Description
This article is from the Vision and Eye
Care FAQ, by grants@research.canon.com.au (Grant Sayer) with
numerous contributions by others.
2.4 Eyeglass Lens materials
Spectacle lenses are made of two main types of materials - plastic or glass.
Plastic lenses are often CR39 or polycarbonate. Glass lenses come in a
variety of refractive indexes, designed to minimise the thickness.
HiIndex lens materials are commonly 1.56, 1.60 and 1.67, as compared to
XXXX for common crown glass.
Ultimately, the lens choice is very much a user application. Hi Index
will provide a thinner edge and better cosmetic appearance but still
weigh in heavy. Comparatively, plastic lenses are lighter but in
high minus prescriptions will have a significantly thicker lens edge.
Furthermore the size of the frame will influence the overall edge thickness
since a larger eyesize means a larger lens.
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health, vision, eye care, contact lenses, spectacles, eyecare, prescriptions, sunglasses, surgery
