Article

Understanding Sunwear Protection

A review of what you and your patients need to know about protecting the whole family's eyes

EYE PROTECTION

Understanding Sunwear Protection

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WHAT YOU AND YOUR PATIENTS NEED TO KNOW ABOUT PROTECTING THE WHOLE FAMILY’S EYES

BY JENEAN CARLTON, ABOC, NCLC

YOU’VE PROBABLY heard all the responses patients give when asked if they wear protective sunwear: “I’ve never had prescription sunwear and do just fine without it;” “I can’t afford prescription sunglasses;” and even, “Prescription sunwear is a luxury I don’t need.” However, when inquiring whether patients use sunscreen to protect their skin outdoors, most reply emphatically that they do.

Consumers associate ultraviolet (UV) radiation as damaging to skin, but not as dangerous for delicate ocular tissue and structures. The likely reason for this is that patients receive little information about the dangers UV wavelengths pose to their vision compared with the degree of information detailing the dangers of UV to their skin. Because of this, most patients aren’t aware that long-term UV light exposure is cumulative and can lead to serious ocular diseases, including blindness.

It is estimated that less than 10 percent of consumers are aware that long-term exposure to UV wavelengths can increase the risk of cataracts, age-related macular degeneration, retinal damage, cancer of the eye or eyelids, and other ocular diseases.

Roughly 23 percent of people in the U.S. never wear protective sunwear and about only six percent are aware that it is important to protect their vision with prescription sunwear, or, in the case of emmetropes and contact lens wearers, quality non-prescription sunwear.

As eyecare professionals, it’s essential that we educate patients about the hazards of UV radiation to their eyes, and it is especially vital to educate parents about the threat it poses to children’s vision since cumulative UV light exposure is linked to so many vision-threatening ocular diseases.

UV SPECTRUM

The UV spectrum is part of the Electromagnetic Spectrum (EM), an arrangement of all known radiant energy—from radio waves, which have low frequencies, low energy, and longer wavelengths, to higher energy gamma rays that, as a result of having shorter wavelengths and higher frequencies, produce dangerous levels of energy.

Visible light falls between 380-760 nanometers, and UV wavelengths between 100-380 nm. The shorter wavelengths of the EM spectrum cause the most dangerous levels of energy, and the UV spectrum consists of short wavelengths.

It is divided into three sections, from longer to shorter wavelengths: UVA, UVB, and UVC.

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IMAGE COURTESY OF TRANSITIONS OPTICAL, INC.

UVA consists of wavelengths from 315-380 nm. It is this range of the UV spectrum that causes tanning. Photochromic lenses change from their clear, inactivated state to their darkened state because the dye formations used in these lenses are activated by wavelengths in the UVA range.

UVB wavelengths are from 280-315 nm and are the most damaging to human tissue, including the eye. This range causes sunburn and is linked to many types of skin cancers, including melanoma.

UVC wavelengths range from 100-280 nm and are harmful to skin and ocular structures and tissue. However, the majority of these wavelengths are absorbed by the ozone layer of the atmosphere and don’t reach the earth’s surface.

Material Matters
Some materials, such as polycarbonate and super-high index, aren’t as easy to tint as other materials and can’t be darkened to a #3 level depth of color. This is due to the molecular makeup of the material itself—it isn’t porous enough to readily absorb the dyes. When tinting polycarbonate lenses, it is actually the scratch-resistant coating that absorbs the color, not the lens material.

EARLY PROTECTION

Whether they need corrective eyewear or not, children of all ages should weary ophthalmic sunwear that provides 100 percent protection from UVA and UVB wavelengths. Children spend much more time outdoors than adults and thus have much greater exposure to UV wavelengths than most adults. Because of this, it’s important to begin protecting children’s eyes at an early age.

The crystalline lens inside an adult’s eye is mature and better able to filter, to some degree, UV rays. The lens inside a child’s eye, however, isn’t able to do so, and damaging UV radiation can easily reach the retina.

Because the cumulative effects of UV wavelengths can lead to ocular diseases later in life, it’s never too early to protect children’s eyes.

Talk with parents about the dangers of UV light and the importance of protecting children’s vision early on with quality ophthalmic sunwear. Remind parents that toy sunglasses don’t offer UV radiation protection and could even cause eye damage if fabricated with lenses that aren’t shatter resistant.

