Background/aims: To determine the potential influence of genetic factors on the prevalence of myopia in Tehran.
Methods: Of 6497 citizens of Tehran sampled from 160 clusters using stratified, random cluster sampling, 4565 (70.3%) participated in the study and were referred to a clinic for an extensive eye examination and interview. These were from 1259 nuclear families with the average size of 3.6. Refraction data obtained from 3321 participants aged sixteen years and over are presented. Three definitions of myopia as the spherical equivalent of -0.5, -1 and -2 diopters or less were used. Familial aggregation of myopia was evaluated with odds ratios and recurrence risk ratios (λR ) using a multiple logistic regression with generalized estimating equations (GEE) adjusted for age, sex, height and education.
Results: Multivariate analyses showed a strong familial aggregation of myopia among siblings, (λR ranging from 2.09 to 3.86) and parent-offspring pairs (λR ranging from 1.82 to 3.81) adjusted for age, sex, height and education. The aggregation increased with higher myopia thresholds and using cycloplegic refraction. The ORs for spouse pairs were not significantly different from 1.0. The association of myopia with sex, height, and education (and not age) remained significant in the final GEE2 model.
Conclusion: Findings indicate a relatively high degree of familial aggregation, independent of age, sex, height and education in Tehran's population. This residual aggregation may be due to heredity or the effect of unmeasured common environment.
- familial aggregation
- recurrence risk
- refractive errors