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dioptre |
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dioptreOptical unit in which the power of a lens is expressed as the reciprocal of its focal length in metres. The usual convention is that convergent lenses are positive and divergent lenses negative. Short-sighted people need lenses of power about −0.7 dioptre; a typical value for long sight is about +1.5 dioptre. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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The implants are scleral constrictor bands, segments or ribs for inducing accommodation of a few diopters, to correct refractive errors. The lens can treat nearsightedness between the ranges of -4 to -20 diopters with up to 3 diopters of astigmatism. The Food and Drug Administration warned that the implants are only for mildly nearsighted people, whose vision is formally diagnosed as ``minus 1 diopters to minus 3 diopters. |
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