Children requiring corrective lenses should wear polycarbonate or Trivex for safety reasons. The added benefit is that both materials absorb essentially 100 percent of UV wavelengths. Therefore, it isn’t necessary to offer a UV filter with either Trivex or polycarbonate lenses. As for tinting, absorptive dyes will tint the polycarbonate lenses to at least a #2 depth of color.

Photochromic lenses are another good option for children needing prescription sunwear. They offer protection from UV wavelengths and also darken when exposed to UV light.

Frames that come with a magnetic sun clip are good options for children because these clips are less likely to get lost and damaged while kids play. They often include a polarizing filter, offering children comfort and glare protection.

If parents make it a point to consistently wear sunwear when outdoors, their children will be more apt to get into the habit of doing so as well. Children should be armed with UV light protective sunglasses (and sports goggles). On sunny or cloudy days, UVA and UVB protective sunwear is a must because wavelengths in these ranges penetrate the atmosphere.

Back-Surface Reflections

Lenses that block 100 percent of UVA and UVB wavelengths, including polarized, photochromics, and absorptive tinted lenses, block these damaging rays from transmitting through the front of the lenses.

With all sunwear, UV light damage can occur to the eye as a result of to light being reflected from the back surface of a lens. Adding an anti-reflective coating to the back surface of sunwear lenses prevents UV radiation from being reflected into the eye from the backside, thus further protecting patients from ocular damage caused by UV light.

SUNWEAR LENSES

Absorptive tints are heated liquid dyes that are absorbed into the lens material. These dyes are fixed tints and cut down brightness by reducing the amount of light transmitted through lenses.

Lenses are immersed into the heated dyes, which are available in numerous colors for sunwear or fashion uses, and can also be applied in various ways. The lenses can be completely tinted or a gradient method of tinting can be applied, leaving the top of the lens darker than the bottom. Some patients prefer a double-gradient tint where one color is tinted at the top of the lens and another color is tinted on the bottom.

With absorptive tints, the saturation level of the tint depends on the amount of time the lenses remain in the heated dye solution as well as the porosity of the lens material being used. Most resin lens materials, such as CR-39, will readily absorb dyes. Therefore, the lenses easily achieve a #3 level depth of color, which is the usual depth of color for sunwear.

Dark sunglasses at a #3 level tint, in either gray or brown, will transmit approximately eight to 18 percent of light through the lenses, while lenses darkened to a #2 level saturation of gray or brown will transmit about 18 to 43 percent of light. This means that the tint on these lenses is lighter than those tinted to a #3 depth of color.

Most patients in the U.S. prefer sunglasses with a #3 level gray tint that allows wearers to see colors as they naturally appear. Other popular lens colors in the U.S. are brown and G-15, a gray/green combination made popular by Ray-Ban sunglasses.

Regardless of the lens color choice, most patients prefer a #3 level dark tint for sunwear. However, seniors often prefer a #2 depth of color—possibly because of cataract development or needing additional light transmission because of the natural aging of the crystalline lens. Sunwear options include polarized and photochromic lenses.

Polarized lenses eliminate glare by having an aligned polarizing filter that allows the passage of light rays in one direction, while blocking light traveling in other directions. Polarized sunwear is preferred for water sports because the lenses block horizontally reflected light waves. Drivers also enjoy these lenses because glare from vehicles and the road is eliminated.

Photochromics are variable tinted lenses that are activated by UV wavelengths. When activated, the dye molecules change their shape and molecular structure. This in turn causes the lenses to change to a darkened color. The dye molecules revert back to their original structure and formation, and to the leuco or clear state, when the UV radiation is removed.

Vehicles are equipped with windshields and side windows which include UV filters, so photochromics won’t darken as much inside a vehicle as they do outdoors. One way to solve this problem for patients is to offer a sunglass clip to wear over prescription lenses while driving.

Whatever their lens choice, the best way to protect patients from ocular diseases associated with UV light exposure is to educate them about the importance of protecting their vision, as well as their children’s vision, with ophthalmic quality sunwear that blocks 100 percent of UVA and UVB wavelengths. images