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M.A. Bullimore, G.L. Mitchell, K.S. Reuter, L.A. Jones, J. Zoz, M.J. Rah; The Influence of Age of Onset and Parental History on the Level of Myopia in an Adult Cohort . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5457.
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The Study of Progression of Adult Nearsightedness (SPAN) is a five–year observational study to determine the risk factors associated with adult myopia progression. Here we report the influence of age of myopia onset and family history on level of myopia at baseline.
Subjects between 25 and 35 years of age, with between –0.50 and –7.00 D of myopia (by cycloplegic auto–refraction) were recruited from the faculty and staff of The Ohio State University. A survey instrument was used to collect subject–reported data on age, gender, level of education, race, age at which spectacle wear began (a surrogate for age of onset of myopia), parental and sibling history of myopia, age of onset of myopia, family history of myopia, occupation, and history of contact lens wear. The factors affecting baseline myopia were examined using both univariate and multivariate analysis.
Three–hundred ninety–six subjects were enrolled in SPAN. The mean (± SD) age at baseline was 30.7 ± 3.5 years, the mean level of myopia (spherical equivalent) was –3.54 ± 1.77 D, and the mean age of myopia onset was 13.8 ± 5.5 years. Univariate analysis revealed that the level of myopia at baseline was associated with the age of myopia onset (r = 0.509, p < 0.001). Early–onset (prior to 15 years) myopes were more myopic than late–onset myopes. Baseline myopia was associated with the number of myopic parents (F = 4.16, p = 0.016) with subjects reporting two myopic parents more myopic than those reporting no myopic parents (–3.83 vs. –3.10 D, p = 0.013). Furthermore, subjects reporting a myopic mother were more myopic than those reporting a non–myopic mother (–3.79 vs. –3.28 D, F = 6.90, p = 0.009), but the reported refractive status of the subject’s father had no significant effect (F = 2.92, p = 0.089). There was no significant effect of sibling myopia on refractive error. Number of myopic parents was significantly related to age of onset (F = 8.57, p < 0.001). Of the early–onset myopes, 40% reported two myopic parents, but only 27% of late–onset myopes reported two myopic parents. Multivariate analysis incorporating both age of myopia onset and number of myopic parents, showed that age of onset was still significant (p < 0.001), but parental myopia was not (p = 0.52).
Both age of onset and number of myopic parents affect the level of myopia in a cohort of myopic subjects. Further analysis suggests, however, that the number of myopic parents affects the age of myopia onset and that any impact of parental refractive error on the level of myopia in our cohort is mediated by the age of onset of myopia.
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