title: Stability after laser in situ keratomileusis in moderately and extremely myopic eyes.
abstract: OBJECTIVE
  To evaluate the stability, mechanism, and degree of regression following laser in situ keratomileusis (LASIK) in cases with moderate to extreme myopia after 2 years of follow-up.
  
  
  METHODS
  Single-center clinical trial.
  
  
  METHODS
  Fifty-two eyes of 38 patients were enrolled in the study. One year follow-up was available for 47 eyes of 35 patients and 2 year follow-up for 39 eyes of 27 patients. Eyes were divided into 2 groups based on the level of preoperative myopia: Group 1, moderate to high myopia > or =15.0 diopters (D) (range -7.0 to -15.0 D, n = 24); Group 2, extreme myopia >15.0 D (range -15.3 to -25.8 D, n = 15). Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper(R) microkeratome and the Summit OmniMed excimer laser. Manifest spherical equivalent, mean central keratometry, and central corneal thickness (CCT) were measured preoperatively and 12 and 24 months postoperatively.
  
  
  RESULTS
  Group 1 exhibited a mild myopic shift (mean -0.07 +/- 0.28 D; P >.2) and a mild increase in keratometry (mean 0.05 +/- 0.46 D; P >.6), with an accompanying increase in CCT (mean 7.5 +/- 12.2 microm; (P =.006) at 24 months. Group 2 displayed a significant myopic shift (mean -0.7 +/- 0.7 D; P =.001) and a significant increase in keratometry (mean 0.4 +/- 0.5 D; P =.01), with a mild increase in CCT (mean 2.4 +/- 9.7 microm; P =.35) at 24 months. Corneal ectasia was evident in 1 eye in the extreme myopia group.
  
  
  CONCLUSIONS
  The refractive effect of myopic LASIK up to -15.0 D remained reasonably stable during the second postoperative year. Significant regression of the refractive effect occurred in eyes with higher levels of myopia (>15.0 D), with the risk of progressive ectasia. Extreme caution is recommended when myopic LASIK is performed in eyes with higher levels of myopia.
authors.affiliation: Centro Oftalmologico de Tijuana, Tijuana, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Magallanes
authors.forename: S
authors.initials: S
authors.lastname: Shah
authors.forename: D
authors.initials: D
authors.lastname: Zadok
authors.forename: A S
authors.initials: AS
authors.lastname: Chayet
authors.forename: K K
authors.initials: KK
authors.lastname: Assil
authors.forename: M
authors.initials: M
authors.lastname: Montes
authors.forename: N
authors.initials: N
authors.lastname: Robledo
mesh_terms: D000328:Adult; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D012029:Refraction, Ocular; D012086:Reoperation; D012449:Safety