Originally posted by oracleslave
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-6 is short for -6 diopters; this is the reciprocal of the focal length (of the corrective lens) in metres, meaning your optical system is at infinity at 17 cm from the eye. Before the age of 40 your lens can bring that focal point somewhat closer yet. Or in other words it's not so much that you have bad eyeisght, but have really good eyesight up close. Typically people end up needing +2D lenses or so as they age, though this would be more for longsighted people. Short sighted people can just take off their glasses for close work.
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