This article is from the Vision and Eye Care FAQ, by grants@research.canon.com.au (Grant Sayer) with numerous contributions by others.
Since edge thickness is a function of lens power, centre thickness and
curvature of the front and back curves (all inter-related) the
edge thickness is influenced by the following features:
+ refractive index of the lens material
+ centre thickness (eg safety lenses have a greater central
thickness)
+ size of the spectacle frame, i.e larger eyesize means a
bigger lens.
 
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