By Grant Brown
What makes a good pair of sunglasses?
Protection surprisingly is not considered first! That honor goes to actual use. The best protection won’t help if the sunglasses are not used consistently.
The second consideration is protection. It’s certainly recognized that 99%+ elimination of UVA and UVB radiation is paramount. Ultraviolet A radiation (UVA)—the lower energy ray—can pass through the cornea and is linked to certain types of cataracts. It may play a role in macular degeneration.
Ultraviolet B radiation (UVB)—a higher energy ray, has a negative effect not only on the structures of the conjunctiva, cornea and lens but also on the thin, delicate skin surrounding the eye. This skin is susceptible to many of the most common types of skin cancers. UVB rays, too, are the ones that cause premature aging and wrinkles around the eye.
In addition to the UVA and UVB radiation, eye specialists are becoming concerned about high-energy visible (HEV) radiation, which has the shortest wavelength and the highest energy portion of visible blue light. This high-energy blue light passes through the cornea and lens and potentially has its maximum negative impact directly on the retina.
Reflected UV, up to 100% from water, 85% from snow and 25% from sand, concrete or pavement adds that much more to direct exposure from the sun. Eye protection from the sun is equally important to those with dark skin who, while having a lower risk of skin cancer from the UV radiation, are considered to have the same the risk of eye damage from UV and HEV radiation as someone with fair skin.
Polarization, like the color of the lens, actually does not relate to UV protection other than that most polarized lenses on the market do filter UV, too. There is no question that the eye is more comfortable and acuity is better through the reduction of glare from the water, sand and pavement with polarized lenses. Safety while driving, though, is the most important reason optical professionals recommend their consistent use. The elimination of reflected glare on the windshield minimizes interference while maximizing accurate, safe vision.
The third component, however, causes the biggest controversy. It is true that a large portion of even basic “drug store-type” sunglasses lenses have UVA and most have UVB protection. For that particular requirement, price is not a major factor. Unless specified (i.e., “540 or 580 nm (nanometer) filtering”) most of these lenses do not screen for the HEV component. It is also true that the vast majority of these low-cost sunglasses have stamped or pressed lenses, which may be either already warped or likely to warp and distort vision easily. Even minor imperfections and/or warping of these lenses can cause a loss of visual acuity. The clearest, and more expensive, sun lenses are manufactured the same as prescription lenses and have the quality of materials, construction and consistency of tint.
Last are the frames. Inexpensive frames usually do not fit well and are not designed to be adjusted for comfort or to minimize UV exposure from the top, sides or bottom of the lenses. When purchasing a quality frame, however, fit, durability and adjustability can be considered, which, when combined with quality lenses, yield the best possible eye protection.
Note to contact lens wearers: many brands of contacts are marketed as having a UV filter built into the contact lenses themselves giving the impression that sunglasses are not necessary. While UV filtering contacts may offer some protection to the cornea and inner eye structures, they do nothing to prevent damage to the conjunctiva, lids and the delicate skin around the eye. These contacts can give a false sense of safety and protection.