RESUMEN
Background: To determine the familial aggregation, Coaggregation and within person association of myopia and four phenotypes of astigmatism by a conditional model in Tehran Eye Study
Materials and Methods: Myopia, Total, ATR, WTR and oblique astigmatism were studied through a population based, cross sectional study in 1326 siblings older than 5 years from 531 families with 2-4 siblings using stratified cluster random sampling from August to December 2002 in Tehran Eye Study
Results: Based on the conditional model and via Proc GENMOD SAS 9.1, the conditional odds ratios [95% confidence interval], that indicates conditional familial aggregation, for the total, WTR, ATR and oblique astigmatism and myopia were 1.16 [1.01-1.33], 1.59 [1.17-2.16], 1.77 [1.39-2.26], 2.12 [1.41-3.19] and 1.96 [1.72-2.24], respectively .On the other hand, conditional odds ratios that indicates within person association of two disease, for myopia and WTR, myopia and ATR, myopia and Oblique and at last myopia and total astigmatism were 5.74 [3.99-8.17], 3.41 [2.01-5.82], 4.6 [2.15-9.86] and 6.10 [4.76-7.82], respectively. Although no significant familial co-aggregation has been identified
Conclusion: Based on conditional model and after controlling for the confounders, this analysis yielded, a significant aggregation of four phenotypes of astigmatism and myopia, a large within person association and moderate but non-significant coaggregation of these disorders