POLARIZED SUNGLASSES:
Everyone's Most Important Piece of Equipment Outdoors

By Alexander Bennett

Take a look at any professional athlete competing in an out-door sport: baseball, cycling, golf, fishing, shooting, skiing, tennis, track and field, beach volleyball, sailing… the list goes on. What do they have in common? Most of these athletes wear sunglasses. They are no longer an accessory, but a piece of equipment just as important as the rest of their uniform and gear. It ensures that athletes compete at their best without interruption or distraction. Sunglasses are an essential tool for optimum vision, especially in action sports where split-second decisions mean the difference between winning and losing, or even preventing an accident. These athletes demand the most cutting-edge equipment in order to maximize their performance, and they utilize polarized sunglasses to help them succeed.

However, polarized sunglasses are not limited to the elite competitor. Because of their affordability, they can be used by everyone—even if you aren’t a professional athlete. The reason they are so popular is due to the increased visibility and performance they provide the wearer in everyday situations. While athletes use them to maximize their performance, the consumer can use them to maximize their experience. Whether it’s taking a relaxing hike, enjoying a casual Sunday drive, or relaxing with a book on a beach, polarized sunglasses can eliminate the distracting glare that causes visual discomfort in any sunny situation. Polarized sunglasses can best be described as a sun-glass option for everyone.

LIGHT

The light we see is electromagnetic radiation in the visible spectrum, 380 nm to 700 nm. The invisible radiation discussed in this course will include ultraviolet (UV), and most opticians are already accustomed to discussing this. UV light is electromagnetic radiation outside of the human visible spectrum, has a range of 215 nm to 380 nm and is known to cause damage to the eyes and skin if exposed unprotected for prolonged periods.

Light acts like both a particle and a wave. Photons, the common unit of light, move in a particular vector (a specific speed in a specific direction) but they also oscillate up and down along their path, giving them the properties of a transverse wave as well. Bundles of light reaching the earth from the sun oscillate at all angles, horizontal, vertical and everywhere in between.

Some of this light lands directly on the eye, while some of it is reflected off of surfaces like roadways or water. This reflected light is slightly bent and scattered in all directions according to its angle of incidence on the reflective surface; some of these reflected light rays become polarized.

POLARIZED LIGHT

When a bundle of light hits a flat surface, it becomes polarized, i.e., is reflected only hori-zontally. It becomes concentrated and is blinding to the viewer. This intense reflection is commonly referred to as blinding glare. The reflections can be uniform, like light reflected off of the road ahead of a driver or from another car’s hood. The reflections could also be from non-uniform or changing surfaces, like running water or a non-uniform patch of ice on the road. No matter the case, the desired requirement is to filter out the distracting reflected light and provide a clear viewing experience for the wearer.

POLARIZED FILTERS

The properties of polarized filters are used in a variety of fields such as chemistry, engineering, professional photography, geology and astronomy. As an example, polarized filters can be used to highlight clouds for photographers or detect the amount of stress in lenses in a frame by observing the amount of birefringence (internal stress) induced. This is used in a variety of engineering stress tests and is used in many finishing labs to ensure proper lens fit with minimal stress placed on the finished lens.

One can think of polarized lenses as linearly aligned slit filters used to block incident light of a particular orientation. Think of the filter acting like Venetian blinds: The horizontal blind blocks incoming light from above and below. By blocking this light, it provides a clearer view when looking out a window; there are fewer distractions and reflections observed. For optimal viewing, a polarizing lens should stop horizontally polarized light from view while allowing vertical light rays through the lenses.

As stated, reflected light off flat surfaces becomes polarized in a horizontal direction to the viewer. It causes blinding glare. This light obstructs images from the observer, such as the bottom of a shallow streambed. By eliminating the reflected blinding glare from water, the wearer is able to see below the surface of the water and clearly identify rocks and fish. The advantage in this example is safely avoiding obstacles while wading through the stream, locating the fish one might be trying to catch as in fly fishing or from a boat.

Another instance in which polarized lenses provide an advantage is while driving because of the elimination of glare from oncoming traffic or the road itself. Both the metal finish from other cars and the road itself can be quite reflective on bright days, but this effect is amplified if it has recently rained or snowed. Suddenly these surfaces are reflecting much more light and in many more directions. Polarized lenses filter and reduce the most intense horizontal reflections from these surfaces. This ensures that the wearer’s eyes are relaxed and don’t feel strained, which can result from even a short drive.

