The Evolution of Sunglasses and Understanding Lens Material
With modern technology and improvements, sunglasses continue to evolve. It is important to understand that the different materials used in sunglasses have a direct effect on durability, weight, clarity, and, of course, cost. Glass, though rarely used, is heavy, typically scratch-resistant and provides superior clarity; NXT polyurethane also provides excellent clarity, lighter in weight than glass, also is impact-resistant, but is also costly; the more affordable polycarbonate synthetic plastic has very good optical clarity, is lightweight, and is much more affordable; and lastly, acrylic is a great alternative to polycarbonate for casual or occasional use, but is not as durable, and has less optical clarity than the above-mentioned materials.
Lenses should be free from distortion, visual quality is essential, and should not be compromised. Good quality lenses should have no waves or blemishes when looking through them, and color should be evenly distributed. If objects waver while looking through the lenses, there will distortion and there will be very little optical quality.
Inexpensive vs. Expensive
Though cost may be a factor when choosing sunglasses, a good pair should work to provide several essential benefits. Ultraviolet light is very damaging to the retina and cornea, sunglasses should give adequate protection from the suns UV rays, and should protect from glare. There are surfaces that reflect light more than others, and glare is not only distracting, but objects may not be entirely visible; sunglasses should protect against sharp penetrating light. Good shaded lenses should block intense light from entering the eyes; and sunglasses should work to enhance contrast, thereby eliminating uneven light, which can blur vision.
Different Colors or Tints
The color or tint of the lens is as important as the material used. Lenses are tinted to decrease overall brightness, enhance topographical definition, and offer some level of protection from the UV rays from the sun.
Shades of yellow or gold help reduce blue light—the part of the spectrum that causes light to scatter or bounce off of objects, gives very little overall protection against brightness, but is a good choice for moderate-to-low light conditions. The depth perception is excellent, and a good choice for snowboarding, skiing, as well as other snow activities. They work well in flat-light conditions, providing enhancement for contrasts, but does distort color perception.
Amber and shades of brown work well for non-specific conditions, such as snow, and are good for general purposes, effective in reducing glare, and provide good contrast and clarity. These colors help absorb shades of blues and violets, as some research has shown that blues and violets may contribute to cataracts. Such research led to the creation of Blue Blockers.
Grays are more neutral, and though gray provides the least amount of color distortion, shades of gray give good protection against glare, and work well when driving.
Green tints are also considered neutral. Shades of green help filter out blue light, and is effective in reducing glare without color distortion, and does offer good visual acuity. The darker shades work well to reduce eyestrain in moderate-to-light conditions.
Rose or the shades of reddish-orange of vermillion, give a rosy glow to the world, and are also good for snow activities. They enhance the visibility of things against green and blue backgrounds, and work well when driving.
Some sunglasses have a flash or mirrored coating, which is a reflective film that is applied to the surface of the lenses. The light bounces off the surface, thereby reducing the glare, however, the coating make objects appear darker than they are.
If you are particularly sensitive to glare, or if you take part in water sports, then polarized lenses would work well. Intense penetrating glare happens as light reflects, transmits, scatters, or bounces off flat surfaces, such as a body of water, and radiate out in different directions. Polarized filters are a chemical film that is applied directly to the lenses, and when applied properly, will absorb the light that bounces off the surface, significantly reducing the blinding effect.
Some sunglasses have various coatings, such as anti-reflective, scratch-resistant, or ultraviolet coatings. Always check to see if the lenses are coated, if so, what kind, and to what degree. Shaded lenses with an effective UV coating can filter out and eliminate harmful UV rays.