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Frank Schaeffel; The role of peripheral optics in the development and progression of myopia. Journal of Vision 2013;13(15):T23. doi: 10.1167/13.15.23.
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© ARVO (1962-2015); The Authors (2016-present)
After the discovery by Wallman and colleagues (1987) that eye growth is controlled in localretinal areas by features of the retinal image, it became clear that the peripheral optics cannotbe neglected when the development of myopia is to be explained. Myopic eyes have already amore prolate shape and have therefore more hyperopic refractions in the periphery, acondition, which may stimulate myopia development. Conventional spectacles typicallygenerate more hyperopic refractions in the periphery which may tell the retina that further eyegrowth is needed. In monkeys, it was found that defocus imposed in the periphery of the visualfield is sufficient to induce foveal refractive errors. Consequently, various types of opticalcorrections are developed to leave the peripheral retina more myopic in the hope that thiswould inhibit eye growth. The upper retina seems to be most responsive since progressiveaddition lenses and executive bifocal lenses are similarly effective as lenses with a radialrefraction gradient (RRG). One confusing observation is that the peripheral refractions inhuman subjects are very variable, even if they are emmetropic in the fovea. To imposeconsistent relative myopia in the periphery, individualized spectacle designs may be necessary.The variability also raises the question as to whether the peripheral visual field in primatesemmetropizes at all, or whether it only contributes to emmetropization in the fovea. Anotherinteresting question is why undercorrection of myopia does not work as RRG lenses, butaccommodation is likely to be different with RRG lenses and with undercorrection.
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