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They are made with break-proof plastic lenses to protect the eye from flying debris or other matter. [4] ... which cost an average of $25–$50 U.S. to make, to an ...
The template for rimless eyeglasses date back to the 1820s, when an Austrian inventor named Johann Friedrich Voigtländer [] marketed a rimless monocle. [2] The design as it is known today arose in the 1880s [3] as a means to alleviate the combined weight of metal frames with heavy glass lenses.
Polycarbonate is commonly used in eye protection, as well as in other projectile-resistant viewing and lighting applications that would normally indicate the use of glass, but require much higher impact-resistance. Polycarbonate lenses also protect the eye from UV light.
Plastic lenses are lighter and shatter-resistant, but are more prone to scratching. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation.
Polycarbonate ( V d = 30–32 ) is very dispersive but has excellent shatter resistance. Trivex ( V d = 43 @ 1.53 ), is also heavily marketed as an impact-resistant alternative to Polycarbonate, for individuals who do not need polycarbonate's index. Trivex is also one of the lightest materials available.
Freeform designs are tailored to each prescription and do not have this problem. [5] Since the 1980s, manufacturers have been able to minimize unwanted aberrations by: improvements in mathematical modeling of surfaces, allowing greater design control; extensive wearer trials; and; improved lens manufacturing and measurement technology.
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