Debunking Myths About UV Light

Research demonstrates that ocular protection against ultraviolet radiation should be a concern all year long.

By Cristina Schnider, OD

Many people think they are being diligent about avoiding the sun during peak hours in the summer months, wearing sunglasses in bright sunlight, and slathering on sunscreen at the beach or pool. While these are all good ideas, practicing these steps might lead people to a false sense of security, at least when it comes to their eyes.

The reality is that the eyes are exposed to ultraviolet (UV) radiation all year long. During certain months, that exposure peaks at unexpected hours, such as early morning, when many people think it is safe to be outdoors without sun protection.

UV radiation from the sun is divided into three wavelength bands: UVA (315-400 nm), UVB (280-315 nm), and UVC (100–280 nm). The atmosphere’s ozone layer absorbs all UVC rays and about 90% of UVB rays, but most UVA rays reach the earth’s surface unabsorbed.

UV radiation is a major factor in the development of skin cancer, the most common form of cancer in the United States. UVA radiation contributes to skin aging and wrinkles. UVB plays an important role in production of vitamin D through skin absorption, but too much UVB exposure has damaging effects, including sunburn. Both UVA and UVB can cause cellular damage leading to programmed cell death, or apoptosis.1

In addition to sunlight, tanning beds, sun lamps, and arc welding also expose people to UV radiation.

Surface reflection of UV light, called albedo, is another important and underappreciated source of UV exposure. Certain highly reflective surfaces, such as snow and sea foam, can reflect up to 90% and 25% of UVB, respectively, potentially increasing total UV radiation exposure.2

THE OCULAR IMPACT

Acute ocular effects of UV exposure include photokeratopathy. Long-term, low-level UV exposure is one of the risk factors associated with climatic droplet keratopathy, cortical cataract, and other conditions. Total UV exposure varies based on a number of factors, including altitude, cloud cover, and how much time one spends outdoors.

The pattern of ocular UV exposure is not as intuitive as overall UV exposure. In part, this is because the eyes have some built-in protection against sunlight. The pupils constrict in bright light, reducing transmission of UV radiation. Squinting when looking at bright light further reduces exposure. Finally, the facial bones provide significant protection. Overall UV peaks when the sun is directly overhead (ie, between 10:00 am and 2:00 pm in the summer), but, in this position, the brow naturally shields the eyes (Figure 1). The facial structure provides less protection against light coming from below (eg, albedo) or from the sun at lower angles in the sky.

In a study of the effects of solar angle, mannequin heads with Asian facial features were fitted with UVB sensors to measure UV exposure to the face, eyes, and top of the head.3 The mannequins were positioned to mimic the slight (15°) downward gaze of an averageheight (5’5”) woman walking, with one mannequin facing the sun and the other turned away.

UVB readings were recorded once per second from sunrise to sunset on 2 days: September 21 and November 21, 2006. The study was conducted in Japan, at a latitude similar to that of Las Vegas, Nevada. Peak solar angles on those days were 54.2° and 33.6°, respectively.

The sensors on the top of the head recorded the highest UVB around noon on both days, when the sun was at its highest point. The ocular sensors told a different story, at least on September 21. On that day, the maximum UVB exposure to the eyes occurred at a lower solar angle of about 40°, which occurred at 9:00 am and from 2:00 to 3:00 pm. Total UVB in the supposedly “nonpeak” hours (8:00-10:00 am and 2:00- 4:00 pm) was nearly double the UVB exposure from 10:00 am to 2:00 pm. In November, when the sun rises to a lower maximum angle, maximum UVB exposure occurred closer to noon. However, the total ocular UVB exposure on November 21 was only 8% lower than it had been on September 21.

In part, this is because UV exposure is not as closely associated with hot and sunny conditions as we tend to think. There can be significant UV exposure even on a cool day, and certainly on a cloudy one. Up to 80% of UVA rays can penetrate clouds.4

In other words, ocular UV exposure is significant all year long and throughout the daylight hours, not just during the times when we tend to think of protecting our eyes.

UV PROTECTION

Eye care providers should encourage their patients to protect their eyes from UV exposure by employing as many protective behaviors and layers as possible. These may include seeking shade; wearing a wide-brimmed hat and well-designed and fitted, high-quality UV-blocking sunglasses; and, if indicated, UV-blocking contact lenses. Building these habits in children is especially important. Because the young lens transmits significant amounts of UV light, the greatest potential for UV exposure to the retina occurs before 25 years of age.5 But at every age, limiting ocular exposure of the eye to UV radiation is a good idea.

Sunglasses, widely regarded as an obvious means of ocular protection, have some potentially significant gaps as standalone options, however. In mannequin demonstrations, we have used specially coated eye inserts that fluoresce in response to UV light to test how different combinations of sunglasses and contact lenses protect against UV radiation from a variety of angles. These tests demonstrate that UV light often enters the eye from around sunglass frames. In particular, many styles do a poor job of protecting the eye from sunlight entering from the side or light reflecting up from a surface below, such as sand, water, or pavement. Wraparound sunglasses that fit close to the face provide more effective UV protection than other styles (Figure 2), but even these styles fall down in their ability to block UV radiation when worn even a short distance from the bridge of the nose. Hats provide good protection against UV light from higher angles, but not from rays reflected up from the ground.

