Eyeglass Lenses

Get familiar with the materials that make up your eyeglass lenses. Use our guide to replace new lenses and learn about the latest fashions and trends.

An essential part of getting a pair of eyeglasses is the lenses. Lenses are made from three materials: plastic, glass, and polycarbonate. Plastic, the most used material for lenses, is impact resistant and lightweight but partial to easily being scratched. Glass is still used for lenses and is scratch resistant but heavy and breakable. Most everyday use lenses are made of high resin. Hard resin lenses are lightweight, provide good optical quality, and are resistant to scratches. They can also be upgraded with color tints, UV – protectants, or photochromics. Polycarbonate lenses are designed for high impact resistance and are ideal for occupational hazards, children, and athletes. They provide the best eye protection.

Eyewear is considered a medical device and should improve, enhance and protect your vision. In a recent report by the American Foundation for the blind, losing sight was tied with paralysis as the health condition that would have the most negative impact, considered worse than HIV/AIDS, cancer, stroke and several other serious medical conditions. Today’s eyewear can do more than just correct vision; it helps to optimize vision for everyday activities, and plays an important role in protecting and preserving vision for the future.

In addition to choosing the right lenses to correct your vision based on your prescription and frame there are additional features that really do improve your vision and eyewear experiences.

Non-Glare (some opticians say AR coating)

A percentage of light is lost due to reflections that create glare, leading to loss of visual acuity and clarity. A result of decreased light is lower contract sensitivity which affects the patient’s ability to discriminate different shades of gray or objects against a low contrasting background. Glare can also be reflected on the front of the lens prohibiting other people from seeing through your lenses, making it harder to make eye contact and decreasing your cosmetic appearance to others. Some other common situations are:

  • When you have sunglass lenses they have a concave surface on the backside of the lens that acts like a mirror, magnifying the size of reflections
  • Bright office/school  lighting also causes glare to be reflected off computer screens or white boards causing unnecessary eye strain and fatigue
  • Eyeglass wearers driving at night are exposed to glare from oncoming traffic and street lights that cause a reduction in visibility. Often described as halos around these lights. People who are not wearing non-glare lenses and driving at night can have a decreased reaction time to unexpected situations and ability to identify people or objects

Non-glare lenses allow up to 99% of light to reach the eye, improving contrast sensitivity by 20%. The foundation of non-glare lenses is a scratch coat layer that can lengthen the life of your lenses and reduce the amount of surface scratches from daily life or cleaning. The lenses are similar to coatings found on microscopes and camera lenses. Even in the latest exam room equipment the patient’s look through equipment that has non-glare properties during the refraction to eliminate glare. If a patient purchases lenses without non-glare then the vision will already be decreased from what it was when the prescription was written.

How they work: The lenses consist of several layers of metal oxides applied to the front and back lens surfaces. Because of the layering effect, non-glare lenses sometimes have a hint of green, blue or purple color, depending on the individual manufacturer’s formula. Each layer is scientifically calculated to block reflected light. External reflections mask your eyes from a clear, complete view when someone is looking at you. So with a non-glare lens, reflections are eliminated and lenses look thinner or non-existent and your eyes are more visible so you can make better eye contact with others.

Much like progressive lenses there are several types of non-glare and they differ and vary in technology and quality. Premium non-glare has a scratch coat layer that is applied to both sides of lenses where others only apply this layer to the front. Premium lenses will also have a “hydrophobic” surface layer that prevents water spots (rain, snow and fog), making the lens very easy to clean. Then there is the “oleophobic” surface layer that repels skin oils, smudges, dust, dirt and fingerprints with superior anti-static properties. As far as cleaning premium lenses, after about 20,000 cleanings premium non-glare has continued durability, meaning the benefits of the lens do not lessen over the life of the lens, preserving the premium qualities. Other non-glare lenses breakdown over time.

Photochromics

The most popular photochromic lenses are made by Transitions®. When you purchase Transitions® lenses you should receive a certificate of authenticity. This is the vendor’s way of protecting you and them from the distribution of an imitation brand because not all photochromics are the same and they do provide a superior product. These lenses protect you 100% from UVA & UVB rays and this protection is convenient because you do not need to change your eyewear to sunwear when you go outdoors, the lenses change automatically to a sunglass dark tint in seconds. Constant variations in light intensity throughout the day can leave eyes feeling tired and sore. Photochromic lenses reduce discomforting and disabling glare, thereby reducing squinting, eye strain and eye fatigue for wearers. Patients’ eyes will feel more comfortable all day long.

How they work: Photochromic lenses change from clear or light to dark depending on the amount of ultraviolet light they are exposed to. Transitions ® lenses have a front-surface coating that changes color from clear to gray or brown when exposed and the color darkens evenly regardless of the lens prescription or thickness.  Their proprietary dye system called ESP (Enhanced Scientific Performance) fades back 3 times faster than their previous generations. Some photochromic lenses use a different ingredient that when a prescription is stronger the thickest part of the lens will be darker than the thinner parts. Many have improved their offerings but premium product has longer product lifetime, faster darken and fade-back times, quality of tint color and overall performance. It is important to note that since vehicle windshields block UV light, photochromic lenses will not darken while driving. Newer technology is available where the lenses have a slight tint vs. clear when no UV light is present and are able to darken behind windshields. It is recommended that all drivers have a pair of polarized sunwear.

