title: Analysis of familial aggregation in total, against-the-rule, with-the-rule, and oblique astigmatism by conditional and marginal models in the Tehran eye study.
abstract: OBJECTIVE
  The purpose was to determine the familial aggregation of the total, against-the-rule (ATR), with-the-rule (WTR), and oblique astigmatism by conditional and marginal models in the Tehran Eye Study.
  
  
  METHODS
  Total, ATR, WTR, and oblique astigmatism were studied in 3806 participants older than 5 years from August 2002 to December 2002 in the Tehran Eye Study. Astigmatism was defined as a cylinder worse than or equal to -0.5 D. WTR astigmatism was defined as 0 ± 19°, ATR astigmatism was defined as 90 ± 19°, and oblique when the axes were 20-70° and 110-160°. The familial aggregation was investigated with a conditional model (quadratic exponential) and marginal model (alternating logistic regression) after controlling for confounders.
  
  
  RESULTS
  Using the conditional model, the conditional familial aggregation odds ratios (OR) (95% confidence interval) for the total, WTR, ATRs, and oblique astigmatism were 1.49 (1.43-1.72), 1.91 (1.65-2.20), 2.00 (1.70-2.30), and 1.86 (1.37-2.54), respectively. In the marginal model, the marginal OR of the parent-offspring and sib-sib in the total astigmatism were 1.35 (1.13-1.63) and 1.54 (1.13-2.11), respectively; WTR 1.53 (1.06-2.20) and 1.94 (1.21-3.13) and; ATR 2.13 (1.01-4.50) and 2.23 (1.52-3.30). The model was statistically significant in sib-sib relationship only for oblique astigmatism with OR of 3.00 (1.25-7.20).
  
  
  CONCLUSIONS
  The results indicate familial aggregation of astigmatism in the population in Tehran adjusted for age, gender, cataract, duration of education, and body mass index, so that the addition of a new family member affected with astigmatism, as well as having a sibling or parents with astigmatism, significantly increases the odds of exposure to the disease for all four phenotypes. This aggregation can be due to genetic and/or environmental factors. Dividing astigmatism into three phenotypes increased the odds ratios.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Rakhshani
authors.forename: Kazem
authors.initials: K
authors.lastname: Mohammad
authors.forename: Hojjat
authors.initials: H
authors.lastname: Zeraati
authors.forename: Keramat
authors.initials: K
authors.lastname: Nourijelyani
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000453:epidemiology* / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D016017:Odds Ratio; D012029:Refraction, Ocular; D012189:Retrospective Studies; D017678:Sex Distribution; D055815:Young Adult