title: Corneal elevation and keratoconus indices in a 40- to 64-year-old population, Shahroud Eye Study.
abstract: OBJECTIVE
  To determine the corneal elevation values and keratoconus indices in the 40- to 64-year-old population and their changes with aging.
  
  
  METHODS
  The 6311 invitees of this study were selected through random cluster sampling, and 5190 of them participated in the study (response rate = 82.2%). Here, we analyzed results of Pentacam acquisitions in 4148 respondents. Cases of keratoconus and forme fruste keratoconus (FFKC) were determined using topography and clinical data. Studied variables included keratoconus indices, central corneal thickness readings, maximum elevations on the anterior and posterior surfaces, and elevation values at the thinnest point, anterior steepest point, and posterior steepest point in healthy, FFKC, and keratoconus groups.
  
  
  RESULTS
  In all subjects, the mean maximum elevations were 6.80 ± 5.0 μm and 16.60 ± 7.7 μm on the anterior and posterior corneal surfaces, respectively. Maximum elevation values on the anterior and posterior corneal surfaces showed significant correlations in the keratoconus, FFKC, and healthy groups (P < 0.002). Maximum anterior elevation correlated with age (r = 0.11, P < 0.001), but maximum posterior elevation showed no such correlation (P = 0.476). Keratoconus indices demonstrated significant changes with age (P < 0.001).
  
  
  CONCLUSIONS
  Anterior elevation values slightly increase with age, and keratoconus indices change as well. Elevation readings and keratoconus indices in the keratoconus group and FFKC cases are higher than the healthy corneas although their values could be compared with other studies on younger participants.
authors.affiliation: Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.affiliation: Lorestan University of Medical Sciences, Khorramabad, 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: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
authors.affiliation: Center for Health Related Social and Behavioral Sciences Research, Shahroud University of Medical Sciences, Shahroud, Iran.
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Emamian
authors.affiliation: Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Abbasali
authors.initials: A
authors.lastname: Yekta
authors.affiliation: Department of Community Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shariati
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Postal Box: 14155-6446, Tehran, Iran.
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
keywords: Corneal elevation; Pentacam; adult; cross-sectional study; keratoconus