RESUMO
PURPOSE: To investigate the impact of a positive family history of high myopia on the level and onset of myopia and its ocular components. METHODS: A cross-sectional study was conducted. The participants (aged 17 to 45 years) were categorized into four groups: normal, mild, moderate, and high myopia. The age of first glasses for myopia was used as the onset of myopia. The impact of the family history on the level and the onset of myopia was quantified. Parental effect on corneal curvature (CC), anterior chamber depth (ACD), and axial length (AXL) was analyzed. RESULTS: The study included 185 normal subjects, 170 mild, 140 moderate, and 392 high myopes. Family history was strongly associated with the probands' status (P < 6 x 10(-12)). When there was >or=1 highly myopic parent, the odds ratios (ORs) of developing mild or moderate myopia were between 2.5 and 3.7 (95% CI: 1.1-6.5) and the ORs of having high myopia were > 5.5 (95% CI: 3.2-12.6). A strong association (P = 2 x 10(-6)) between parental myopic state and the AXL in the subjects was also found, but there was no statistical relationship for ACD or CC. There was an association between high myopia in parents and the onset of myopia in children. Siblings had a weaker association with the level of myopia and had no effect on the onset of myopia. CONCLUSIONS: This study found strong familial effects on the level and onset of myopia even after adjusting for environmental factors. The parental effect on ocular components in their offspring was primarily on AXL.