Dioptre
However most languages have borrowed the original name and some national standardization bodies like DIN specify a unit name (dioptrie, dioptria, etc.).The idea of numbering lenses based on the reciprocal of their focal length in metres was first suggested by Albrecht Nagel in 1866.Thus an eye care professional, having determined that a myopic (nearsighted) person requires a basic correction of, say, −2 dioptres to restore normal distance vision, might then make a further prescription of 'add 1' for reading, to make up for lack of accommodation (ability to alter focus).[6] In focusing, the ciliary muscle contracts to reduce the tension or stress transferred to the lens by the suspensory ligaments.Convex lenses have positive dioptric value and are generally used to correct hyperopia (farsightedness) or to allow people with presbyopia (the limited accommodation of advancing age) to read at close range.
Diopter (disambiguation)British spellingAmerican spellingunit of measurementdimensionreciprocal lengthreciprocal metreoptical powermirrorphysical quantityreciprocalfocal lengthmetresradii of curvaturevergenceoptical beamsthin lens formularelatively thin lensesmetric systeminternational system of unitsinverse metrevision careophthalmologistFerdinand MonoyerdioptriceJohannes Keplereye care professionalcorrective lensesprescriptionmyopicaccommodationcorneacrystalline lensciliary muscletensionstresssuspensory ligamentsamplitude of accommodationhyperopiapresbyopiaOver the counterreading glassesmyopiaOptometristsrefractive errorcurvatureradiuscircleindex of refractionradius of curvatureMagnificationmagnifying glassAstigmatismDioptricsLens clockLensmeterOpticsOptometryVertometerH. K. Lewis & Co. Ltd.Smith-Kettlewell InstituteAddison–Wesley