Remember that commercial? I do. Once merely cool summer accessories, whether Foster Grants, Raybans, BluRays or Guccis’ brown tint, cat-eye sunglasses, sunglasses are now a vital element for eye protection against the sun’s damaging rays.
Let’s face it; we are burning up the Earth’s ozone layer, which has caused increased levels of UV light. Sunglasses prevent permanent damage to the eyes, keeping certain wavelengths of light from entering the eye. So, instead of just giving you a confident, savvy look, they reduce the amount of light entering the eye, protect against harmful UV light, decrease glare and increase contrast. Not only is this especially helpful when driving, experts agree that sunglasses prevent permanent damage and urge everyone to wear them when outdoors.
People who spend excessive hours in the summer sun without protection have an increased risk of developing eye conditions in later life, such as macular degeneration, cataracts and corneal problems. And something you might not know, just as light-skinned people are advised to use more skin protection, people with light-colored eyes might need stronger eye protection, because they have less pigmentation and are more susceptible to UV damage.
Here is what “How Stuff Works” has to say about sunglasses:
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 much more resistant to scratches. There are several other materials, such as Oakley’s Plutonite plastic, that have been developed by specific manufacturers.
Lens quality
Optical-quality polycarbonate and glass lenses are free of distortions, such as blemishes or waves, and have evenly distributed color across each lens. Here’s an easy way to tell if the lenses in a pair of sunglasses are of good quality. Find a surface with repeating lines, like a tiled floor. Hold the sunglasses a short distance away from your face and cover one eye. Look through one of the lenses at the lines while moving the sunglasses slowly from left to right and then up and down. The lines should stay straight as you look at them. If they wiggle or waver in any way, then the lenses are not optical quality and will distort your vision. Distortion is extremely common in cheap sunglasses.
Lens darkness
What you plan to use the sunglasses for determines the darkness of the tint. For outdoor sports such as mountain climbing and snow-skiing, you want a tint that blocks most light. For most purposes, like going to the beach or driving, look for a tint that absorbs or blocks 70 percent to 90 percent of light. Tints that offer less than 60-percent blockage are mainly good for fashion since they offer only mild protection.
Special coatings or features
Anti-reflective, waterproof, mirror and scratch-resistant coatings improve the functionality of the sunglasses but also add cost. 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.
Frame and lens design
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.
Which is best?
Dark lens do not necessarily have more UV protection. More and more pressure is being put on sunglass vendors to offer maximum ultraviolet (UV) protection and specify the amount of protection offered.
Look for lenses that absorb 99 to 100 percent of UV light, particularly UV-B, and have the AOA’s (American Optometric Association) Seal of Acceptance. An ultraviolet-blocking coating can also be placed on any lens, regardless of the degree of tint. However, a coating does not block as much UV light as the protective lens.
Good UV protection does not have to be expensive. High levels of protection can be found along the price spectrum. Absorptive lenses come in a wide array of tints, with varying degrees of light transmission. They are available in a large assortment of designs that can fit over glasses, slip behind regular glasses, clip on or flip up.
To prevent irreversible damage to the eyes everyone should wear sunglasses, as well as hats or visors. And don’t forget your babies and young children! Their eyes are most susceptible to UV damage because the eye’s lens has not yet begun to cloud.