DISADVANTAGES OF POLARIZED LENSES

Polarized lenses have never been suitable for pilots of major aircrafts. The Federal Aviation Administration (or FAA) advises pilots against wearing polarized sunglasses. The FAA specifically mentions polarized lenses creating striations and decreased visibility through aircraft windscreens. This can create much more visual noise (a colorful rainbow effect and visual obstruction)

for the pilot. This is extremely important when spotting other aircraft in high-traffic situations during takeoff or prior to landing. Polarized lenses effectively mask the sparkle of light from other aircraft, which is necessary to provide an additional measure of safety for pilots in these high-traffic situations.

The FAA even discourages the use of polarized sunglasses due to reduced visibility of instrument clusters equipped with anti-glare filters. This is a result of newer instruments incorporating LCD technology for digitally displaying flight data such as altitude, pitch and yaw of the plane. A polarized filter can dim or even make gauges disappear entirely, which can result in an unsafe situation for the pilot. The AR surface of the gauge helps reduce reflections from the sun or other lights in the cockpit that might mask the LCD display. However, this AR cannot reduce the problem of polarized sun lenses.

To the average consumer, the largest drawback is the disappearance of LCD screens like smartphones, car gauges, radio displays and gas pumps while wearing polarized sunglasses. LCD displays utilize a polarizer, placed at 45 degrees to ensure proper color contrast and clarity of the picture. This isn’t a problem for the wearer when their lenses are aligned in a parallel orientation to the polarizer in the LCD screen. But when the wearer is looking at an LCD device at a perpendicular angle to the polarizer, the image turns black. The same effect occurs if you hold two polarized lenses at 90 degrees to one another.

While this has been more of an issue in the past when looking at digital displays such as GPS navigation, advances in screen technology displays emit light at various angles to ensure that displays can be seen through polarized lens filters, though potentially dimmed. This is still a critical point of note when choosing lenses for those who work outside and rely on digital displays. I have asked many engineers and construction workers to bring in their digital devices and explore how their screens look through polarized lenses. This has saved costly remakes and patient dissatisfaction from choosing the wrong lenses for their needs.

One other note of importance is that some skiers prefer tinted lenses instead of polarized lenses because of the reduced visibility of ice. Since the reflections are eliminated, skiers might not be aware of the ice until it is too late. Those competing in slalom events need to know where they have to check their speeds to safely take the corners. Although competitive skiers wear goggles for competition, many recreational skiers will wear their sunglasses and go straight from the mountain to their après-ski activities. This is another point of mention with patients who express interest in using their sunglasses on the mountain.

Despite these cautions, the advantages of wearing polarized sunglass lenses outweigh the disadvantages. It is important to consider lifestyle and overall use of the sunglasses to make the most appropriate decisions concerning patient lens selection. It is very important that these limitations are understood and easily explained by the dispensing optician for troubleshooting purposes or to discuss how polarized lenses will work for patients’ specific needs.

WHY POLARIZED LENSES?

The advantages to the consumer are invaluable in creating a better visual experience during daytime activities. First, they remove reflections in the form of scatter (“visual noise” as the reflected short wavelengths are polarized and crisscross over one another). This is called Rayleigh’s Effect and is a major reason that polarized lenses are so comfortable overall. Secondly, polarized lenses increase color saturation to the viewer by increasing edge contrast and color variations of an object. Because of this, environments look more vivid than if observed by the unaided eye: Leaves are a vibrant green, and the sky is a darker hue of blue. By eliminating blinding glare, polarized sunglasses provide visibility of an otherwise hidden object for the wearer. This is important for spotting debris and road imperfections whether on a bicycle, motorcycle or while driving a car.

Anti-reflective coatings, especially on the back surface of polarized lenses, are a requirement for the best sunglasses. These coatings improve acuity while driving and should be recommended to anyone wearing sunglasses when commuting. This option eliminates distracting reflections from objects behind the wearer, most noticeably the image of the wearers’ eye reflected on the inside of the lens, which can obstruct vision. Some premium anti-reflective coatings also prevent harmful UV from being reflected into the eye when the sun is behind the wearer.

In competitive sports, back-surface reflections can get in the way of a critical decision leading to poorer performance or a loss of the event. As a cyclist, I can attest to the importance of the best optics while looking at the road for hours at a time. The visual demand is intense: constantly scanning for debris and imperfections while managing your position next to other cyclists—sometimes only inches away from you. The action is very fast, and split-sec-ond decisions are constantly being made—do you drink water now or press on a bit further? The wrong move could cost you valuable time or your position in the peloton. At worst, it could mean an accident, causing injury to yourself or others. Even an insect can lead to disaster: A bug contacting a rider’s face at 30 mph can be quite shocking and jar the most skilled rider. This is why states without helmet laws will mandate eye protection for motorcyclists.

