Tennessee Consumer Decision Judging Guide Sunglasses If it’s a bright, clear day outside, you may instinctively reach for your sunglasses, when you head outside. Choosing sunglasses for eye protection allows a wide range of choice. Knowing what features are available will help in finding the best pair of sunglasses for the conditions in which they will be worn. There are four things that a good pair of sunglasses should do for you: 1. Sunglasses provide protection from ultraviolet rays in sunlight. Ultraviolet (UV) light damages the cornea and the retina. 2. Sunglasses provide protection from intense light. When the eye receives too much light, it naturally closes the iris. Once it has closed the iris as far as it can, the next step is squinting. The result of too much light is damage to the retina. A good set of sunglasses can block light from entering the eyes thereby avoiding damage. 3. Sunglasses provide protection from glare. Water and some surfaces can reflect a great deal of light. These reflected spots can hide objects and be distracting, especially to drivers. 4. Sunglasses eliminate specific frequencies of light. Certain frequencies of light can blur vision and others can enhance contrast. Choosing the right color sunglasses enables them to work better in certain situations. Light Much of the concern over eye health involves the shorter wavelengths, called ultraviolet (UV) light. UV light is divided into two categories- (1) shorter wavelengths are called UVB, longer wavelengths are called UVA. Shorter waves have been found to cause more eye damage than longer waves. The main protection offered by sunglasses is filtering out these UV rays. The dark color of the lenses does not necessarily mean the sunglasses will filter out the UV rays. Although sunglasses offer some protection, they do not offer complete protection. Some styles of frames do not prevent unfiltered rays from reaching the eyes from the sides, top, and/or bottom of the glasses. Sunglasses also provide some protection from dust and particles in the air. It is more important for persons with light colored eyes to wear sunglasses for protection than persons with dark eyes. The lighter the eye the more sensitive to direct light. When we talk about light in reference to sunglasses, three types of light are important. 1. Direct Light—direct light is light that goes straight from the light source (like the sun) to your eyes. Too much direct light can wash out the details of your surroundings and make it almost painful to try to focus your vision on anything. 2. Reflected Light—Reflected light, usually in the form of glare, is light that has bounced off a reflective object to enter your eyes. Just like direct light, strong reflected light can make it difficult to perceive the details or directly view an object. Snow, water, glass, and white sand are all good reflectors. 3. Ambient Light—Ambient light is light that has bounced and scattered in many directions so that it does not seem to have a specific source. A good example of ambient light is the glow in the sky around a major city. It would be very hard to identify a single source of light for that glow. Ambient light is how you are able to see when there is no direct source of light. Lens Colors The color of the tint determines the parts of the light spectrum that are absorbed by the lenses. Color doesn’t affect UV blocking. Different colors produce specific results: • Gray—Gray tints are great all-purpose tints that reduce the overall amount of brightness with the least amount of color distortion. Gray lenses offer good protection against glare, making them a good choice for driving and general use. • Yellow or gold—Yellow or gold tints reduce the amount of blue light while allowing a larger percentage of other frequencies through. Since blue light tends to bounce and scatter off a lot of things, it can create a kind of glare known as blue haze. The yellow tint virtually eliminates the blue part of the spectrum and has the effect of making everything bright and sharp. That’s why snow glasses are usually yellow. This tint really distorts color perception, which makes it inappropriate for any activity that relies on accurate color. • Amber and brown—Amber and brownish tints are also good general purpose tints. They have the added benefit of reducing glare and have molecules that absorb higher frequency colors, such as blue, in addition to UV rays. There has been research that suggest that near-UV light frequencies such as blue and violet can contribute to the formation of cataracts over time. • Green—Green tints on lenses filter some blue light and reduce glare. Because green tints offer the highest contrast and greatest visual acuity of any tint, they are very popular. • Purple and rose—Purple and rose tints offer the best contrast of objects against a green or blue background. They make a good choice for hunting or water skiing. Lens color can be a dye in the lens