title: Posterior corneal ectasia following LASIK.
abstract: OBJECTIVE
  To evaluate the cases of posterior corneal ectasia following laser in situ keratomileusis.
  
  
  METHODS
  Thirteen eyes of 7 patients, that were diagnosed to have posterior corneal ectasia (ł0.060 mm) on Orbscan topographic system following LASIK, were identified. The parameters evaluated were uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), refraction, contrast sensitivity, glare, corneal topography, keratometry and pachymetry. The preoperative and postoperative data at day 1, 1 week, 1 month, 3 months, 6 months and 1 year were retrospectively analyzed.
  
  
  RESULTS
  The mean UCVA of the patients before LASIK surgery was 0.032 +/- 0.04. It was 0.320 +/- 0.159 in follow-up of LASIK surgery after 1 year. The mean Pre-LASIK BCVA was 0.59 +/- 0.11. There was no change in mean BCVA at 1 year. The mean preoperative spherical equivalent was -14.25 +/- 2.91 D except in 2 hyperopic eyes in which the mean spherical equivalent preoperatively was +5.75 +/- 0.35 D. The mean postoperative spherical equivalent after 1 year of LASIK surgery in last follow-up (+/- enhancement) was - 3.45 +/- 2.08 in the myopic eyes and + 1.0 +/- 0.70 in the two hyperopic eyes. The mean preoperative posterior corneal elevation was 0.022 +/- 0.011 mm, which at the end of 1 week following LASIK was 0.067 +/- 0.009 and at 1 year/ last follow-up following LASIK, it was 0.068 +/- 0.006 mm.
  
  
  CONCLUSIONS
  Higher amplitudes of refractive correction may lead to the occurrence of posterior corneal ectasia.
authors.affiliation: Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi.
authors.forename: Rasik B
authors.initials: RB
authors.lastname: Vajpayee
authors.forename: Rajesh
authors.initials: R
authors.lastname: Sinha
authors.forename: Namrata
authors.initials: N
authors.lastname: Sharma
authors.forename: Jeewan S
authors.initials: JS
authors.lastname: Titiyal
authors.forename: Radhika
authors.initials: R
authors.lastname: Tandon
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000473:pathology*; D004108:Dilatation, Pathologic / Q000209:etiology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D008297:Male; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D014792:Visual Acuity