title: Causes of decentration after laser-assisted subepithelial keratectomy.
abstract: OBJECTIVE
  To determine important factors causing decentration after laser-assisted subepithelial keratectomy (LASEK).
  
  
  METHODS
  A total of 223 cases (446 eyes) were evaluated after LASEK using corneal topography to determine the amount of decentration. Decentration and pupillary offset values and their components on the nasal, temporal, superior, and inferior axes were analyzed with the t test and the two-way repeated measures analysis of variance test in patients with myopia or hypermetropia. Correlation analysis between the amount of decentration and the possible determinative variables (age, gender, spherical refractive error, magnitude of astigmatism, spherical equivalent, average keratometry, mesopic pupil diameter, decentration, and pupillary offset) were performed.
  
  
  RESULTS
  Although decentration up to 0.99 mm was observed, mean decentration was 0.26 ± 0.16 mm. Alternatively, pupillary offset values were higher and the mean pupillary offset was 0.28 ± 0.16 mm. In myopia, mean total decentration was significantly less than hyperopia (P = .001). The inferior component of decentration was higher than the other locations in both myopia and hypermetropia. The nasal component of pupillary offset was highest among others. When all cases were included in the analysis, Pearson correlation analysis showed a statistically significant correlation between decentration and presence of hyperopia (r = 0.162 and P =.001) and amount of pupillary offset (r = 0.296 and P = .001).
  
  
  CONCLUSIONS
  Mean decentration was higher in hyperopia than in myopia. Most of the decentration may be attributed to inferior decentration. Pupillary offset values were the factor most significantly correlated to the amount of decentration in all cases.
authors.affiliation: Ankara Ataturk Training and Research Hospital First Ophthalmology Clinic, Ankara, Turkey.
authors.forename: Hasan Basri
authors.initials: HB
authors.lastname: Cakmak
authors.forename: Nurullah
authors.initials: N
authors.lastname: Cagil
authors.forename: Huseyin
authors.initials: H
authors.lastname: Simavli
authors.forename: Sirin
authors.initials: S
authors.lastname: Serefli
authors.forename: Saban
authors.initials: S
authors.lastname: Simsek
mesh_terms: D000328:Adult; D003316:Corneal Diseases / Q000175:diagnosis / Q000209:etiology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000150:complications / Q000601:surgery*; D049008:Keratectomy, Subepithelial, Laser-Assisted; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000150:complications / Q000601:surgery*; D011183:Postoperative Complications; D011680:Pupil / Q000502:physiology; D012189:Retrospective Studies; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology*; D055815:Young Adult