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With summer in full swing, many of us have plans for long days at the beach, boating on the lake, or simply getting outside and enjoying family and friends. The sun is important in our daily lives. Ultraviolet (UV) light helps regulate our sleep cycle, helps us feel good, and stimulates the body to produce vitamin D.
Although ramping up the vitamin D might not be on your (or your patients’) to-do list, making sure that your patients are aware of the implications of UV exposure and take the appropriate precautions should be your priority all year long.
Sunlight contains not only visible light, but also invisible UV and infrared light—all of which are parts of the electromagnetic spectrum. UV light can be further categorized by wavelength: UV-A wavelengths are the longest, UV-C is the shortest, and UV-B is in between. These subdivisions of UV radiation differ in their biologic activity and abundance, as well as in their ability to penetrate the skin.
UV-A light, at 315 nm to 400 nm, is not absorbed by the ozone layer and is plentiful in the atmosphere, accounting for almost 95% of UV light that reaches the earth’s surface. Although it is less intense than UV-B and UV-C, UV-A radiation is present all day, every day—even on cloudy days. This long-wavelength UV radiation reaches the deep layers of the skin and alters cells to create an immediate tanning effect.1 In fact, most tanning beds primarily emit UV-A radiation.
UV-B, at 280 nm to 315 nm, is more active than UV-A, but it is partially absorbed by the ozone layer, and its intensity levels vary daily depending on location (elevation and latitude) and time of year.1 These shallow-penetrating rays are important to the body’s vitamin D production, but excessive exposure results in skin redness and sunburn. The long-term consequences of sunburn contribute significantly to the aging process and the risk of developing skin cancer. In most parts of North America, UV-B exposure peaks in midspring through early fall, between 10:00 am and 4:00 pm<. Outside of these months, UV-B is still damaging due to its biologic activity, especially when combined with reflective surfaces such as sand, snow, ice, and water, as they increase UV-B radiation exposure.
UV-C, which contains the shortest and most potentially damaging wavelengths in the UV spectrum, is completely absorbed by the ozone layer and atmosphere.
HEALTH IMPACT OF UV LIGHT
Most people are generally aware of the effects of sun exposure, which can range from a pleasant glow to the dreaded sunburn to an increased risk of skin cancer. Patients know they should be diligent about protecting themselves against the sun’s harmful effects, but how many are aware of the ocular implications and how to properly protect themselves? The World Health Organization identified nine diseases associated with UV exposure. Among the nine, three are specific to the eye: cortical cataract, pterygium, and squamous cell carcinoma of the cornea and conjunctiva.2,3
The anatomy of the eye provides some inherent protection from the sun’s rays. The brow bone, eyebrows, eye lashes, and the globe’s position within the orbit all help to shield the eye. The pupil constricts in bright light, and the act of squinting helps to further reduce UV transmission; however, the eye and surrounding structures still receive UV exposure.
Although both UV-A and UV-B radiation can cause cellular damage leading to apoptosis, or programmed cell death,4 these two UV types can have different ocular consequences. The long wavelengths of UV-A are thought to penetrate deep into the eye, targeting and damaging the retina and resulting in conditions such a solar retinopathy, age-related macular degeneration, and uveal melanoma.5,6 The shorter UV-B wavelengths cause more significant damage and erythema to the outer structures of the eye, such as the eyelids, cornea, and conjunctiva. This damage can manifest as ptyergium, photokeratitis, photoconjunctivitis, formation of cortical and nuclear sclerotic cataracts, and basal cell carcinoma along the lower lid. Both UV-A and UV-B alter the lens.4-7
Sunshine is considered the single greatest cause of visible aging. UV exposure produces DNA damage, immunosuppression, oxidative stress, and inflammatory responses—all of which play a role in damaging, aging, and thickening the skin.6 UV-A can alter and influence collagen, contributing to wrinkles in the delicate tissues around the eyes. UV-B creates redness. Both wavelengths damage keratinocytes (basal and squamous cells) in the epidermis, the outer layer of skin, which can result in nonmelanoma tumors with a high chance of becoming cancerous.8 Basal cell carcinoma is the most common, accounting for approximately 80% of all skin cancers.3,8
Melanoma develops from damage to the melanocytes, the pigment-making cells of the skin, and it is associated with UV radiation exposure. At present, it is the most commonly diagnosed tumor type in the United States, but the incidence of all forms of skin cancer has increased over the past few decades.8 Melanomas represent less than 10% of all skin cancers, but they are responsible for most skin cancer–related deaths (75%) due to their high metastatic potential and resistance to therapy.8,9 According to the American Cancer Society, one person dies from melanoma every 54 minutes.9
PROTECTION AND PREVENTION
Everyone should be sun-conscious and practice UV avoidance, even on overcast days. Research suggests that most skin cancers could be prevented through behavioral changes alone, and campaigns aimed at changing attitudes and behavior toward UV exposure have been launched in several countries.7
Prevention awareness is especially important considering that a significant amount of UV damage is thought to occur early in life, often before the age of 25. The young human lens allows more UV transmission to the back of the eye than the adult lens.6 Basal cell carcinoma formation is also thought to depend more on the severity of UV exposure in youth, rather than a cumulative dose over a period of time.6
DISCUSSIONS WITH PATIENTS
With this knowledge, eye care practitioners should make the effort specifically to incorporate UV education during pediatric exams—for both parents and children. Over the past decade, studies and surveys have suggested a moderate increase in observance of basic sun-protective behaviors (use of sunscreen, sunglasses, protective clothing, etc.) in outdoor settings among adults. Engagement rates among high school students and children, however, remain significantly lower.10,11
It is important for everyone, regardless of age or race, to limit ocular exposure to UV light, especially with life expectancy and health care costs on the rise. Take a moment in your routine care visits to make specific recommendations to your patients regarding lifestyle and diet. Discuss the need for wide-brimmed hats and protective clothing to reduce sun exposure to the back of the head and body. Recommend prescription sunglasses that fit close to the eyes and contour to the shape of the head, shielding the face and eyes from UV in all directions.
