title: Efficacy of laser in situ keratomileusis in correcting anterior and non-anterior corneal astigmatism: comparative study.
abstract: OBJECTIVE
  To compare the efficacy of conventional laser in situ keratomileusis (LASIK) in treating corneal astigmatism and in treating noncorneal ocular residual astigmatism.
  
  
  METHODS
  Private practice, Nashville, Tennessee, USA.
  
  
  METHODS
  Retrospective case series.
  
  
  METHODS
  The records of dominant eyes of consecutive patients who had LASIK were retrospectively analyzed to compare the efficacy of LASIK in eyes with predominantly anterior corneal astigmatism with the efficacy in eyes with predominantly ocular residual astigmatism (ORA). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Preoperatively, the ratio of ORA to preoperative refractive cylinder (R) was used to divide the patients into 2 groups; that is, eyes with predominantly anterior corneal astigmatism (ORA/R ratio <1.0) and eyes with predominantly ORA (ORA/R ratio ≥1.0). Efficacy was determined by examining the magnitude of the remaining uncorrected astigmatism and comparing the index of success (proportion of preoperative refractive astigmatism that remained uncorrected by LASIK) between the 2 groups.
  
  
  RESULTS
  The study evaluated 61 eyes of 61 patients. Conventional LASIK was twice as efficacious in the low-ORA group as in the high-ORA group. The index of success was 0.24 and 0.50, respectively, and the difference between groups was statistically significant (P = .036).
  
  
  CONCLUSIONS
  The efficacy of astigmatic correction by LASIK was significantly higher in eyes in which the preoperative refractive astigmatism was located mainly on the anterior corneal surface than in eyes in which it was mainly located posterior to the anterior corneal surface.
authors.affiliation: Wang Vision Institute, Nashville, Tennessee, USA. lkugler@me.com
authors.forename: Lance
authors.initials: L
authors.lastname: Kugler
authors.forename: Ilan
authors.initials: I
authors.lastname: Cohen
authors.forename: Walid
authors.initials: W
authors.lastname: Haddad
authors.forename: Ming X
authors.initials: MX
authors.lastname: Wang
mesh_terms: D000328:Adult; D000869:Anterior Eye Segment / Q000503:physiopathology / Q000601:surgery; D001251:Astigmatism / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology