Eyestrain is always a factor when I get a headache, and the glare off of water is a situation that will set off a dash for ibuprofen faster than any other factor. Unfortunately, having the right pair of sunglasses is not as simple as it might appear and one pair doesn’t meet all needs. With all of the brands, styles and lens configurations, selecting a pair of sunglasses can be confusing.
Many people pay more attention to how they look in a pair of glasses than form and function, and consequently they are only happy with their choice when they look in a mirror. If you want performance as well as good looks, consider these factors before selecting your next pair - shade, tint, polarization and fit.
Choose a lens shade relative to intended use. Generally speaking, in an around town, a light to medium tint is adequate. While on the water, near white sand or snow-covered fields a darker shade provides more comfort. Ultimately, the amount of light a lens should transmit relates to the brightness of the environment and individual comfort. Individual is the key element to that statement, since we all have varying degrees of sensitivity to light.
Bright flashes off of water, snow or shiny surfaces subject the eyes to 10 to 12 times more light than required to see, which can be painful and dangerously distracting. To be certain that sunglasses will be adequate for flocking glare, try them on in front of a mirror. If you can see your eyes, they are probably not dark enough to block glare. For comfortable vision on bright, sunny days, sunglasses should block 75 to 90% of visible light. Lens tinting should be uniform, not darker or lighter in spots. With gradient lenses, the tint should lighten gradually and uniformly throughout the transition area. The advances of technology have increased the number of options available to you in terms of the degree of shading as well as the style.
• Solid tinted lenses are evenly tinted across the entire lens to cut glare from all directions.
• Gradient tinted lenses are darker at the top and lighter at the bottom to cut overhead glare and provide clearer vision straight ahead and when looking down.
• Double gradient lenses are darker at the top and bottom and lighter in the center to cut overhead and reflected glare from the ground and provides clearer vision and straight ahead.
• Mirror-coated lenses reflect light across a wide spectrum including the infrared or heat rays (IR) and may tend to be somewhat cooler to wear in both a physical and aesthetic valuation. Mirror coated lenses have a thin layer of vaporized metal that is bonded to the lens’ surface in a vacuum chamber. Metalized coatings, which often use chromium, are less durable than high-performance dielectric coatings that use titanium or quartz. Metal or mirror coatings tend to darken sunglasses uniformly.
• Photochromic lenses appear lighter indoors since they darken in sunlight and fade indoors to provide comfort according to the brightness of the environment. This is a convenient option for prescription wearers, however, in my opinion, they do not darken enough to be acceptable in extreme glare. The amount of light a photochromic lenses transmits varies greatly with each manufacturer and even the darkest lenses aren’t adequate for bright or reflected light. Prescription lens wearers should consider options such as Cocoon or Fitover glasses that they can wear over their existing glasses.
Under various conditions, lens tint can be a major factor, to both function as well as comfort; and for fishermen, polarizing lenses are a must. When selecting a tint, keep in mind that some colors are not recommended for use while driving due to the problems they can cause in recognizing the color of traffic signals. If you are uncertain that the sunglasses you intend to purchase meet traffic signal recognition requirements, read the labeling to determine if there are statements recommending that the sunglasses should not be worn while driving. Here is a breakdown of the most popular tints and situations where they perform best.
• Gray is a popular neutral color that allows true color perception. Gray is a good color for general purpose tinting but it does not enhance contrast. Gray is a good tint for golf, cycling or running.
• Green provides true color perception and is a popular neutral, general-purpose color tint. Generally, green provides a fair degree of contrast in low light and reduces eyestrain in bright light.
• Brown is a better tent in hazy sun. Brown enhances contrast and is a good tint for high-glare sports, such as skiing, fishing or sailing.
• Amber blocks blue light and brightens cloudy, hazy or foggy days. It makes everything look yellow or orange and provides excellent contrast, minimizes eyestrain. Amber is a good tint for fishermen, pilots and skiers.
• Yellow provides enhanced depth perception and contrast in low light. Yellow is also a good tint for trap shooting or sporting clays. Yellow intensifies objects against a blue background and really makes the clays stand out.
• Vermilion is an excellent tent for increased depth perception in low light. Vermilion increases contrasts of objects against blue and green backgrounds.
As the name implies, sunglasses are intended to be worn in the sun, and darkly tinted glasses should never be worn while driving at night. So-called night driving glasses are generally amber tinted eyewear meant to reduce the glare of oncoming headlights. While they may make the driver feel more comfortable, they reduce visibility of the darker portions of the roadway and are not safe, especially in areas where deer often dart from the roadside into oncoming traffic.
