title: Corneal refractive power and eccentricity in the 40- to 64-year-old population of Shahroud, Iran.
abstract: OBJECTIVE
  To determine the normal corneal curvature, power, and eccentricity in an Iranian population and their determinants.
  
  
  METHODS
  This report is part of a population-based study conducted in 2009. Of the 5190 participants of the study, Pentacam data from 8532 eyes of 4266 people who met the inclusion criteria for this analysis were used. For each eye, we extracted minimum and maximum keratometry readings, the average of the 2 readings (mean-K), the difference between these 2 parameters (keratometric astigmatism), and corneal eccentricity.
  
  
  RESULTS
  The average mean-K, keratometric astigmatism, and eccentricity were 43.73 ± 2.47, 0.90 ± 0.93, and 0.27 ± 0.63 diopter, respectively. Mean-K was directly correlated with age; inversely correlated with body mass index, axial length, white-to-white corneal diameter, and anterior chamber depth; increased at higher amounts of myopia; and was higher in women compared with men. Keratometric astigmatism was significantly higher in women, increased at higher amount of refractive error, but showed no association with other variables. Eccentricity was correlated indirectly with age and white-to-white corneal diameter, and directly with axial length. It increased with myopia.
  
  
  CONCLUSIONS
  Compared with other studies, the mean corneal power and eccentricity values were lower in this Iranian population sample. Our findings may have implications for clinical interventions, especially refractive surgery. Further studies can identify the causes of such differences in the shape and size of the cornea, which may also be attributable to the choice of the measuring device.
authors.affiliation: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Soheila
authors.initials: S
authors.lastname: Asgari
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Emamian
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Jafarzadehpur
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shariati
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology*; D058452:Axial Length, Eye / Q000033:anatomy & histology; D015992:Body Mass Index; D003315:Cornea / Q000033:anatomy & histology* / Q000502:physiology*; D063171:Corneal Pachymetry; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D007492:Iran; D008297:Male; D008875:Middle Aged; D044382:Population Groups; D012016:Reference Values; D012029:Refraction, Ocular / Q000502:physiology*; D014065:Tonometry, Ocular