or a coating on the lens. Color on coated lenses is more likely than dyed lenses to scratch or wear off. Coated lenses can be protected by the manufacturer through use of scratch –resistant layers. Overall dyed lenses retain color longer. Darkness of a lens determines how much visible light will be let in. If glasses are to be worn in very bright conditions such as for water sports a darker lens is more practical. For everyday wear, a medium to light lens is usually sufficient and may be more versatile. The main point is to match the amount of tint to the purpose for which the glasses will be used. Types of Lenses • Plain—Plain lenses are uniformly tinted throughout the lens and come in lots of different colors. The darkness of the lens has nothing to do with how well it blocks UV light, but it will make a difference in how much visible light gets seen. This may be important for eye comfort during prolonged time in bright sunlight. • Single gradient—Single gradient lenses are tinted darker at the top than at the bottom. They may be useful for tasks like driving, where the road is bright but the dashboard is dark. They are useful for places like a beach, where light is reflected up from the sand. The difference in tint causes lighting to change as the wearer’s head moves, which may be annoying to some wearers. • Double gradient– Double gradient lenses are tinted darker at the top and bottom, but lighter in the center. These are designed for sports such as sailing, skiing, and tennis, where light comes in from above and is also reflected from below, but the center of vision has less light coming in. There are not appropriate for driving, since they darken visibility of the dashboard controls. Like single gradient lenses, the difference in tint may be annoying to wearers. • Polarizing—Polarizing lenses are specifically designed to reduce reflected glare, such as sunlight bouncing off water or pavement. This makes them especially suited to water sports and driving. • Photosensitive– Photosensitive lenses darken and lighten in response to the amount of available light. These lenses have millions of molecules of substances, such as silver chloride or silver halide, embedded in them. Photosensitive lenses darken more quickly than they lighten. They also do not darken as quickly in hot weather as in cold. They will not darken much while driving, since the car shades out much of the direct UV light to which the lenses respond. Lenses that start out with a dark tint will be darker when they change tint. Some wearers may be bothered by the length of time the lenses take to change. In addition, some lenses “wear out” and fail to darken or lighten after a period of time • Flash– Flash lenses have a mirror like finish on one side of the lens. It may be silver, colored, or iridescent. The coatings add more to appearance than usefulness and can scratch easily. • Polarized—Polarized filters are most commonly made of a chemical film applied to a transparent plastic or glass surface. When applied uniformly to the lens, the molecules create a microscopic filter that absorbs any light matching their alignment. Most of the glare that causes you to wear sunglasses comes from horizontal surfaces. When light strikes a surface, the reflected waves are polarized to match the angle of that surface. So, a highly reflective horizontal surface, such as a lake, will produce a lot of horizontally polarized light. Lens Material There are several types of lens material. CR-39 is a plastic made from hard resin that meets optical quality standards. Polycarbonate is a synthetic plastic material that has great strength and is very lightweight. These lenses tend to be lighter and are more impact-resistant. Glass lenses are heavier but are more resistant to scratches. Quality Optical-quality polycarbonate and glass lenses are free of distortions, such as blemishes or waves, and have evenly distributed color across each lens. For most purposes, like going to the beach or driving, look for a tint that absorbs or blocks 70% to 90% of light. Tints that offer less than 60% blockage are mainly good for fashion since they offer only mild protection. Anti-reflective, waterproof, mirror and scratch-resistant coatings improve the functionality of the sunglasses but also add coast. Many of the more expensive sunglasses use Specific technologies including polarization, tinting and anti-reflective coatings to achieve increased clarity, better protection, higher contrast or to block certain types of light. Frames Normal frames similar to prescription eyeglass frames filter the light coming through the lenses but offer no protection from ambient light, direct light and glare from other angles. Wrap-around frames, larger lenses and special sidereal attachments can keep this extra light from your eyes. The material used to make the frames is often a huge factor in cost and durability. Most inexpensive sunglasses use simple plastic or