Sunglasses are intended for use in the attenuation of bright sunlight. They are generally worn while driving during daylight hours or while participating in general recreational activities. The degree to which sunglasses will attenuate sunlight and block UV rays varies with the physical, chemical and optical properties of the lenses.
When selecting sunglasses, it is a good idea to test the optical quality of the lens by putting on the sunglasses and viewing a vertical edge or line. Move your head back and forth allowing your eyes to sweep across the lens. If you detect any wiggle in the line, then the lens may have an optical defect and you should choose another pair.
Sunglass lens materials are designed and manufactured to meet the requirements of ANSI standards for UV absorption, flammability and impact resistance. Glass lenses are the most optically stable and scratch resistant lens material but they are also heavier and more expensive. Conversely, plastic lenses are the lightest and least expensive, and some are coated to increase scratch resistance. Polycarbonate lenses are the most impact resistant. Laminated lenses are combinations of glass and/or plastic to achieve a specific performance.
Sunglasses are required by federal law to be impact resistant, but they are not shatterproof nor are they an unbreakable shield to be used for impact protective eyewear used in high-risk impact sports or for industrial safety uses. Also, sunglasses are not intended for use as protection against artificial light sources, such as sun lamps, lasers, etc. Never stare directly at the sun or at an eclipse with or without sunglasses.
Frames should fit comfortably and allow the lens to be positioned directly in front of the eye. For fishermen, the wraparound style is popular and serves a function beyond style. Wraparound frames, and frames that have inset lenses in the side, prevent eyestrain from spurious light entering from the side of your glasses. In addition to the wraparound protection from extraneous light, the curved lenses sheet off moisture during brisk boat rides and although not safety glasses, they can be effective for deflecting lightweight airborne debris such as dirt and flotsam that builds up on a boat deck.
Ultraviolet Radiation (UV) consists of the short, invisible rays emitted by the sun, that travel to the earth’s surface. These rays measure between 200 and 380 nanometers or one millionth of a millimeter. There are three bands of UV, (UVA, UVB and UVC) but only two are of any concern, UVA and UVB. UVC rays are the most detrimental, but UVC rays are absorbed by ozone in the upper atmosphere and do not reach the earth’s surface. Therefore, UVC rays are not relevant to sunglass performance or of any current health concern.
UVA rays measure from 315 to 380nm and are responsible for your tan.
UVB rays are responsible for damage to tissues such as corneas and skin when you forget to use a sunscreen. Grass or dark objects reflect about 1% of UV rays, sand, 10%, water, 20% and snow a whopping 80%. Environmental UVB in concert with cold wind and micro crystals of snow has the potential to cause photokeratitis, (inflammation of the cornea) commonly know as snow blindness. While a rare occurrence, it is quite painful, but temporary disorder of the cornea. Generally, Photokeratitis symptoms will dissipate within 12 to 48 hours.
Medical experts generally agree that there are many factors that might be associated with the gradual clouding of the lens of the eye know as cataracts. Although not all scientists agree, there is some research that suggests an association with daily exposure to UVB in very bright sunlight over a period of many years. Other factors that are thought to have a causal relationship with cataracts are age, gender, ethnic origin, genetic factors, smoking, nutrition, use of alcohol, microwave radiation, and diabetes. UVA rays are mostly absorbed within the lens of the human eye. While there are no documented disorders of the human eye from UVA, it remains a much studied and debated topic.
As a result, sunglass standards place limits on UVB and UVA for sunglass lenses. Pick glasses with the highest rating possible for UV blocking capabilities, 100%, to be sure that you are adequately protected.
Conventional sunglasses reduce visible light but provide little protection against glare. Polarizing lenses selectively absorb horizontally reflected glare from surfaces such as water or roadways to improve visibility. Polarization has nothing to do with blocking UV rays, but most polarized lenses contain UV-blocking chemicals. Because they cut glare, polarizing lenses are very popular with fishermen. Polarized lenses enable you to see beneath the surface of clean water as well as reducing glare. Polarized filters are added to glass lenses by a special lamination process. Hard-resin and high-index plastic lenses are polarized during molding and on polycarbonate lenses, polarizing films are added while they are still in liquid form.
Once you’ve selected a pair of sunglasses, some simple steps will help you care for them properly. When your glasses become soiled and dusty, wash off loose grime with water before using a clean, soft cloth to wipe the lenses. When you wipe dust off with a cloth, or as is often the case, a shirttail, particles can scratch the lenses; and everyone knows how much strain scratches create. The optimal choice would be to use lens-cleaning liquid, but failing that, clear water is better than nothing.
Keep your glasses in a protective case or bag and don’t leave them on the dash of your vehicle in the summer heat when you go inside or you’ll find them turned into a pretzel and be shopping again. Worse yet, you could have to spend a day on the water without protection.