Many people believe that “glasses” are still made of glass, but in reality, most lenses are constructed of various types of plastic. Although glass is always an option, most people opt for plastic due to glass’ weight and potential to shatter. Below you’ll find a comparison of the various kinds of plastic options available on the market.
CR-39 plastic, also known as allyl diglycol carbonate (ADC), is the most basic kind of lens material. Typically, when your insurance says they “cover” the lenses, this is the material they mean. It is not shatter-resistant, nor is it UV-protective. Due to these limitations, we at Family Eye Care do not generally recommend this material for daily wear lenses. We want our patients to be safe, and wearing a shatter-resistant lens is much more reliable on a day to day basis.
Introduced in the 1980s, polycarbonate has been the gold-standard of lens materials ever since. It is both UV-protective and shatter-resistant, making it an excellent option for daily wear. It is frequently a “covered” lens material for children due to the shatter-resistance. Unfortunately, it isn’t the most optically clear material, which means the brain has to learn to tune out the distortion created by the material itself. Because of this, we tend to recommend other options that provide a more clear viewing experience.
Specifically designed to solve the clarity issue of polycarbonate lenses, trivex is the best of all worlds, currently. It offers shatter-resistance as well as UV-protection while providing a crystal-clear view. Even patients who are not sensitive to the distortion found in polycarbonate lenses find trivex to be an optimum lens.
The index of the lens describes the lens’ ability to refract light. The higher the index, the less material is needed to create a lens that will correct the patient’s vision. This translates to thinner and lighter lenses. If you have a higher prescription strength, you may want to consider high-index lenses to reduce the thickness and heaviness of your glasses.
While this may sound like an obvious choice for those with high prescriptions, high index lenses do have drawbacks. The most significant one is that they are not shatter-resistant. Especially for children, this factor should be weighed carefully since children are especially prone to breaking their glasses. Additionally, some patients experience visual distortion due to the way light travels through the lens. However, this can usually be mitigated with anti-reflective coating.
Lens Coatings and Treatments
In addition to many options for lens materials, you will also have several choices for lens coatings and treatments. At Family Eye Care, we will guide you through these options so you can rest assured you are making a well-informed choice that will maximize the visual quality of your lenses.
Anti-reflective coatings reduce the glare on your lenses. Glare is both fatiguing and can make nighttime driving difficult due to the glare of other vehicle’s headlights. The anti-reflective coating will help your eyes from becoming overly tired during the day and will also reduce the halo of oncoming lights at night. Additionally, they will reduce the glare on your lenses visible to others, so your glasses will appear more clear, and others will be able to see your eyes, rather than just your lenses. Anti-reflective coatings can be found on a wide array of lenses, such as on your camera, the screen of your smartphone, and the lenses inside the Hubble telescope.
We recommend the highest quality anti-reflective coatings to ensure their longevity. There are many different qualities of anti-reflective coatings on the market, and affect things such as durability, clean-ability, scratch resistance, and warranty.
Sun Reactive Lenses
When sun-reactive lenses are exposed to UV light, they turn from clear to dark. The most well-known brand is Transitions, and some people use this brand name interchangeably for all types of sun-reactive lenses, although it is important to note you have several other brand options as well. Sun-reactive lenses come with their own array of options, including colors, intensity of darkness, and even polarized or mirror effect when darkened.
Although they are similar to sunglasses in their ability to protect your eyes from UV rays, they are not a replacement for sunglasses necessarily. When behind the windows of your vehicle, for example, they will not react to the sunlight. They can be an excellent option though for those who find switching between their eyeglasses and sunglasses cumbersome, or who are light-sensitive.
Tinted vs. Polarized Lenses
When searching for sunglasses, one of the most common questions we get is, “What’s the difference between polarized and tinted lenses?” Tinted lenses have been darkened in a tint-bath. It can be done for numerous colors from dark grey to yellow to rose-colored. They can also be customized to different intensities, as well. It can be a solid, uniform intensity the entire length of the lens or can be a gradient from dark to light.
Polarized lenses, on the other hand, provide anti-glare functionality to sunglasses through the use of a special chemical that filters light. You may have noticed that tinted sunglasses do little more than darken what you’re looking at, while it remains difficult to see due to objects that are reflecting light. Polarization fixes this problem because the applied chemical molecules are lined up in such a way that they block some of the incoming light while allowing other light to pass through the vertical “openings.” This means that the light reflecting off shiny horizontal surfaces like bodies of water or car hoods, for example, is blocked.
Polarized sunglass lenses do have their limitations, however. They are not ideal when viewing LCD screens, such as those on televisions, vehicle dashboards, phones, or ATMs. Because light needs to penetrate the lenses both vertically and horizontally for LCD screens to be seen properly, polarized lenses will make it difficult to see what is on those screens.
BluTech Tinted Lenses
The blue light that comes from our many electronic devices is proving to be troublesome to both our health and comfort. Blue light also affects the brain’s ability to begin winding down to sleep, which is why looking at screens in the time before bed can be detrimental to falling asleep. BluTech lenses were developed to mitigate some of the adverse effects of blue light. These are not merely standard tinted lenses, but rather have a melanin injection into the lens material itself, thus filtering out as much as 40% of the blue light we see. This technology makes working on computers both safer and more comfortable for your eyes. Patients who have used BluTech say they feel less tired at the end of a long day of computer work and regularly recommend the lenses to their coworkers.
If you have questions about lens materials and coatings, please call Family Eye Care for an appointment today!