Contact lens standards.
The British Standards Institution (BSI) is in the process of publishing an extensive series of standards relating to contact lenses which were originally formulated as International and European Standards. Standards specifying tolerance limits for the manufacture of rigid and hydrogel lenses have been based upon data on reproducibility derived from 'ring tests' in which measurements are made by a series of independent operators. Despite publication of an International Standard on terminology in 1986, some authors persist in using obsolete terms and this practice is deplored.
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