All About Different Eyeglass Lens Materials

When you're buying a new pair of eyeglasses, there are a number of choices you have to make. Some of them are fun: what the frames will look like, what color they’ll be, what style you’ll get. Some choices, however, require a little more understanding of what you're getting yourself into. Specifically, what do you want your eyeglasses made out of? There are five standard eyeglass lens materials these days: polycarbonate, CR-39 (aka normal plastic), mid-index plastic (1.56), high-index plastic (1.6, 1.67, 1.7), and glass.

Glass lenses used to be the norm in eyewear lens materials—hence the name “eyeglasses.” Glass, however, is outdated, and its safety and durability limitations make it a last-choice nowadays. It is more prone to potentially-dangerous breakage, unlike polycarbonate and plastic. It is also more expensive than newer materials.

In a nutshell, the major difference between polycarbonate and plastic lenses is that polycarbonate is more impact resistant and lightweight, while plastic is more scratch-resistant and offers more options for tinting.

Polycarbonate lenses are extremely durable—as proved by the fact that polycarbonate is also the material used for bulletproof vests and space shuttle windows. Polycarbonate is the best choice in environments like construction, sports, or warehouses, where your glasses run a risk of being broken. But even if you don't spend time in such an environment, polycarbonate lenses are great for everyday use. Many have built-in UV protection and stop 99.9% of harmful rays from the sun, fluorescent lights, and computer screens.

Polycarbonate lenses by themselves, however, are scratch prone, much more so than CR-39. They are also a little more difficult to clean. Because of this, almost all manufacturers of polycarbonate automatically give it a scratch-resistant coating, eliminating scratching concerns. Polycarbonate is the second-most widely-used lens material in the United States, after CR-39.

CR-39 (normal plastic) is the most widely-used lens material. If you're looking for a specific color of tint to your prescription lenses, plastic is preferrable. CR-39 is more solvent-resistant and scratch-resistant than polycarbonate, which means that you can clean the lenses more easily. On the other hand, CR-39 does weigh more than polycarbonate, and will feel slightly bulkier on your face.

This is why mid-index (1.56) and high-index plastic (1.6, 1.67, 1.7) lenses exist. These lenses allow for tinting while mitigating the bulkiness of CR-39. The higher the index number, the thinner (and generally more expensive) the lenses. Cost usually increases with the index.

High-index lenses have the added detriment of sometimes not being available for people with high prescriptions, as an ultra-thin lens may not support a stronger prescription. Still, it is often far more stylish and attractive to have super-thin glasses, and the super-thin plastic lenses can, like CR-39 and mid-index lenses, be tinted however you like.

It's always a good idea to talk to your eye doctor. He or she will tell you what you should and shouldn't use, depending on your unique condition and the strength of your prescription.

Was this article helpful? Know someone who would be interested?