient records (102 eyes) were reviewed to determine the change in the Q value after photorefractive keratectomy for the correction of myopia.
  
  
  RESULTS
  The average change in the Q value per diopter of treatment sphere over the entire study population was 0.12 (±0.04) for Allegretto and 0.14 (±0.04) for VISX (P = 0.004). There was no statistical difference among the preoperative and postoperative best-corrected visual acuities (BCVAs), low-contrast BCVA (BCVA 5%), or quality of vision complaints between both platforms.
  
  
  CONCLUSIONS
  Low to moderate myopic correction with the Allegretto laser was associated with a smaller change in the Q value per diopter of treatment and therefore more closely maintained the original prolate shape of the cornea when compared with VISX. No difference in the postoperative visual outcome between both groups was detected.
authors.affiliation: *Joint Warfighter Refractive Surgery Center, Lackland AFB, TX; and †14th Medical Operations Squadron, Columbus AFB, MS.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Molchan
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Taylor
authors.forename: Vasudha A
authors.initials: VA
authors.lastname: Panday
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Caldwell
authors.forename: Charles D
authors.initials: CD
authors.lastname: Reilly
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D003315:Cornea / Q000473:pathology*; D003319:Corneal Stroma / Q000601:surgery*; D057108:Corneal Wavefront Aberration / Q000503:physiopathology; D005260:Female; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000295:instrumentation / Q000379:methods*; D011184:Postoperative Period; D057234:Preoperative Period; D012189:Retrospective Studies; D013524:Surgical Flaps; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult