title: White-to-white corneal diameter: normal values in healthy Iranian population obtained with the Orbscan II.
abstract: OBJECTIVE
  To determine the normative values of white-to-white corneal diameter with Orbscan II Topography System and to compare right and left eyes data in the normal young population.
  
  
  METHODS
  A total of 1001 healthy participants aged 18-45y participated in this observational cross-sectional study. The study population consisted of 616 female and 385 male subjects. The corneal diameter was measured with the Orbscan II. The differences between genders, between right and left eyes and age-related changes were evaluated. Statistical analyses were performed using Student's t-test.
  
  
  RESULTS
  The average white-to-white distance in our study population was recorded as 11.65±0.36 mm (median: 11.60 mm, mode: 11.70 mm, minimum: 10.50 mm and maximum: 13.60 mm). The white-to-white distance was 11.60±0.35 mm in males and 11.71±0.36 mm in females which was statistically different between genders (P<0.01). However, white-to-white distance was not statistically different between right and left eyes. In addition, this parameter decreased with increasing age. Considering 95% confidence interval, corneal diameter less than 10.93 mm and greater than 12.34 mm would be considered as microcornea and megalocornea, respectively based on this study population, using the Orbscan II topography.
  
  
  CONCLUSIONS
  Detailed description and analysis of corneal diameter with Orbscan demonstrate that the obtained average value of horizontal white-to-white is higher in male than female and decreases slightly with increasing age. Our data also suggests the cut off values for definition of microcornea and megalocornea, which can be employed with this population.
authors.affiliation: Cornea Research Center, Mashhad University of Medical Sciences, Mashhad 9195965919, Iran ; Eye Research Center, Mashhad University of Medical Sciences, Mashhad 9195965919, Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Gharaee
authors.affiliation: Eye Research Center, Mashhad University of Medical Sciences, Mashhad 9195965919, Iran ; Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran 1336616351, Iran.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Abrishami
authors.affiliation: Eye Research Center, Mashhad University of Medical Sciences, Mashhad 9195965919, Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Shafiee
authors.affiliation: Refractive Errors Research Centre, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad 9176699186, Iran ; Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad 9176699186, Iran.
authors.forename: Asieh
authors.initials: A
authors.lastname: Ehsaei
keywords: Orbscan II; corneal diameter; normal population; white-to-white