title: Outcome of corneal and laser astigmatic axis alignment in photoastigmatic refractive keratectomy.
abstract: OBJECTIVE
  To compare the refractive results of laser astigmatic treatment in eyes in which the astigmatic axes of the eye and laser are aligned by limbal marking at the 6 o'clock position and in eyes that are not marked.
  
  
  METHODS
  University Hospital and Clinics, Madison, Wisconsin, USA.
  
  
  METHODS
  This retrospective study comprised 143 eyes that had photoastigmatic refractive keratectomy with the VISX Star excimer laser. The eyes were divided into marked (G1) and unmarked (G2) groups. Based on the preoperative astigmatism, each group was subdivided into low astigmatism (</=1.00 diopter [D]) and high astigmatism (>/=1.25 D). Early postoperative manifest refractions (1.0 to 2.5 months) were analyzed. The Alpins vector analysis method was used to calculate the target induced astigmatism, surgically induced astigmatism, difference vector (DV), magnitude of error (ME), angle of error (AE), and index of success (IS).
  
  
  RESULTS
  There was no significant difference between the groups in DV, ME, and IS. When the subgroups were analyzed, the DV and ME were comparable; the IS in the G1 high astigmatism subgroup was significantly better than that in the G2 high astigmatism subgroup (0.22 +/- 0.08 and 0.29 +/- 0.04, respectively; P <.0001). There was comparable scatter of AE values; 30% and 36% in G1 and G2, respectively, had an AE of 0. Similar scatter was observed in the subgroups. Of the eyes that had an AE of 0, 90% and 43% in the high astigmatism subgroups of G1 and G2, respectively (P <.05), had full correction of astigmatism.
  
  
  CONCLUSIONS
  Limbal marking and subsequent eye and laser astigmatic axis alignment improved the refractive outcome of laser astigmatic treatment of >/=1.25 D. A preliminary report of an ongoing prospective randomized study of eyes that had laser in situ keratomileusis is included.
authors.affiliation: Cornea Service, Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Farah
authors.forename: E
authors.initials: E
authors.lastname: Olafsson
authors.forename: D G
authors.initials: DG
authors.lastname: Gwynn
authors.forename: D T
authors.initials: DT
authors.lastname: Azar
authors.forename: F S
authors.initials: FS
authors.lastname: Brightbill
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000601:surgery*; D003315:Cornea / Q000033:anatomy & histology* / Q000601:surgery; D006801:Humans; D054018:Lasers, Excimer; D008875:Middle Aged; D009216:Myopia / Q000601:surgery; D018903:Photorefractive Keratectomy / Q000379:methods; D012029:Refraction, Ocular; D012189:Retrospective Studies; D016896:Treatment Outcome