Editing Corrective lens (section)

=== Optical plastics ===
Plastic lenses are currently the most commonly prescribed lens, owing to their relative safety, low cost, ease of production, and high optical quality. The main drawbacks of many types of plastic lenses are the ease by which a lens can be scratched, and the limitations and costs of producing higher-index lenses.

==== CR-39 ====
{{main|CR-39}}
* [[Refractive index]] ({{mvar|n}}{{sub|d}}): 1.498 (standard)
* [[Abbe number]] ({{mvar|V}}{{sub|d}}): 59.3
* [[Density]]: 1.31 g/cm³
* [[Cutoff (physics)|UV cutoff]]: 355&nbsp;nm

[[CR-39]] lenses are inherently scratch resistant.

==== Trivex ====
* [[Refractive index]] ({{mvar|n}}{{sub|d}}): 1.532
* [[Abbe number]] ({{mvar|V}}{{sub|d}}): 43–45 (depending on licensing manufacturer)
* [[Density]]: 1.1 g/cm³ (the lightest corrective lens material in common use)
* [[Cutoff (physics)|UV cutoff]]: 394&nbsp;nm

Trivex was invented by Edwin C. Slagel and patented in September 1998.<ref name="patent">
{{cite patent
 | country = US
 | number  = 6127505
 | status  = Expired
 | title   = Impact resistant polyurethane, and meteor of manufacture thereof
 | pubdate = 3 October 2000
 | gdate   = 3 October 2000
 | fdate   = 2 September 1998
 | pridate = 2 February 1995
 | inventor= Slagel, Edwin C.
 | assign1 = Simula, Inc.
 | url     = https://patentimages.storage.googleapis.com/da/bd/da/1ce12187652eef/US6127505.pdf
}}
</ref>

Trivex was developed in 2001 by [[PPG Industries]] for the military as transparent armor.<ref name=eyecarebusiness-2001>{{cite news |last=Bruneni |first=Joseph L. |date=1 September 2001 |title=Alternative lens material |website = Eyecare Business |url=http://www.eyecarebusiness.com/articleviewer.aspx?articleID=50369 }}</ref> With [[Hoya Corporation]] and Younger Optics, PPG announced the availability of Trivex for the optical industry in 2001.<ref name=eyecarebusiness-2001/> Trivex is a urethane-based pre-polymer.<ref name=patent/> PPG named the material Trivex because of its three main performance properties: Superior optics, ultra lightweight, and extreme strength.<ref name=eyecarebusiness-2001/>

Trivex is a relative newcomer that possesses the UV-blocking properties and shatter resistance of [[polycarbonate]] while at the same time offering far superior optical quality (i.e., higher Abbe number) and a slightly lower density. Its lower refractive index of {{nobr| {{mvar|n}}{{sub|d}} {{=}} 1.532 }} vs. polycarbonate's 1.586 may result in slightly thicker lenses depending upon the prescription. Along with polycarbonate and the various high-index plastics, Trivex is a lab favorite for use in rimless frames, owing to the ease with which it can be drilled and its resistance to cracking around the drill holes. One other advantage that Trivex has over polycarbonate is that it can be tinted.{{Citation needed|date = January 2015}}

==== Polycarbonate ====
* [[Refractive index]] ({{mvar|n}}{{sub|d}}): 1.586
* [[Abbe number]] ({{mvar|V}}{{sub|d}}): 30
* [[Density]]: 1.2 g/cm³
* [[Cutoff (physics)|UV cutoff]]: 385&nbsp;nm

Polycarbonate is lighter weight than normal plastic. It blocks UV rays, is shatter resistant, and is used in sports glasses and glasses for children and teenagers. Because polycarbonate is soft and will scratch easily, a scratch-resistant coating is typically applied after shaping and polishing the lens. Standard polycarbonate with an Abbe number of 30 is one of the worst materials optically if chromatic aberration intolerance is of concern. Along with Trivex and the high-index plastics, polycarbonate is an excellent choice for rimless eyeglasses. Similar to the high-index plastics, polycarbonate has a very low Abbe number, which may be bothersome to individuals sensitive to chromatic aberrations.

==== High-index plastics (thiourethanes) ====
* [[Refractive index]] ({{mvar|n}}{{sub|d}}): 1.600–1.740
* [[Abbe number]] ({{mvar|V}}{{sub|d}}): 42–32 (higher indexes generally result in lower Abbe numbers)
* [[Density]]: 1.3–1.5 (g/cm³)
* [[Cutoff (physics)|UV cutoff]]: 380–400&nbsp;nm

High-index plastics allow for thinner lenses. The lenses may not be lighter, however, due to the increase in density vs. mid- and normal index materials. A disadvantage is that high-index plastic lenses have a much higher level of [[chromatic aberration]]s, which can be seen from their lower [[Abbe number]]s. Aside from the thinness of the lens, another advantage of high-index plastics is their strength and shatter resistance, although not as shatter resistant as [[polycarbonate]]. This makes them particularly suitable for rimless eyeglasses.

These high-refractive-index plastics are typically thiourethanes, with the [[sulfur]] atoms in the polymer being responsible for the high refractive index.<ref name="mitsui-high-n"/> The sulfur content can be up to 60 percent by weight for a material with index {{nobr|{{mvar|n}}{{sub|d}} {{=}} 1.74 .}}<ref name="mitsui-high-n">[http://www.mitsuichem.com/special/mr/resources/img/MR_article_in_MAFO_magazine_2009.pdf Is the sky the limit?] MAFO Ophthalmic labs & Industry, April 2009</ref>