Regardless of style, sun glasses should protect your vision. Recent scientific advancements have greatly expanded understanding of the eye, creating materials to defend them.

The bright light of a cloudless day can be painful and distracting, so most people wear sunglasses when outside, especially while driving. At the other end of the spectrum, fog and smoke decrease visibility. The amber-colored lenses of recent decades filter out the additional blue light scattered by low-lying clouds, giving drivers a more balanced, clearer view of the road. Polarized sunglasses help cut down the glare of reflected light.

Ultra-violet radiation (known as UVA and UVB) has been shown to be a contributing factor for cataracts and many other eye problems. Look for UV-rated sunglasses, which block at least 70-percent of UVA and 60-percent of UVB light. Some sun glasses claim to block 100-percent of both.

The other main danger is impact damage. Flying debris ranges from annoying (specks of dust) to sight-threatening (pebbles kicked up by passing cars). The American National Standards Institute (ANSI) is a private organization dedicated to producing quality goods in the USA. For sunglasses, ANSI requirements include dropping a 1-inch steel ball on the lens from four feet high and shooting a quarter-inch ball at 150 feet per second. If no part of the lens touches the eye when impacted, the glasses pass the test and may advertise themselves as ANSI compliant. This is especially useful in sport eyewear.

Sunglasses are one item where the highest price doesn't always mean the best product. Some designer glasses may not include the safety features that your eyes deserve. Of course, at sourcingmap.com, discount sunglasses and designer sunglasses can be synonymous.

By the way, when buying sunglasses online, you may find that so-called discount sunglasses, allegedly from top designers, are, in fact, cheap knock-offs instead of the real deal. If so, the chances of a refund are pretty slim, so buy from a reputable dealer like Overstsock.com, one with a long history of selling authentic, quality products.

Basically, sun glasses are made from two components: the lenses and the frames.

Frames can be nothing more than thin metal wires that just surround the lenses, or they can be large plastic casings that cover much of the face. Most frames are basically flat, so they can be folded into a pocket, but some prefer the wrap-around styles that fit snugly against the head, entirely enclosing the eyes in shadow.

Lenses come in almost every color of the spectrum. Polycarbonate lenses are especially valuable when working in hazardous environments, as they are darn near indestructible.

Higher end sunglasses usually come with a case and a cleaning cloth. Don't throw them away even if they seem unimportant. The case will protect your new glasses far better than your pocket. The cleaning cloth will clear the sweat and dust off your lenses with the least probability of scratching them. You can also look for lens cleaning solution or wipes that will make your lenses spotless and streak free.

Common sunglasses questions

1.Are mirrored lenses better?

That depends on your attitude. If you're looking to hide your eyes like the Chinese who invented sunglasses, mirrored lenses are definitely the way to go. As for reduced glare or UV protection, they are no different than colored lenses.

2.What about gradient lenses?

These have a lot of color on the upper half and less (sometimes no) color on the lower half of the lens. If you're activities vary and you need clear vision mixed with your eye protection, these can be a useful alternative.

3.What about prescription sunglasses?

Prescription lenses are very common, and generally cost little more than other corrective eyeglasses. Prescription sunglasses are great for those who want to participate in outdoor sports but to not want to wear contacts as contacts can often become dry and irritate the eye.

4.What about Photochromic lenses?