How user-friendly and how accurate are these new devices? This article study tries to answer these questions. Recently, however, several other companies have introduced videobased centration systems capable of measuring pupillary distance and all other relevant centration parameters. In a paper published in 1997, Wesemann et al presented information on the accuracy of measurement obtainable with a PD-ruler, pupillometer and the only video centration device which was commercially available at that time. Without precise knowledge of these parameters, it is not possible to compute personalised progressive lenses. Additional fitting parameters such as back vertex distance, frame wrap angle and pantoscopic angle, need to be determined and specified for the lens order. Pupillary distance measurement alone is no longer sufficient. Due to the increasing success of so-called ‘personalised progressive addition lenses’, accurate lens centration continues to gain in importance. Centration errors may cause asthenopic problems, degrade the quality of stereoscopic vision and reduce the usable zones of progressive addition lenses. For a pair of spectacles, the lens power and centration need to be correct. Comparison of PD measuring devices Part 1 Dr Wolfgang Wesemann investigates the accuracy of measurement and usage characteristics of four video centration devices and four pupillometers in a comparative study Eye care practitioners’ main activities include eye refraction and subsequent selection, mounting and dispensing of spectacles.
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