Editing Corrective lens (section)

==== 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>