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This article is from the Vision and Eye Care FAQ, by grants@research.canon.com.au (Grant Sayer) with numerous contributions by others.

3.2.5 Bifocal Lenses

There are a variety of designs in bifocals, essentially all trying
to provide a transition or reading zone for use at near. The different
designs include;

+ aspheric multifocal -
+ simultaneous vision concentric - has either a central near or
distance zone with surrounding zone of opposite type to centre
(eg, centre near,distance surround)
+ diffraction/holographic - based on diffraction grating principles

 

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• prev: 3.2.4 Extended Wear
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