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Frank M Jakobs, Diana Hering, Joerg Frischmuth, Frank Weber; The Association between Ametropia and Astigmatism in a Large-Scale Non-Clinical Population of German Military Recruits. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5850. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
It has been suggested in previous studies that astigmatism might be associated with higher degrees of ametropia. The purpose of this study was to investigate possible associations between myopia or hyperopia and different forms of astigmatism in man.
Medical records of 106,575 German military recruits, all male and all born in the same year, were retrospectively scanned for spherical and cylindric refractive error. Mean age at time of examination was 19.7±0.6 yrs. In this data set, no pupil dilatation or cycloplegia was performed. Myopia, hyperopia, and astigmatism were uniformly defined to be relevant from 0.5 D of spherical and cylindric power, respectively. Astigmatism was defined with-the-rule (WTR) when steep axis was 0±15°, against-the-rule when steep axis was 90±15°, and oblique astigmatism in the remaining cases.
21.8% of recruits were found to be myopic, 4.5% hyperopic, and 21.7% astigmatic, with an anisometropia rate of 0.7%. Single eye calculation of linear regression revealed a strong association between astigmatism and myopia R^2=0.903), as well as between astigmatism and hyperopia (R^2=0.905), with hyperopic astigmatism continuously outranging myopic astigmatism with ≥0.75 D. Substratification showed that the effect was primarily introduced by WTR astigmatism (p<0.04), while no statistical difference was seen in the variance of remaining groups (p<0.001). Emmetropia was associated with the lowest rates of astigmatism.
Our results suggest a role of ametropia in the genesis of astigmatism. Although in this study, hyperopia rates might have been underestimated due to missing cycloplegia, statistical power was sufficient to elaborate a distinct association between higjher ametropia and increasing astigmatism, with hyperopia being the stronger determinant and hyperopic astigmatism with-the-rule being the primary outcome, or vice versa. Further studies are needed in order to assess causality.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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