The acuity polarized lenses can provide to the wearer is also important to mention. Colors look truer and better defined than a neutrally tinted sunglass. Depth perception and horizon differentiation is improved due to this filtration. This makes a big difference to the golfer following a ball bouncing down the golf course or a spectator at a baseball game tracking the ground ball from the infield into the outfield. However, golfers may have difficulty “reading the green” because of the individual grass blade reflections (the grass blades are pointed in all directions) and as a result, many prefer golf-specific tints.

While you don’t need polarized sunglasses to watch these events happen in real time, they are more comfortable and noticeably reduce eye fatigue over the course of several hours of watching the same events.

Comfort is a major factor to wearing polarized sunglasses. The eyes can become tired after viewing the same activity occur for several hours. This is most evident to those with long commutes or individuals who drive for a living—they are fixated for hours at a time on a road emitting horizontally reflected light and blinding glare. This reflection can cause discomfort, sensitivity and distraction. Polarized lenses help to reduce this fatigue by filtering “noisy light” (or distracting reflective polarized light). This can relax the eye, eliminating eye strain and making the wearer more comfortable.

SKIN AND EYE PROTECTION

Part of the necessity of sunglasses is to protect the eyes and the adnexa (the skin surrounding the eyes) from UVA and UVB light. All polarized filters are engineered to block these specific wavelengths of light waves regardless of the material of the lens. However, very light polarized lenses may not be as UV-absorbing as dark sun lens densities. Significant absorption is important for the health of the eye and ensures protection from damaging ultra-violet radiation that is associated with cataract development and retinal damage from prolonged exposure. Large sunglass frames act like a shield, protecting the eye and the sensitive skin around the socket. Sunscreen is used to protect the body from sunburn, so think of polarized sunglasses as sunscreen for the eyes.

The protection from damaging UVA and UVB is necessary for anyone who spends a lot of time around water and snow. Due to the reflective nature of these environments, wearers are subjected to much more incident light radiation than those who vacation or infrequently visit these types of areas.

This is also very important to consider at higher altitudes where the UV and visible light is much more intense. Sunlight includes potentially damaging high-energy blue-violet radiation (415 to 455 nm) of concern by ECPs and a predominant conversation with patients using digital devices. This light, associated with retinal damage is also filtered by polarized lenses. This makes for another crucial talking point when recommending polarized lenses to the wearer.

Polarized sunglasses act like sunscreen for the eyes by blocking these damaging frequencies of light. In fall 2012, Anderson Cooper suffered from sunburn to his cornea (commonly referred to as snow blindness, the clinical term is photokeratitis) while reporting for “60 Minutes.” He was recording a segment from a ship off the coast of Portugal without wearing any eye protection for only two hours. Even with limited exposure to light reflected from the water’s surface, it was enough for him to lose sight in his right eye for 36 hours. While the effects of a corneal burn are temporary, the long-term effects of intense UV exposure could result in cataracts, pingueculae, pterygia, skin cancers or permanent damage to the eye.

Sunglasses can also protect the bones that form the eye socket from projectiles. According to the National Eye Institute, approximately 800,000 total eye injuries occur in the United States annually. Of those total recorded injuries, roughly 100,000 occur while engaged in sports; but it is estimated that 90 percent could have been prevented with proper eyewear. Sunglass manufacturers purposely pair Trivex or polycarbonate lenses in sport frames for maximum protection.

Large sport sunglasses wrapped close to the face can provide maximum eye protection in the event of an impact. A skate-boarder can feel secure knowing that their eyes are protected from dust, debris and grit. Sport shooters can be confident that spent casings won’t become distracting projectiles. Volleyball players can concentrate on setting up their next attack after diving into the sand, not wiping sand from their eyes. Each scenario offers a solution to a common theme—the peace of mind that nothing will compromise the experience.

CONCLUSION

Polarized sunglasses in many ways sell themselves to the consumer. It is important to demonstrate the advantages and to be able to explain how polarized lenses will benefit the wearer whether they are recreating or competing. Reinforce to the viewer that polarized sunglasses ensure the highest quality of vision to maximize both their performance and experience. This way you will strategically align your practice to sell more polarized lenses, because polarized sunglasses are truly everyone’s most important piece of outdoor equipment.