title: Corneal resistance factor and corneal hysteresis in a 6- to 18-year-old population.
abstract: OBJECTIVE
  To determine the distribution and normal range of the corneal resistance factor (CRF) and corneal hysteresis (CH) in the 6- to 18-year age range and their relationship with biometric components.
  
  
  METHODS
  Dezful, Iran.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  This study of Dezful school children used a multistage, stratified, cluster approach sampling. All students had examinations for biometry, noncycloplegic refraction, and corneal biomechanical properties; the examinations were performed in the same order in all cases.
  
  
  RESULTS
  Of the 864 selected students, 683 participated in the study. The mean CRF and CH was 11.74 mm Hg±1.77 (SD) (95% confidence interval [CI], 11.58-11.89) and 11.49±1.91 mm Hg (95% CI, 11.33-11.65), respectively. In a linear multiple regression model, the CRF significantly correlated with female sex (β coefficient=0.488, P=.013), central corneal thickness (CCT) (β coefficient=.034, P=.001), and keratometry (β-coefficient=0.157, P=.003) and CH significantly correlated with CCT (β coefficient=0.025, P<.001), axial length (β coefficient=-0.303, P=.011), and keratometry (β coefficient=0.11, P=.043). Each year increase in age was associated with a 42-unit decrease in the peak 1 area (P=.003).
  
  
  CONCLUSIONS
  The distribution of CRF and CH in an Iranian population was symmetrical and bell shaped. However, the CRF did not have a normal distribution. The mean CRF and CH were higher than those reported in almost all previous studies.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran.
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Jafarzadehpur
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran.
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran.
authors.forename: Abbasali
authors.initials: A
authors.lastname: Yekta
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran.
authors.forename: Hadi
authors.initials: H
authors.lastname: Ostadimoghaddam
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Norouzirad
authors.affiliation: From the Noor Ophthalmology Research Center (Hashemi, Jafarzadehpur, Mehravaran), Noor Eye Hospital, and the Department of Optometry (Jafarzadehpur), Iran University of Medical Sciences, the Department of Epidemiology (Khabazkhoob) Faculty of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, the Refractive Errors Research Center (Yekta, Ostadimoghaddam) and the Department of Optometry (Yekta, Ostadimoghaddam), School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, and the Dezful University of Medical Sciences (Norouzirad), Dezful, Iran. Electronic address: khabazkhoob@yahoo.com.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
mesh_terms: D000293:Adolescent; D058452:Axial Length, Eye / Q000033:anatomy & histology; D001696:Biomechanical Phenomena / Q000502:physiology; D001699:Biometry; D002648:Child; D003315:Cornea / Q000502:physiology*; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D004547:Elastic Tissue / Q000502:physiology*; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D012016:Reference Values; D014792:Visual Acuity / Q000502:physiology