According to the American Optometric Association, sunglasses should block more than 95% of UV-A, more than 99% of UV-B radiation, and screen out 75% to 90% of visible light to be effective.12 Even if patients use contact lenses with UV-blocking filters, they should still be using sunglasses to protect the conjunctiva and surrounding tissues.
Most sunscreens contain a mixture of chemical and physical active ingredients. The chemical ingredients form a protective film on the skin to absorb UV radiation before it penetrates the skin. The physical ingredients include insoluble particles that reflect UV away from the skin. Encourage patients in the daily and frequent use of a broad-spectrum sunscreen that blocks both UV-A and UV-B with a minimum sun protection factor (SPF) of 15. All exposed areas of the body, including the face, neck, back of the hands, and ears should be coated.
It is important to highlight that SPF does not indicate an amount of protection per se, but, rather, how long it will take for UV-B rays to redden the skin with the product in place as opposed to without. This distinction helps convey the importance of frequent reapplication of sunscreen. Finally, make sure that your patients are aware that SPF is not additive— using an SPF 15 product on top of an SPF 20 product does not create an SPF of 35. Conversely, in fact, applying a second agent before the first is dry can inactivate some of the ingredients or reduce the overall SPF.
Additionally, discussions about ocular nutrition should not be limited to macular degeneration patients. The entire patient base should be encouraged to consume fruits and vegetables containing antioxidant compounds daily.
REINFORCING THE LESSON
Some patients may be receptive to these recommendations but forget two-thirds of the information before reaching the optical shop. Developing in-office handouts for your patients can help to reiterate the need for these UV precautions and encourage good sun behavior. Eye care providers are uniquely positioned with a tremendous opportunity to highlight the importance of early UV avoidance and protection for all patients, regardless of age. It is never too late to develop potentially vision- and life-saving habits.
1. World Health Organization. Ultraviolet Radiation. http://www.who.int/uv/en/. Accessed June 19, 2017.
2. Haworth K, Chandler H. Seasonal effect on ocular sun exposure and conjunctival UV autofluorescence. Optom Vis Sci. 2017;94(2):219-228.
3. Lucas R, McMichael T, Smith W, Armstrong B. Solar ultraviolet radiation: global burden of disease from solar ultraviolet radiation. World Health Organization. 2006. http://www.who.int/uv/publications/solaradgbd/en/. Accessed June 19, 2017.
4. Chandler H. Ultraviolet absorption by contact lenses and the significance on the ocular anterior segment. Eye Contact Lens. 2011;37(4):259-266.
5. Taylor H. Ultraviolet radiation and the eye: an epidemiologic study. Trans Am Ophthalmol Soc. 1989;87:802-853.
6. Yam J, Kwok A. Ultraviolet light and ocular diseases. Int Ophthalmol. 2014;34:383-400.
7. Køster B, Søndergaard J, Nielsen JB, et al. Knowledge deficit, attitude and behavior scales association to objective measures of sun exposure and sunburn in a Danish population based sample. PLoS One. 2017;12(5):e0178190.
8. Rivas M, Rojas E, Calaf G, et al. Association between non-melanoma and melanoma skin cancer rates, vitamin D and latitude. Oncol Lett. 2017;13:3787-3792.
9. American Cancer Society. Cancer Facts and Figures 2017. http://www.cancer.org/acs/groups/content/@editorial/documents/document/acspc-048738.pdf. Accessed June 19, 2017.
10. Cancer Trends Progress Report: Sun-protective behavior. National Cancer Institute. January 2017. https://progressreport.cancer.gov/prevention/sun_protection. Accessed June 19, 2017.
11. Maddock J, 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.
12. American Optometric Association. UV Protection. https://www.aoa.org/patients-and-public/caring-for-your-vision/uv-protection?sso=y. Accessed June 19, 2017.
Rachel Grant, OD, FAAO
• assistant professor, Southern College of Optometry; optometric physician, TearWell Advanced Dry Eye Treatment Center; both in Memphis, Tenn.
• financial disclosure: none acknowledged
• 901-252-3658; firstname.lastname@example.org