It’s a misconception that glasses lenses are made of glass. Fun fact! Even proto-sunglasses, that predate corrective lenses, weren’t made from glass, but a mineral called quartz instead. So, what are glasses lenses made of? Yes, originally most eyeglass lenses were made of glass. But as lens technology advanced, the lens material for eyewear shifted from glass to plastics. Now, lens makers use different types of high tech plastics for different lens indexes, hardnesses, and needs. So let’s take a look at the different types of plastics and materials used to make modern glasses lenses.
Plastic eyeglasses and sunglasses lenses
Whether for sun, fun, or daily use, most glasses are made with plastic lenses, or “organic glass” if you want to get fancy. So why are glasses lenses made of plastic? In most cases, they’re lighter than traditional glass lenses used in eyeglasses, which means they’re more comfortable to wear. It’s also easier to apply lens coatings like anti-glare to plastic lenses. And there’s a reason children’s cups are made of plastic: it’s more resistant to impact. There are four main types of plastics used to make eyeglass and sunglass lenses: plastic, Trivex, polycarbonate, and high-index plastics.
Warning: we apologize in advance if things get a little sciencey!
First up, we have basic plastic lenses which are made from CR-39, a plastic polymer. CR-39 is an abbreviation for “Columbia Resin #39”, the 39th plastic of that type made by Columbia Resin, the company that developed the polymer.
After that, we have polycarbonate glasses lenses. A synthetic plastic discovered in the 1890s, polycarbonates became out of this world once they found use in aeronautics. Polycarbonate is a type of plastic that can be produced as transparent and easily shaped, making it a great for optical (glasses) lenses. It’s also impact resistant, meaning they’re a good lens choice for kids (or adults!) who tend to be accident prone. Similar to polycarbonate, Trivex glasses lenses are made of impact resistant urethane based pre-polymer plastic. Aside from both being impact resistant, Trivex and polycarbonate lenses have 100% UV protection.
Finally, there’s high-index plastics. The plastics used for this type of lens often contain sulfur. The atoms of this odorous element help these lenses have a higher refractive index, meaning a thinner lens. Although high-index lenses may be thinner, they’re heavier due to the higher density of these plastics.
Symmetry, in Taupe
Glass eyeglasses lenses
If plastic lenses are the norm for glasses, then why do some people still use glass lenses? For starters, all lenses are best for certain uses. Even though lens technology has advanced to the point of being able to correct certain types of colorblindness, there is no one perfect corrective lens. One of the main advantages of glass lenses for prescription glasses or sunglasses is that glass has a better index range. This doesn’t matter to most people, especially for those who have little to no prescription. It does matter to glasses wearers with incredibly strong prescriptions. Lenses made from mineral glass means you can get thinner lenses with less distortion. Another advantage of glass lenses is that they are harder, meaning they’re more resistant to scratches. So why aren’t glasses lenses made of glass? The main reasons are that glass lenses are heavier, more delicate, and more difficult to produce. Glass eyeglass lenses are made from different types of glass, like borosilicate, depending on index and manufacturer.
What you need to know about glasses lenses
First of all, getting the right lens coatings can make a world of difference in your lenses, no matter what they’re made of. That’s why EyeBuyDirect offers a wide selection of coatings to help protect your eyes and your lenses. In fact, your lenses are so important to us that offer our scratch resistant coating for free! A quick side note: EBD does not carry, Trivex or glass lenses, but we do up to six different lens indexes you can shop from depending on your prescription. Want to know more about out lenses? Send us a Tweet so we can chat!