wire frames, while name-brand sunglasses use high-strength, light-weight composite or metal frames. Also, the better sunglasses usually have features like tension springs that connect the arms to the face instead of just screws. Labeling The American National Standards Institute (ANSI), in cooperation with the U.S. Food and Drug Administration and the Sunglass Association of America, has set up a voluntary labeling system for sunglasses. Manufacturers may choose whether or not they wish to use the labeling system. Sunglasses are regulated by the Food and Drug Administration (FDA) as medical devices. Recommended standards include: • Sunglasses must block 99% of UVB light. A UVB-blocking sunglass is adequate to protect eyes in moderately bright sunlight like that found in low-altitude, urban areas. • A UV-blocking sunglass blocks 99% of both UVA and UVB. A UV-blocking sunglass is adequate protection in very bright sunlight like that found in low- altitude snow areas and beaches. Such sunglasses reduce glare and increase visual comfort. The lenses should allow you to recognize traffic signals accurately. • To protect eyes during prolonged daily use in extremely bright sunlight, like high-elevation snow areas and equatorial sand beaches, a UV-blocking sunglass should block 92 to 97% of visible light and have side shields. Goggles are also acceptable. Side shields are needed in extremely bright sunlight to prevent UV rays and light from being reflected into the eyes. These sunglasses limit a drivers ability to accurately recognize traffic signals. Side shields should not be worn when driving because they eliminate peripheral vision. • The only medical claims allowed on sunglasses are that they prevent cataracts and photo keratitis. Tips Remember that the most important protection factor by far has to do with how often you actually choose to wear your sunglasses. So you need to consider ALL the factors that will influence your desire to keep them on your face. • It is essential to understand what “the right choice” means. It’s actually very simple. The “best” sunglass is the one which you will actually WANT to wear most of the time when outdoors, especially in the sun. • Don’t underestimate the importance of style. How we see ourselves and how we seek to enhance our appearance is for many the most important factor in maximizing actual use. • Fit and comfort are crucial. Take time to try on sunglasses and consider how they feel. They should be comfortable and secure. Just like trying a new pair of shoes, take the time to fully experience the fit. Remember, a high performing UV blocking lens does not protect if it’s on the dashboard, in your purse, or slipping down your nose. • Don’t forget to look through the lenses and let your eyes be the judge of how well you can see. If possible step outside and look at both light and dark areas. You want a lens that is dark enough to protect against glare and be comfortable in bright light, yet not so dark that it compromises your vision in low level light situations. • Remember, a major purpose of wearing sunglasses is glare reduction in normal sunlight activity. Sunglass lenses are impact resistant as required by FDA but they are not shatterproof. Kids Children may not be as interested as adults are in the fashion aspect of sunglasses. But because kids spend much more time than most adults do outdoors and in direct sunlight, UV protection for the eyes is extra important. In fact, may experts believe our eyes get 80% of their total lifetime exposure to the sun’s UV rays by age 18. Since excessive lifetime exposure to UV radiation has been linked to the development of cataracts and other eye problems, it’s never too early for kids to begin wearing good quality sunglasses outdoors. References Beyond Fashion: Why You Gotta Wear Shades. http://newswise.com/articles/ view/540549 Children, Teens at Greater Risk Than Adults of Exposure to Damaging UV Radiation. http://earthtimes.org/articles/show/children-teens-at-greater- risk,384997.shtml How Sunglasses Work. http://science,howstuffworks.com/sunglass.htm Kids need sunglasses, too. http://consumerreports.org/cro/babies-kids/child- safety/outdoors/sunglasses-for… Sunglass savvy. http://consumerreports.org/cro/health-fitness/beauty-personal- care/sunglass-savvy-705/ove… Sunglasses. (1997-98). Consumer Decision Making Contest Study Guide. University of Georgia Extension. Sunglasses & You: Seeing Your Way Through the Confusion of Sunglass Selection. http://sunglassassociaiton.com/trial/SunAndWe.html Sunglasses for Kids. http://www.allaboutvision.com/sunglasses.kids.htm Adapted by: Annette Cole, University of Tennessee Extension, Stewart County 2008. The University of Tennessee Extension offers its programs to all eligible persons regardless of race, religion, color, national origin, sex, age, disability or veteran status and is an Equal Opportunity Employer.
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