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David A Mackey, Seyhan Yazar, Hugh R Taylor, Paul Mitchell, Michael Hunter, Alex W Hewitt; Change of Refractive Error and Myopia in Australia over a Generation.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):905. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Emerging evidence from East Asian countries points to a dramatic increase in prevalence of myopia in recent decades. We performed a retrospective observational study to investigate whether the range of refractive error and prevalence of myopia may have changed in Australia.
We obtained refractive data from three population based studies. Two studies collected in the early 1990s, the Blue Mountains Eye Study (BMES) and Melbourne Visual Impairment Project (MVIP) were compared with the recent Busselton Healthy Aging Study (BHAS). Only participants aged between 49 and 64 years and whose refractive error was measured with an autorefractor were included in this analysis. Myopia prevalence was evaluated using spherical equivalent cut-off points of ≤-0.50D.
Refractive error was not normally distributed in the three studies. While the distribution was most kurtotic (6.40) in the BMES, it had a negative skew (-0.90) in the MVIP. There was a directional difference in refractive error distribution of the BMES and BHAS (Figure 1). The mean refractive error (95% confidence interval) was -0.08 D (-0.15 to 0.01) in the BMES and +0.49 D (+0.42 to +0.56) in the BHAS (t-test=11.72, p<0.001). The prevalence of myopia (≤-0.50D) was lower in BHAS (15.7%) compared to BMES (24.0%) and MVIP (26.5%) (F-statistic = 30.58, p<0.001).
There is no evidence of a major increase in myopia rates in the recent (BHAS) population. The directional difference observed between Blue Mountains and Busselton studies is similar to a shift in selection against an extreme and therefore may suggest an environmental variation between these two populations. The lower rate of myopia identified in BHAS also supports this finding. Busselton and the Blue Mountains are at similar latitudes. Future research investigating the particular lifestyle choices may help us to identify the modifiable risk factors in development and progression of myopia.
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