What Are Eyeglasses Made Of?
Posted on March 8, 2016
In our last publication, we discussed the process of purchasing prescription glasses and their respective lenses. Here, we look further into the manufacturing process and what eyeglasses are actually made of. Understanding the construction of eyeglasses helps most patients determine the best design and style for them. So without further adieu, let’s discuss some of the basic terms relating to the technical aspect of prescription glasses.
Index of Refraction
The index of refraction deals with a scale that relays a material’s ability to bend light coming through it. The higher the refractive index for a material, the slower light travels through it. When using a higher refraction index, you’re not required to use as much material. Although glass lenses may be more delicate and heavy, their high index allows manufacturers to build a thinner design with the same medical function.
The abbe value enables manufacturers the ability to measure of the optical quality of lens material. It objectively measures the width in which the material spreads different wavelengths of light that travel through it. Lenses with low Abbe values tend to disperse light wavelengths more widely, which can cause an optical error called chromatic aberration. When this occurs, patients often complain about visible halos of colors around objects. These halos are most visible when you look at the edges of the lenses rather than the central optical zone. Depending on the material used, Abbe values vary from the high 59 of crown glass to the low 30 of polycarbonate.
Lenses with an aspheric design are the complete opposite of most lens designs. Usually, most materials are formed by having the the curvature degree change from the center out to the edges. The purpose surrounds creating a thinner and lighter pair of glasses with better proportionality.
The design process of aspheric lenses also allows manufacturers to use flatter curves on the lenses without sacrificing the optical quality. Flattening the curves helps reduce the amount of unnecessary magnification of the lenses and is said to make you look more beautiful while improving the clarity of your peripheral vision.
Aspheric designs are most seen in high index plastic lenses in order to make the best out of the lenses’ appearance alongside optical performance. When incorporated with polycarbonate and CR-39 lenses, this design tends to be quite costly, but more effective.
Minimum center thickness
Also known as edge thickness, this important feature is affected by the impact resistance standard that’s established by FDA. Most of the time, patients prefer thin lenses are developed from high-index material with an aspheric design, but a strong prescription can alter your design. If you’re looking to avoid thick lenses, make sure you’re paying attention to the shape and size of your eyeglass frames. Another approach that addresses lense thickness includes selecting a well-centered, smaller fame in order to reduce the weight and solidity.
Putting everything together..
Now that you understand the types of materials and approaches used to make eyeglasses, it’s time to select the perfect pair! Before doing so, it’s also important to understand additional features that protect and extend the life of your lenses and frames. Certain situations that cause damage may not be covered by the insurance company, so it’s up to you to maintain your glasses. Below, are some comfort and durability features that come in the form of coatings..
- An Anti-scratch coating can save glass lenses with soft surfaces from being severely scratched. If you own a pair of lightweight lenses made from plastic/high-index plastic (except polycarbonate), you’re alreay in need of an anti-scratch coat. If you think you might struggle to avoid scratching your lenses, or if you’re buying glasses for kids, then ask for an anti-scratch warranty during purchase. It’s worth the additional investment.
- Anti-reflective coating serves multiple purposes when it comes to improving your glasses in terms of functionality and appearance. By eliminating reflection in glass lenses, this type of coating actually improves the contrast and clarity of your vision. This especially comes in handy by helping you avoid reflective distractions in order to make better eye contact with people.
Moreover, anti-reflective coating removes the glare from your eyes while taking photographs. If you use high-index glass lenses, then anti-reflective coating is very important, because higher refractive index means more light being reflected by the lenses.
- UV-blocking treatment is a useful addition to glass lenses that protects your eyes from the damaging effect of Ultraviolet (UV) rays. This type of treatment isn’t necessary for nearly all high-index plastic materials or lenses made from polycarbonate as they both naturally absorb UV rays. In addition, if your lenses are made from CR-39 plastic, then UV-blocking coating is a necessity.
- Photochromic treatment is another amazing addition to lenswear. This type of treatment allows your lenses to change from transparent to tinted color when exposed to sunlight. Once you return indoors, they rapidly return to their clear form. Photochromic lenses fit almost any frame or design and are perfect for people of all ages as they eliminate the need for a separate pair of sunglasses.
Our Durable Medical Equipment store offers a wide range of glasses with different types of lens coatings that fit with your specific needs. No matter if you’re looking for an exam, fitting, or new frame design, our home optics program comes to you! Feel free to reach out to our registration department for more information and receive proper assistance choosing and ordering the most effective pair of glasses for you.