title: Effect of hinged lamellar keratotomy on post-keratoplasty astigmatism and vision.
abstract: OBJECTIVE
  To show that hinged lamellar keratotomy alone affects refraction and vision in post-keratoplasty eyes.
  
  
  METHODS
  A retrospective, non-comparative, interventional case series was conducted on 28 eyes of 26 patients who had two-stage laser in situ keratomileusis (LASIK) after penetrating keratoplasty. Records were reviewed with respect to the hinged lamellar keratotomy component of the procedure. The interval between keratoplasty and keratotomy was at least 1 year, and the follow-up period averaged 29 +/- 10 days. The Automated Corneal Shaper with nasal hinge was used. In addition to basic empirical astigmatism calculations, the Alpins method of astigmatism analysis was also employed to ensure that the influence of changes in cylinder axis were correctly taken into account when calculating the refractive change.
  
  
  RESULTS
  Surgically induced astigmatism from hinged lamellar keratotomy was not statistically significant in this series; however, the range in values (-9.06 to +7.57 D) has potential clinical ramifications. Nearly 70% of cases studied experienced surgically induced astigmatism of at least 2 D. Mean preoperative uncorrected vision was logMAR 1.06 +/- 0.41, which improved marginally postoperatively to logMAR 1.03 +/- 0.44 (P = 0.36). Best spectacle-corrected visual acuity averaged logMAR 0.21 +/- 0.16 preoperatively, improving to logMAR 0.09 +/- 0.15 (range -0.18 to 0.42) postoperatively, which was a statistically significant improvement (P < 0.01). No difference in refractive or visual outcomes was identified when those with keratoconus were compared to those with other underlying corneal disease processes.
  
  
  CONCLUSIONS
  Although mean surgically induced astigmatism was not statistically significant, hinged lamellar keratotomy caused considerable changes in astigmatism in nearly 70% of post-keratoplasty eyes studied. This suggests that clinically significant inaccuracies may result if a one-stage LASIK procedure is performed on such patients. The authors suggest that reassessment of refraction after keratotomy may improve refractive outcomes.
authors.affiliation: Ophthalmology Department, Cairns Base Hospital, Cairns, Queensland, Australia. nathanwalker@ausdoctors.net
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Walker
authors.forename: Andrew J G
authors.initials: AJ
authors.lastname: Apel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000503:physiopathology*; D003316:Corneal Diseases / Q000601:surgery*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D015948:Keratoplasty, Penetrating; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012189:Retrospective Studies; D014785:Vision, Ocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology