Eyeglass Lens Materials
There are 5 main materials that eyeglass lenses are created from:
Plastic lenses (also known as CR-39 lenses) are the most basic type of optical lens available. They are relatively lightweight, but are not very scratch resistant and are not shatter resistant. CR-39 plastic and glass are the only commonly used lens materials that do not protect 100% against UV rays.
They are a good lens choice for the budget-conscious individual, but are not the best option for someone who tends to be active, hard on their glasses, or needs the lenses to be shatter-resistant for sports. Because of these factors, we also do not recommend them for children.
Formerly the go-to lens option for individuals wanting a thin, lightweight, scratch-resistant lens option, polycarbonate is still a widely prescribed lens. It is a great option for children, as it is relatively inexpensive, and yet protects their eyes. Polycarbonate is very shatter-resistant, and also offers full UVA and UVB protection.
The major downside of polycarbonate lenses is that, because of their "ABBE value" (basically, the way the material bends or distorts light as it passes through), they can give some sensitive wearers a certain amount of peripheral distortion, especially those with higher prescriptions.
Trivex is one of the newest lens materials on the market. It has optical qualities that are more similar to basic plastic lenses, but also has the durability and thinness aspects of a polycarbonate lens. It is the lightest-weight lens material commonly available for eyewear use, although it is not necessarily the thinnest.
It is ideal for semi-rimless and drill-mount frames, as it does tend to chip or acquire stress cracks from regular use. It also tints much better than polycarbonate.
For active people, children and teenagers, people who are hard on their glasses, and people with mid- to moderate prescriptions, Trivex is hard to beat!
High-index lenses are generally the thinnest lens option available for high prescriptions (but, believe it or not, they may not be the thinnest option for an individual with a more mild prescription! Ask your optician for advice tailored to your prescription). Because of their density, however, they may not be the lightest-weight option. They do have a higher level of "chromatic aberration" (the tendency of the lens to slow down light enough that very sensitive wearers might see small "halos" or "rainbows" around lighter colored objects) than other plastic materials, but most patients with very high prescriptions find that the thinness of the lens more than compensates for the slightly distorted peripheral vision.
It is very important to have an anti-reflective coating on high-index lenses, as they tend to reflect a lot of light inside the lens itself (basically, the light passes through one side of the lens, and then tends to bounce around inside the lens a few times before it exits the lens, which creates lots of annoying "glints" that can be distracting, in addition to potentially contributing to more eye strain and fatigue).
Glass lenses, while the heaviest (approximately 2x as heavy as the equivalent lens in CR-39 plastic), are also the most scratch resistant. And while they are not as safe for high-impact activities, they do perform better for activities like soldering, since the material doesn't melt. They also tend not to react to the kinds of chemicals that could distress a plastic lens, like aerosols, ammonia, and other chemicals.
Because glass lenses can be extremely dangerous when they shatter, we highly advise that they not be selected for children, individuals who wear them while engaging in potentially dangerous-for-lenses activities (like sports, riding bikes, etc.), or people with clear vision out of only one eye.