Sunglasses

About Sunglasses

Sunglasses may seem like just another beach accessory, but they have an important job to do: protecting your eyes from harmful ultraviolet rays, and reducing glare so you can see comfortably.

Ultraviolet rays (UV) are an invisible form of radiation found in sunlight, and over-exposure to UV light can cause significant eye damage, resulting in a loss of vision, and the possible formation of cataracts.

Glare is the result of a process known as polarization. When visible light hits a surface, some of it is absorbed, and the rest is reflected back in what our eyes perceive as an uncomfortably bright haze.

Road/pavement, water, sand, and snow are especially reflective, and the glare from these mostly horizontal surfaces is the most common reason many people feel the need to reach for their sunglasses in the first place.

Not All Shades are Created Equal

It's important to know the difference between shades that do the job, and those that don't.

A high quality pair of sunglasses should be able:

• Block 100 percent of UVA, and UVB light.
• Significantly reduce or eliminate glare.
• Improve, or at least preserve contrast.

A low quality pair of sunglasses will likely:

• Reduce some of the visible light, but not actually filter out the UV rays.
• Fool your iris into opening wider, which actually admits more of the harmful rays that can lead to eye damage.

The Quick Check

A quick look at the attached tag may reveal a hint about performance quality.

In order to make the case for a higher price tag, high-performance shades nearly always advertise enhancing features such as the percentage of UV blockage, polarization, mirroring, and scratch resistant coating.

Lesser sunglasses will usually carry a bargain price tag, and give little or no additional information.

Lens Features

Let's take a look at some of the many options that can be combined to produce your ideal pair of shades.

Lens Material

Available in both prescription, and non-prescription strengths, lenses are typically made from either glass, high quality polycarbonate, or CR-39 plastic. Glass is more scratch resistant, but is a bit heavier than the lighter weight plastic lenses.

Protective Coatings

Additional coatings improve the performance, and level of protection a pair of lenses has to offer.

• Scratch resistant coating greatly improves the durability of polycarbonate lenses.
• UV block coating is a must have feature to provide any significant protection for your eyes. Lenses that provide 60 percent or less UV blockage are strictly for fashion purposes only.
• Mirror coating actually reflects more visible light than lenses that lack this feature, helping to reduce glare. However, without UV blockage, mirroring alone isn't enough to protect your eyes from serious damage.

Polarized Lenses

Polarized lenses are the most effective for eliminating glare. Here's a quick explanation of how they work.

The reflection of light when it hits a surface is actually called polarization. There are two types of polarized light, vertical and horizontal. Horizontal polarization is the light reflected from semi-flat surfaces such as the pavement and sand mentioned earlier, and it is this type of light that causes that unpleasant glare.

Polarized lenses either reduce or eliminate horizontal glare, but still admit vertical polarization. If you're wondering if a pair of lenses has been polarized, here's a fast way to tell.

• Hold the lenses up to a reflective surface so you can look through them, with the arms of the frames pointed at three and nine o'clock.
• Rotate the lenses so the arms now point to twelve and six o'clock. As you rotate, the light passing through the lenses should brighten a bit. Rotating them back to three and nine o'clock should result in heavier filtration. This is the effect of lenses that have been polarized.

Tints

The frequency of a wave of light is expressed to the naked eye as a color, so the tinting of your lenses has a direct effect on the kind of light they block out. Blocking a certain color can provide greater eye protection, and in some cases even sharpens contrast, making it easier for you to see, and so different tints are used for different situations. The following table should only be considered a general guide.

About Photochromic Sunglasses

Due to the effects of a chemical called silver halide, photochromic lenses have the ability to darken when exposed to UV rays, and return to their original transparency when light is less intense. This ability makes them an ideal solution for those who depend on prescription eyewear, but aren't fond of clip-on shades.

Conclusion

As you can see, a lot goes into the production of a high performing set of sunglasses. We hope you now feel armed with the necessary info to pick out a pair of shades that not only look terrific on you, but also give you the protection you need.

Quality Sunglass Manufacturers/Retailers

• Oakley
• Ray-Ban
• Bolle
• Technical-Gear.com, sport sunglasses.
• SunglassesGiant.com, an amazing assortment of brand name eyewear.