Polarization

There are 3 main benefits to having a pair of polarized sunglasses. One is they are considered a safety driving lens because they eliminate blinding glare from the sun reflecting off roads, signs, your windshield, etc. If you have ever been driving towards a sunrise and had a difficult time seeing clearly, needing to squint or put your visor down, you have experience blinding glare.

The second is the protection against the suns harmful rays as these lenses block 100% of UV rays and some brands even block HEV rays. Did you know that 82% of people know that the sun can damage your skin? Did you also know that only 9% of people know the sun can cause damage to your eyes?

Dangers of Exposure: Extended exposure to the sun’s UV rays has been linked to eye damage, including cataracts, macular degeneration, pingueculae, pterygia and photokeratitis.  New research suggests that the sun’s high-energy visible (HEV) radiation; also called “blue light” may increase your long term risk of macular degeneration. In fact, experts say as much as 80% of our lifetime exposure to UV rays occurs by age 18. The risk of damage to our eyes and skin from solar UV radiation is cumulative, meaning the danger continues to grow as we spend time in the sun throughout our lifetime. With this in mind, it is especially important for kids to protect their eyes from the sun, and generally they spend more time outdoors.

The third is their usefulness in the varied amount of hobbies, sports and other activities. They can enhance your experience and improve your game. Below is a chart on when to choose which lens:

 

Activity Recommended Color(s) Recommended Materials & Styles
Baseball Gray or Green Consider background, day or night games. Mirror coatings reduce the intensity of surface reflections and infrared for a cooler eye while standing in the field. Include back surface non-glare and impact resistant material.
Cycling Most Browns, Some Greens, or Copper to enhance contrast High contrast brown and green to see road hazards, high impact resistant materials for safety. Polarized to reduce scatter and early AM road reflections. Wrap protects from dust and wind.
Driving Gray or Brown Brown to brighten contrast. Non-Glare for clarity. Polarized for safety to remove blinding reflections.
Fishing Brown, Amber and Gray Polarized works best to see into water. Gray is darker and brown enhances contract. Low light, overcast or dusk try amber.
Golf Green and Brown Always non-glare. Newer golf eyewear filters are green or lavender.
Motorcycling Most browns, some gray and green High speed needs high contrast and high impact resistance. Non-glare improves clarity and safety. Polarized may affect instrument visibility, and care in tunnels is needed. Photochromics are great but not polarized.
Skiing Brown and Amber High contrast brown and amber are best. High impact resistance and wrap for high speed. Polarized lenses can improve safety because they show ice as black, snow as white and always need non-glare.

 

Clip-On’s

Clip-On’s are not for everyone but they can be a great solution for the price conscious. It can be difficult as an optician to find a company that provides clip-ons that will fit properly on any frame since frames come in all shapes and sizes. There are manufacturers that sell a frame that comes with a clip attached, this way that clip fits properly on that frame. Sometimes even if there is a clip that fits your frame once your personal prescription and frame are assembled it may not fit properly. This is because lenses are made with curves and the front surface of your lenses may end up with different curves then the backside of your chosen clip; causing the clip to no longer fit because it rocks in place.

There are advancements to clip-ons in the industry. We can know offer a clip-on that is made specifically for any frame and your personal prescription, called a Chemestrie Clip.  What happens is the back surface of the clip is actually created to match the curves of the front side of your lenses so they have a custom fit and will not rock in place. They are also made to the same size and shape as your chosen frame. They attach to your lenses with very small magnets that the wearer doesn’t even notice while wearing. Although they do cost more, it is worth the investment. Along with polarized clip-on’s this manufacturer offers a clip-on that is clear and can be made to your reading prescription; in essence they transform your single vision lenses into readers! They also have 3D clip-on’s, so if you are interested in 3D theatre, TV or gaming but need your prescription while doing so you can just purchase a 3D clip for your eyewear.

Cost

To everyone having a primary pair of eyewear for everyday use and a pair of polarized sunglasses may not be economical, some patients do choose to get everything they need out of one pair of eyewear. Although as opticians we do feel having a primary pair of eyewear, a pair of polarized sunglasses, a back-up pair and possibly another pair for your personal activities or computer use is ideal we also do understand the financial burden. A suggestion would be to purchase your primary pair of eyewear and your polarized sunwear at difference times. Eyewear should be considered an investment in your vision so many facilities will extend a multiple pair discount for possibly even a couple of months. At our facility we extend a discount for three months because we know it is important to have both.

References:
  • American Foundation for the blind, Transitions®
  • Skin Cancer Foundation
  • Healthy Sight Counseling
This article was last updated on 03/2013