title: Corneal topography patterns in the Tehran eye study: warning about the high prevalence of patterns with a skewed radial axis.
abstract: OBJECTIVE
  The purpose of this study is to determine the distribution of corneal topography patterns in Tehran.
  
  
  METHODS
  In this population-based study, a total of 442 individuals were randomly selected by cluster sampling for complete ophthalmologic examination. A total of 404 (788 eyes) met the inclusion criteria and were enrolled in this study. Orbscan II (Bausch and Lomb Surgical, Salt Lake City, USA) was used to determine the anterior segment indices and axial power maps for each eye.
  
  
  RESULTS
  On the basis of the axial power maps, the symmetric bowtie (SB) (29.0%) and asymmetric bowtie with inferior steepening (16.7%) patterns were the most prevalent and the irregular (3.3%) and superior steepening (1.5%) patterns the least prevalent. Asymmetric bowtie pattern with a skewed radial axis (AB-SRAX) was seen in 7.6% of eyes. These cases had both thinner and steeper corneas compared with round and SB ones (P < 0.014 and P < 0.006). Maximum anterior elevation in 5 mm zone, of AB-SRAX corneas were higher than other patterns (P < 0.01) except for superior steepened and inferior steepened ones.
  
  
  CONCLUSIONS
  The distribution of corneal topographic patterns in Iranians seems like other Asian population on the whole. The 7.6% prevalence of AB-SRAX patterns may be a warning on keratoconus prevalence in our population. This is in line with recent regional reports.
authors.affiliation: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran ; Farabi Eye Hospital, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.affiliation: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Asghar
authors.initials: A
authors.lastname: Beiranvand
authors.affiliation: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography / Q000145:classification; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D007640:Keratoconus / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D055815:Young Adult
keywords: Corneal Topography Pattern; Cross-sectional Study; Orbscan II; Tehran