Unless we experience eye pain or vision problems, most of us take seeing for granted. But vision is a remarkably complex process: your eyes are constantly moving and changing to adjust to the conditions in front of them. When they are forced to cope with adverse conditions such as strong ultraviolet radiation or glare from bright sunlight, your pupils contract and your eyelids squint. It's no wonder that many people experience eye strain, vision-related headaches or various eye diseases at one time or another.
Quality sunglasses can reduce or eliminate many of the problems caused by over-exposure to bright sunlight and ultraviolet radiation. Good quality lenses with appropriate tints can selectively block the wavelengths of light that cause most vision problems, protecting the wearer from cataracts and other eye problems.
Types of Lenses:
Probably the most commonly used lens material, acrylic lenses are lightweight and relatively inexpensive to produce. Acrylic is available in both tinted and mirrored lenses, and is also used clear, for reading glasses and goggles. "AC" and "CR39®" are types of acrylic.
Most often found in top-quality sports glasses, polycarbonate lenses are lightweight, impact-resistant and the most scratch-resistant of the plastics. The "bullet-proof" plastic known as LEXAN® is a type of polycarbonate.
Optical-quality glass lenses are ground and polished to the precise thickness necessary to provide minimal distortion and maximum clarity. The hardness of glass makes it the most scratch-resistant lens material presently in use. Glass is also the heaviest lens material.
Lens Tints and Coatings
Smoke, Gray and Gray-Green tints
Are the most common type of lens color. They are effective at blocking glare without changing color perception, making them a good choice for all-weather use.
Amber, or Brown lens tints
Are especially good at blocking the blue light commonly found in diffused light such as one might experience on a cloudy day. Amber can improve both contrast and depth perception, and is a good all-around choice if you live in an area with changeable weather patterns.
Like Amber, Yellow and Yellow-Gold tints improve contrast and give a sensation of heightened visual acuity. So-called "Driving" lenses are usually amber or yellow-brown.
Help block blue light, thereby improving contrast. Many people feel that rose tinted lenses are more comfortable for long periods of time than other lenses.
When sunlight bounces off a reflective surface such as glass, water or snow, the result is glare. Glare can be much brighter than the light that caused it, and can irritate or even damage the unprotected eye. Polarized lenses block vertically-reflected light by horizontally aligning the crystalline structure of the lens. This makes them ideally suited for use around water, snow, and for driving. Avoid cheap polarized glasses, because poorly matched lenses may result in eye strain.
Are good at blocking glare without changing color perception. Quality mirror coatings are effective, but beware of very cheap mirrored sunglasses, as they may trick your eyes into allowing harmful radiation into the interior of the eye.