Index and materials

Specialist’s continuously research in physics combined with constant technologies evolution has led to a various number of index refraction available at this moment on the market that can meet every patient expectation.

Available organic materials are:

1.5 CR-39

In 1930, plastic was first introduced to the optical lens industry as a laminate glass lens for car windshields to prevent excessive splintering of glass in case of accident but short lived. This paved the way for the Igard lens, the first true plastic lens but unfortunately despite its lightweight it turned yellow, scratched easily and was expensive.

CR-39 abbreviations has its origin in ”Columbia Resin” 39th formula, a study of a thermosetting plastic developed by the Columbia Resins project in 1940. During World War II, CR-39 monomer was used to reduce weight and increase the range of the bomber by creating a glass-reinforced plastic fuel tank. A few years later after the war, in 1947 the Armorlite Lens Company in California was credited with manufacturing the first CR-39 eyeglasses lenses.

Today, CR-39 is a trademarked product of PPG Industries.

Due its lightweight in comparison with glass, high Abbe number 58 yields low chromatic aberration, high abrasion resistance and transparency in visible spectrum and almost completely opaque in the ultraviolet range, nowadays CR-39 is the most common material in producing optical lenses.

Other benefits are related to its stand up to heat and household chemicals and cleaning products, aging, and to material fatigue. CR-39 is not dedicated exclusively to eyeglasses, but also to sunglasses due the wide range of colors that can be achieved by dyeing of the surface or the bulk of the material.

1.53 Trivex

Trivex lens material was initially designed by PPG Industries in the United States for use by the military in helicopter windshields and fighter jet canopies. Then in 2002, PPG Industries fine tune this material chemistry in terms of lightweight’s comfort and impact-resistance for specifically use in optical industry.

Excellent optics, lightweight comfort and high strength are three keys performance properties that inspired material name “Trivex”.

Considering its exceptionally lightweight and impact-resistance quality, Trivex become quickly Polycarbonate competitor as both of these materials are equally designed for safety glasses, sport glasses and of course it is safe for people all ages, including children and seniors. Although these two materials have a lot in common, they differ in the way they are manufactured and other properties: Trivex lenses are cast molded while Polycarbonate lenses are injection molded, and the result is a sharper optics for Trivex according to PPG Industries.

Considering high Abbe number 45 material Trivex has, this will translate into less chromatic aberration and significant clearer vision than most lenses.

Trivex lenses are exceptionally comfortable to wear as they have the lightest specific gravity (density per unit volume) of any lightweight material and this reduces the risk of glasses sliding down the bridge of the nose.

Trivex material is impact-resistant, does not shatter on impact, rarely scratch and can tolerate extreme temperatures without cracking or warping. It also protects patient’s eyes blocking 100% of harmful rays without any special films or coatings.

1.56 Middle Index

This material is a polycarbonate composite made from polycarbonate, other polymers and resins to keep it thinner and lighter than standards 1.5 CR-39 lens. In comparison with standard 1.5 CR-39, 1.56 Middle Index reduces lens thickness by 15%, providing improved aesthetics and comfort.

1.56 lens combines great optics with a thin, lightweight design and offers 56% UV protection.

Eyewear professionals recommend 1.56 lens material for full-rim eyeglasses frames and glasses for people who enjoy an active lifestyle, and not for rimless frames.

1.59 Polycarbonate

Due its high versatility, Polycarbonate was originally designed as a material for aerospace gear in the Apollo Space Shuttle expedition and over time used for headlights, CDs and many other industrial needs.

This material was introduced in ophthalmic market in 1980s by Gentex Corporation; since then, it has become a very popular choice, especially in case of highly active people and kids due many advantages as impact-resistance, lightweight, comfortable design, versatility and UV protection.

Polycarbonate lenses are one of the most impact-resistance lenses on the market and they’re not likely to crack, chip or shatter if they’re dropped or hit with something. The manufacturing process of these lenses creates a solid yet thin product up to 30% in comparison with standard plastic or glass lenses; due this reason it can accommodate strong prescriptions and in same time making the lenses rest easily and comfortably to wearing all day long. Polycarbonate protects from hazardous UVA and UVB light rays and blocks 100% of UV that passes through it allowing the wearer to work efficiently near bright light sources. Because they have built-in UV protection, no additional treatment is need for this purpose.

Optical quality, low scratch resistance and cost are considered main disadvantages of this material. With only 30 Abbe value although it offers a crisp field of view, Polycarbonate lenses have a lower clarity than some other materials like Trivex, meaning they have the potential to cause slight chromatic aberrations (visual distortions) in peripheral vision. Despite its flexibility and highly impact-resistance, Polycarbonate scratches easily. Adding an anti-scratch coating combat low scratch resistance disadvantage but this generates expenses for the final wearer.

1.60, 1.67 and 1.74 High Index

In 1987, Optima Inc. launched HYPERINDEX® 1.60 as a response to shortcomings of available lens material existent on the market at that time: thickness and unsightly cosmetic or optics quality (in case of 1.59 polycarbonate lenses). This company managed to combine in one material three of sought-after eyeglasses lens benefits: lightweight, ultra-thin and visual distortion-free optics. Lenses produced with this material index, delivered an unprecedented level of optical clarity, it dramatically improved cosmetic appearance and eliminated many common complaints related to swim effect (associated with polycarbonate lenses), peripheral distortion, magnification and size-reduction of objects and eye.

A few years later, in 1992 same company Optima Inc. made a step further and introduced in the optical industry the innovative HYPERINDEX® 1.66 index refraction: a thinner and lighter material lens with a wider margin in comparison to all existent materials. In 2000, it was launched MR-1.74, a record-high refractive index that made possible producing thinner and higher-powered corrective lenses.

“High Index” term refers to the refractive index of a lens and it is related to a lens ability to bend light: the higher the refractive index is, the more efficient the lens is at bending light and correcting vision. High index lenses can accommodate strong prescription without adding unnecessary thickness.
High index lenses are thinner, lighter, versatile, fit most of the frames and they are comfortable.
Disadvantages of high index lenses are they are not as impact-resistance as other lenses, they can cost more and they are more reflective than other lenses, so an anti-reflective coating is a must.