And, of course, sunglasses and hats are of no use if they are not worn. We know that compliance with sun-protection measures, while growing, is still lacking. According to the Centers for Disease Control and Prevention, 58% of adults report practicing at least some sun-protective behaviors (sunscreen, sunprotective clothing, or seeking shade).6 The rates are much lower for high school students. Students are also more likely to have used a tanning bed in the past year (13.3%) than to routinely apply sunscreen (10.8%).7 In another study that looked specifically at sunglass wear, 41.6% of adults, but only 12.3% of children at parks, swimming pools, and beaches in Honolulu, Hawaii, were observed to be wearing sunglasses on sunny days.8

Because of this, an “always-on” method in the form of UV-blocking contact lenses offers an additional layer of protection. UV-blocking contact lenses are not a substitute for sunglasses, but, because they typically cover the cornea completely, they can help reduce direct and indirect exposure to UV radiation that may not have been blocked by other protective measures (Figure 3).

Not all contact lenses offer UV protection, and, of those that do, not all provide similar absorption levels. Vistakon (Johnson & Johnson Vision Care) is the only major contact lens company to provide recognized levels of UV blocking across its entire range of products. All Acuvue (Johnson & Johnson Vision Care) contact lenses block at least 97% of UVB and 81% of UVA rays. Acuvue silicone hydrogel lenses are also the only lenses in the industry that meet the Class 1 blocking standard, which requires blocking more than 99% of UVB and 90% of UVA rays.9,10

We do not yet know what effect UV-blocking contact lenses may have on long-term ocular health. In animal studies, such lenses have been shown to protect the cornea from histologic changes, neovascularization, and edema after short-term intense exposure to UV light, 11,12 and to protect the aqueous humor and lens in rabbit eyes.12,13 However, no human clinical studies have been done to demonstrate that wearing UV-blocking contact lenses directly reduces the risk of any specific eye disease or condition.

TALKING TO PATIENTS

It is important for eye care providers to make patients aware that UV exposure—which they already know can be harmful to their skin—can also affect the eyes.

A new iPad application, available at the Apple App Store from The Vision Care Institute, makes it easy to show patients the cumulative effects of UV rays on the eyes, the impact of solar angle and albedo on total ocular exposure, and steps they can take to help protect protect eyes from UV radiation, including UV-blocking contact lenses, a wide-brimmed hat and well-fitting sunglasses.

Another patient education resource is “The Sun & Your Eyes: What You Need to Know,” available in the Educational Resources section of www.acuvueprofessional.com. Printed copies (50 sheets per tear pad) are also available by request by sending an e-mail to SunandYourEyes@rprmc.com. Make sure to include your name and mailing address with requests.

As I talk to clinicians around the country who routinely integrate information about UV into their ocular health conversations with patients, they tell me that this message resonates with patients. Once patients understand that UV radiation can have potential negative health and vision effects in their eyes, they are more inclined to take steps to help protect their eyes and the eyes of their children.

This message also gives clinicians another opportunity to focus the conversation during the exam on eye health. Ultimately, by helping patients choose proper eyewear to complement their UV protection strategy, we can help lessen the risks of ocular UV exposure and protect the long-term eye health of our patients and their families.

Cristina Schnider, OD, is senior director of professional communications for Johnson & Johnson Vision Care, Inc. Dr. Schnider may be reached at CSchnide@its.jnj.com.

  1. Chandler H. Ultraviolet absorption by contact lenses and the significance on the ocular anterior segment. Eye Contact Lens. 2011;37(4):259-266.
  2. Oliva MS, Taylor H. Ultraviolet radiation and the eye. Int Ophthalmol Clin. 2005;45:1-17.
  3. Sasaki H, Sakamoto Y, Schnider C, et al. UV-B exposure to the eye depending on solar altitude. Eye Contact Lens. 2011;37(4):191-195.
  4. Parisi AV, Downs N, Turner J. Evaluation of the cloudy sky solar UVA radiation exposures. J Photochem Photobiol B. 2014;138:141-145.
  5. van Kuijk FJGM. Effects of ultraviolet light on the eye: role of protective glasses.Environ Health Perspect. 1991;96:177-184.
  6. National Cancer Institute. Cancer trends progress report—2009/2010 update: Sun protection. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services. http://progressreport.cancer.gov/doc_detail.asp?pid=1&did=2009&chid=91&coid=911&mid=#trends. Accessed July 21, 2014.
  7. Eaton DK, Kann L, Kinchen S, et al. Youth risk behavior surveillance-United States, 2011. MMWR Surveillance Summaries. 2012;61(4):1-162. http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6104a1. Accessed July 21, 2014.
  8. Maddock JE, O’Riordan DL, Lee T, et al. Use of sunglasses in public outdoor recreation settings in Honolulu, Hawaii. Optom Vis Sci. 2009;86(2):165-166.
  9. Moore L, Ferreira JT. Ultraviolet (UV) transmittance characteristics of dialy disposable and silicone hydrogel contact lenses. Cont Lens Anterior Eye 2006;29:115-22.
  10. Walsh JE, Koehler LV, Fleming DP, Bergmanson JPG. Novel method for determining hydrogel and silicone hydrogel contact lens transmission curves and their spatially specific ultraviolet radiation protection factors. Eye Contact Lens 2007;33(2):58-64.
  11. Giblin FJ, Lin LR, Leverenz VR, Dang L. A class I (senofilcon A) soft contact lens prevents UVB-induced ocular effects, including cataract, in the rabbit in vivo. Invest Ophthalmol Vis Sci. 2011;52(6):3667-3675.
  12. Chandler H, Reuter KS, Sinnott LT, Nichols JJ. Prevention of UV-induced damage to the anterior segment using class I UV-absorbing hydrogel contact lenses. Invest Ophthalmol Vis Sci. 2010;51:172-178.
  13. Giblin FJ, Lin LR, Simpanya MF, et al. A class I UV-blocking (senofilcon A) soft contact lens prevents UVA-induced yellow fluorescence and NADH loss in the rabbit lens nucleus in vivo. Exp Eye Res. 2012;102:17-27.