title: Flap-induced refraction change in LASIK after penetrating keratoplasty.
abstract: OBJECTIVE
  To further analyze the refractive and topographic changes occurring with microkeratome lamellar keratotomy and to investigate possible factors associated in eyes with previous penetrating keratoplasty (PK).
  
  
  METHODS
  The Hansatome microkeratome was used to create a lamellar corneal flap in 21 eyes of 19 patients after PK. The laser ablation was not performed in the first stage. Pre- and postoperative refractions and corneal topographies were compared to evaluate possible changes induced by the keratotomy.
  
  
  RESULTS
  Twenty-one eyes were analyzed in this study. Mean time between PK and lamellar keratotomy was 36.63 +/- 28.23 months (range: 12 to 120 months). No microkeratome-related flap complications occurred. Previous to the keratotomy, the mean spherical equivalent refraction was -4.26 +/- 3.41 diopters (D), mean refractive astigmatism was -4.71 +/- 2.27 D, and mean topographic astigmatism was 5.28 +/- 2.94 D. After keratotomy, eyes showed statistically significant changes in spherical equivalent refraction from preoperative values (P = .025), with 3 eyes showing changes > 2.00 D. Average refractive and topographic astigmatism did not change significantly from before to after keratotomy. However, surgically induced astigmatism (SIA) calculated through vector analysis was > 1.01 in 11 (52.4%) eyes. A statistically significant correlation was found between the SIA values and preoperative refractive astigmatism (P = .025).
  
  
  CONCLUSIONS
  Lamellar keratotomy as part of two-stage LASIK in eyes with prior PK led to refractive changes that justify the use of this technique, especially in eyes with high degrees of preoperative astigmatism.
authors: Eye Clinic Day Hospital, São Paulo, Brazil. telma.pereira@uol.com.br
authors: Telma
authors: T
authors: Pereira
authors: Adriana S
authors: AS
authors: Forseto
authors: Gustave Nosé
authors: GN
authors: Alberti
authors: Walton
authors: W
authors: Nosé
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000209:etiology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000601:surgery*; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D015948:Keratoplasty, Penetrating; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012029:Refraction, Ocular; D013524:Surgical Flaps / Q000473:pathology*