ABSTRACT
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. 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[degree sign], ATR astigmatism was defined as 90 +/- 19[degree sign], and oblique when the axes were 20-70[degree sign] and 110-160[degree sign]. The familial aggregation was investigated with a conditional model [quadratic exponential] and marginal model [alternating logistic regression] after controlling for confounders. 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]. 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