title: A comparative study on the effect of radial keratotomy in patients who live at sea level and high altitude.
abstract: OBJECTIVE
  To compare the refractive and keratometric results of matched pairs of patients who underwent radial keratotomy (RK) at sea level and high altitude.
  
  
  METHODS
  The results of 30 eyes that underwent RK procedures in two clinical centres at different altitude were analysed. One centre was at sea level (Istanbul) and the other at an altitude of 1720 m (Van). The patients in the two centres were matched regarding gender, age, degree of myopia, number of incisions and optic zone size. There were 15 eyes in each group. All operations were performed with a diamond blade using a Russian technique by the same surgeon.
  
  
  RESULTS
  The mean pre-operative spherical equivalent cycloplegic refractions (SECR) were -6.33 +/- 1.15 D and -6.32 +/- 1.01 D in the Istanbul and Van groups, respectively (p = 0.96). The mean post-operative SECRs were -1.93 +/- 1.03 D and -0.28 +/- 0.57 D in the Istanbul and Van groups, respectively (p < 0.001). The mean SECR changes were 4.40 +/- 0.92 D and 6.03 +/- 1.13 D in subjects who had undergone RK at sea level and at 1720 m, respectively (p < 0.001).
  
  
  CONCLUSIONS
  These results show that a higher myopic correction can be provided in patients who undergo RK at high altitude compared with those operated on at sea level. The RK nomograms used by refractive surgeons performing RK surgery at high altitude may need to be redesigned in the light of future studies with long-term follow-up.
authors.affiliation: Yüzüncü Yil University, Medical Faculty, Department of Ophthalmology, Van, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Cinal
authors.forename: T
authors.initials: T
authors.lastname: Yaşar
authors.forename: A
authors.initials: A
authors.lastname: Demirok
authors.forename: S
authors.initials: S
authors.lastname: Simşek
authors.forename: O F
authors.initials: OF
authors.lastname: Yilmaz
mesh_terms: D000328:Adult; D000531:Altitude; D003315:Cornea / Q000473:pathology; D005260:Female; D006801:Humans; D007646:Keratotomy, Radial; D008297:Male; D016555:Matched-Pair Analysis; D009216:Myopia / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D012029:Refraction, Ocular; D012189:Retrospective Studies; D016896:Treatment Outcome