title: Age-Related Changes in Corneal Curvature and Shape: The Shahroud Eye Cohort Study.
abstract: OBJECTIVE
  To determine 5-year changes in corneal curvature and asphericity in a population-based cohort study of 40 to 64 year olds in Iran.
  
  
  METHODS
  This report is based on data from the first and second phases of the Shahroud Eye Cohort Study conducted in 2009 and 2014, respectively. In this report, Pentacam data from 3749 people were used. Extracted variables included the maximum and minimum simulated keratometry readings (Kmax and Kmin), the mean radius of sagittal curvature (MRSC) in the central 3- and 2-mm rings between 3 to 11 mm from the center, and the anterior and posterior asphericity in both study phases. In the analysis, repeated-measures analysis of variance was used with a significance level of 0.5.
  
  
  RESULTS
  During the 5-year period of this survey, Kmax and Kmin increased by 0.38 ± 1.95 diopters and 0.46 ± 1.97 diopters, respectively. According to the mean radius of sagittal curvature indices, the cornea steepened in the center up to the 5- to 7-mm ring and flattened in the periphery. The increase in anterior and posterior asphericity was 0.15 ± 0.14 and 0.09 ± 0.14, respectively (all P < 0.001). Women, compared to men, showed more change in Kmax, Kmin, and posterior asphericity (all P < 0.001), but not in anterior asphericity (P = 0.937).
  
  
  CONCLUSIONS
  In 40 to 64 year olds, changes are in line with maintaining a prolate ellipsoid shape of the cornea. The corneal surface undergoes greater changes in women than in men. The anterior surface changes more than the posterior.
authors: *Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran; †Department of Epidemiology, School of Public Health, Shahroud University of Medical Sciences, Shahroud, Iran; and ‡Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors: Hassan
authors: H
authors: Hashemi
authors: Soheila
authors: S
authors: Asgari
authors: Mohammad Hassan
authors: MH
authors: Emamian
authors: Shiva
authors: S
authors: Mehravaran
authors: Akbar
authors: A
authors: Fotouhi
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D015331:Cohort Studies; D003315:Cornea / Q000033:anatomy & histology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007492:Iran; D008297:Male; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology