Educating Patients About Ultraviolet Radiation
Most patients are unaware of the damage that ultraviolet radiation can cause to their eyes
BY STEPHEN COHEN, OD
If you're like me, you may be able to recall the days when coating yourself with oil and holding a metallic reflector under your chin was a surefire way to achieve that great summer tan. Now we know that this practice may also lead to skin damage and even cancer. Long ago, a suntan was indicative of the working class and manual labor. In the past century, however, it came to represent just the opposite — a leisurely, vacation-filled life. In spite of the fact that the sun protection product market is a $5 billion industry, damage to skin cells occurs even with careful tanning.
What about the effects of the sun on our eyes? Market research has shown that close to 90 percent of consumers are aware that ultraviolet radiation (UVR) may damage our skin, but less than 10 percent know that it may damage our eyes as well. Nine out of 10 people admit to wearing plano sunglasses sporadically, and one in four people never wear them at all.
Even though we know that UVR is damaging to our skin, all clinicians struggle to motivate patients to take preventive measures. Perhaps this is because most of the time the harmful effects of UVR are not immediate; they're delayed by years or even decades. It seems that the longer the delay between exposure and damage, the greater the difficulty in getting the message across. The effects of UVR exposure on ocular health are cumulative, and with the possible exception of solar keratitis, signs and symptoms are significantly delayed.
In this article, I will discuss recent scientific findings regarding the effects of UVR on the eyes, our obligation to help and educate our patients and the opportunity this issue can provide, particularly in relation to contact lenses.
Ocular UV and Ozone
The following discussion in this section is excerpted from the article "Ocular Ultraviolet Hazards and Global Ozone Loss," by Ernest V. Loewenstein, PhD, OD, and Max Loewenstein, PhD, which appeared in the August 1993 issue of Contact Lens Spectrum.
The strongest source of light to which most of us are exposed is the sun, whose spectrum is rich in infrared and ultraviolet, as well as visible, radiation. The earth's stratospheric ozone is the shield that protects us from the short wavelength ultraviolet, the radiation most effective in causing sunburn, skin cancer, keratitis and cataracts. In recent years, man-made chemicals released into the atmosphere have reduced the amount of ozone both on a seasonal and a permanent basis, raising the specter of increased abiotic effects from greater exposure to UV-B in sunlight.
Electromagnetic Spectrum The electromagnetic spectrum extends from less than 200nm to more than 780nm (Table 1). The eye and the skin are the only organs of the body normally exposed to light. The eye is specifically adapted to respond to a certain band of electromagnetic wavelengths known as visible light. Infrared and ultraviolet wavelengths elicit no visual response but, nevertheless, enter the eye and may produce heating and photobiological changes.
Electromagnetic waves carry energy as well as information: the structure that absorbs the light can be damaged by the energy deposited there. Ultraviolet wavelengths carry enough energy to produce free radicals that are themselves very reactive in biological systems. Shorter wavelength photons carry greater energy and, therefore, more potential for causing biological damage.
Thermal and Photochemical Effects The deposition of light energy in tissue can cause damage in two fundamentally different ways: thermal effects and photochemical effects. The former implies heating of tissue to the point of irreversible damage, a process that takes time, while the latter depends on quantum effects that occur instantaneously with the absorption of each photon. The existence of repair mechanisms tends to limit the damage in either case, but photochemical damage is more likely to be cumulative over a lifetime of low-level exposure, compared with the more episodic nature of thermal effects.
Direct, Scattered and Reflected Sunlight Light from the sun may reach the eye by direct viewing, scattering from the sky or diffuse reflection from objects, including the ground. Direct radiation is least important from the point of view of ocular hazard, as very few people look directly at the sun. The overhang of the brow is protection against direct illumination of the eyes when facing in the direction of the sun. Much more important is scattered light from both the sky and the ground.
Light reflected from the surface adds to that received directly and by scattering. Surface reflectance can be quite variable. Fresh snow reflects as much as 85 percent of the UV-B, which is why eye protection is needed when skiing. Even surfaces of lower reflectance, such as sand, can be important because the reflected radiation can reach the eye directly in spite of wearing a hat to protect from overhead sources. This is why some people tan or even burn when sitting under a beach umbrella.
Ozone Ultraviolet absorption depends principally on the amount of ozone in the stratosphere, while the midrange (visible and infrared) absorption depends upon the presence of water vapor, carbon dioxide and other trace gases plus particulate matter, all of which can vary with time and location.
Although ultraviolet comprises only a small part of the total solar radiant energy reaching the earth, its importance is enormous because of the potential for ocular and skin damage. UV-B comprises less than 2 percent of the total incident sunlight outside the atmosphere, while UV-A accounts for about 8 percent. Ozone is continuously produced high in the stratosphere by photochemical action of solar UV-C radiation in the tropics. It is carried to higher latitudes in both hemispheres by the prevailing stratospheric winds.
Ozone loss occurs naturally in the stratosphere through reaction paths involving oxides of hydrogen, nitrogen and several halogens. In recent years man-made chemicals, most notably the fully halogenated methanes (CFCs), have added to the naturally occurring chemical destruction of stratospheric ozone, resulting in a net decrease of total ozone at some latitudes. The most dramatic example is the Antarctic "ozone hole," now a persistent phenomenon observed annually since the early 1980s in the austral spring. Less dramatic but perhaps more worrisome is what appears to be a very significant 3-to-6-percent-per-decade decay, varying with latitude, since 1980 in the northern hemisphere.
Stratospheric ozone is responsible for the cutoff of solar UV in the vicinity of 290nm.
The Effects of UVR
As alluded to in the last section, UV-A, UV-B and UV-C are the three types of ultraviolet light. The wavelength of UV-C is from about 200nm to 290nm. Most of the UV-C radiation is absorbed in the atmosphere.
UV-B is from 290nm to 315nm, and its exposure increases by 10 percent for every 1,000 feet in elevation. The letter "B" in UV-B has been associated with "burn," as in sunburn. This is because DNA absorbs UV-B, and this type of radiation can cause cell damage. The amount of UV-B at ground level at the equator is about 1,000 times greater than that at the poles. Every 1 percent decrease in the ozone layer of the atmosphere results in a 2 percent increase in UV-B exposure and a 4-to-6 percent increase in carcinoma. Additionally, UV-B is implicated in conjunctival squamous cell carcinoma.
UV-A covers about 315nm to 380nm and is associated with aging of the skin as well as with increasing the damaging effects of UV-B on the eyes. UV-A may also be damaging to the retina, but most UV-A is blocked by other ocular structures. The retinal pigment absorbs between about 380nm and 780nm (visible light), and there are some suspicions that the blue end of the visible light spectrum may add to the likelihood of eye damage, especially retinal damage.
According to the World Health Organization (WHO) and the National Women's Health Resource Center (NWHRC), 80 percent of lifetime UVR exposure occurs by 18 years of age. Both reflective and direct UVR exposure may cause ocular damage. Grass and soil reflect about 10 percent of UVR; sand, 15 percent; sea foam, 25 percent; and snow, about 80 percent.
The National Weather Service (NWS), the Environmental Protection Agency (EPA) and the Centers for Disease Control and Prevention (CDC) developed the UV Index, which most of us are familiar with. It estimates the amount of UVR that will reach the earth in any given area for the next day and is listed on a scale of low (<2) to extreme (>11) (Table 2). The high-risk periods in the UV Index are between 10 a.m. and 4 p.m. It's estimated that at noon, UVR can be 10 times higher than three hours earlier or later.
Ocular Structures According to Japanese researcher Horoshi Sasaki from the Kanazawa Medical University, UV ocular exposure in the spring, summer and fall in the early morning and late afternoon — when the incidence of sunlight is at a lower angle — may actually be up to double that of the typical peak UV hours. Sasaki concluded that the eyes are still at risk to UVR damage during these times when many people don't take as many precautions as they do during other periods of the day. Because many people do not suffer from the symptoms associated with sun brightness during these off-peak hours, sunglasses and hats may be worn less. This may, however, also be the time of day that many people are involved in outdoor activities. The Sasaki study helps to demonstrate the need for a more thorough education about UV risk for our patients.
Figure 1. The only known cause of pterygium is ultraviolet radiation.
Figure 2. UV-induced ocular tumor.
For some time, patients were not made aware of long-term ocular damage caused by UVR exposure. The WHO now estimates that one in six people older than 40 has clinically significant cataracts, as do half of the people older than 80, and that 20 percent of all people are blinded by cataracts (about 16 million) due to sun exposure.
Damage may occur in all ocular structures. UVR may affect the eyelids, causing wrinkles, dermatochalasis and malignancies. In fact, melanoma on the eyelid is a fairly common location. This may occur because the eyelid skin is the thinnest in the body. Additionally, we don't typically apply sunscreen to the lids for fear that the lotion will get into our eyes. Furthermore, sunglasses are either under-utilized or do not provide coverage to an ample area of the adnexa.
Additionally, the ocular surface may develop pterygium (Figure 1), corneal and conjunctival malignancies (Figure 2), vernal catarrh, pinguecula (Figure 3) and herpetic keratitis reactivation. Uveal damage may include melanoma, miosis and uveitis; the lens may develop cataracts (Figure 4), capsular pseudoexfoliation and early presbyopia. The exact mechanism of early accommodative loss (the normal age-related development of presbyopia) is not fully understood. This change may be due to the "calcifying effect" of cataract development. With UV exposure, the vitreous may undergo liquefaction, and the retina may develop photic maculopathy, age-related macular degeneration (AMD) and choroidal melanoma. According to Minas Coroneo, MD, of the University of New South Wales, ocular changes may start as early as 9 years of age. He found that 80 percent of Australian children had signs of eye damage from UVR by age 15.
Coroneo also described what he termed the peripheral light focusing effect (PLF). The PLF effect occurs when temporal light intensifies while passing through the ocular surfaces — from the temporal cornea to the nasal part of the eye. He concluded that light is 22 times stronger on the nasal limbus and eight times stronger at the nasal lens cortex. These are the most common locations for pterygium and cortical cataracts — almost 60 percent of all cortical cataracts occur inferonasally — and both are associated with chronic UVR exposure. This exposure comes from the light that shines through the sides of sunglasses or reflects off the back surface of sunglasses into the eyes.
Currently, the only known cause of pterygium is UVR. Pterygium has an indirect effect on dry eyes due partially to goblet cell suppression and decreased corneal sensitivity beyond the leading edge of the growth. With cataracts, UVR may cause DNA alteration, and damaged soluble proteins may clump together, causing opacity. With ozone depletion and increased UVR exposure, a rise in cortical cataracts over the next few decades by up to 7 percent is expected, which may cost several billion dollars in increased medical costs.
Figure 3. Inflamed pinguecula.
Figure 4. Nuclear sclerosis cataract.
Previously, it was believed that the cornea was not a particularly strong UV filter and that most UVR absorption occurred in the epithelium, but recent studies show that the stroma is an important UVR absorber. This may be noteworthy for patients who have keratoconus and pellucid marginal degeneration (PMD), in which thinning of the cornea could result in greater UVR transmission into the eye. These suspicions could also be significant for post-LASIK and post-photorefractive keratectomy (PRK) patients because the thinner post-surgical stroma theoretically might allow more UVR to pass through to the crystalline lens, which may increase risk factors for early cataract development.
Practitioners' Obligation
The PLF effect and its implications for sunglass use present an outstanding opportunity for eyecare practitioners to educate patients. To convey the message easily to patients, consider a term that encompasses the symptoms of the condition as well as the threat of permanent damage. Dr. Paula Newsome of Charlotte, NC, suggests the term Solar Ocular Syndrome (SOS). This term could describe the collective issues and outcomes associated with ocular UVR exposure. Perhaps in time this may even be listed as an ICD-9 diagnostic code. Ultimately, an ocular UV rating system — similar to SPF — should be developed. In the meantime, we must find a way to simplify the message about UVR damage.
Eyecare practitioners are certainly aware of the need for UV protection, but rarely talk to patients about it. According to the Brand Health Monitor Report of November 2005, eight out of 10 patients wish they knew more about the impact of UVR. Similarly, 75 percent of patients worry about the impact of UVR, but two-thirds of these believe that sunglasses alone are sufficient. Also, almost 60 percent do not know that some contact lenses have UV-blocking properties, while 40 percent believe that all contact lenses provide UV protection. At the same time, 75 percent would pay more for UV-blocking contact lenses. Lastly, six out of 10 consider UV blockage to be the most desired feature of a contact lens, and 85 percent of parents of teens and pre-teens think UV protection would be important when discussing lens options for their children.
Children have larger pupils and clearer lenses, which are affected more by reflective surfaces. Children who spend a lot of time outdoors receive three times the annual UVR dose as adults. It's also estimated that while 75 percent of UVR is transmitted by the lenses of patients younger than 10, only 10 percent is transmitted by the lenses of patients older than 25 years of age. So, we must reinforce the urgency of protecting children from UVR by educating parents about preventive measures.
Nonetheless, while one school district in Australia made sunglass use compulsory for students in kindergarten through sixth grade, 65 percent of US elementary schools prohibit the use of sunglasses.
The Educational Opportunity
According to the National Eye Institute, National Institute of Health and Lions Club International Foundation, more than 70 percent of survey respondents rated loss of vision a 10 on a 10-point scale even though, as noted earlier, a small fraction of people understand the damage UVR can do to our eyes. Like our dermatology colleagues have found with UVR and the skin, beauty and appearance (brighter eyes, less redness, fewer wrinkles) may ultimately motivate patients greater than fear of possible damage. With the amount of information that we must share with patients and increasingly less time to do it, how can we simplify the message without losing the desired effect?
First let's consider the available precautions. The most common protective devices are plano sunglasses. But traditional sunglasses (non-goggle or extreme wrap-around) may block only about half of the UVR that the eye is exposed to. As a result of decreased brightness, the pupil becomes enlarged, which leads to less squinting, which causes more UVR exposure.
A simple exam room sunglass analysis can educate patients about the important qualities of sunglasses. I inform patients about eyelid melanomas, increased UV-induced cataracts (due to UV that gets around the sunglasses) and lens optics. These represent the three important features that patients should assess when purchasing sunglasses. We request that patients bring all sunglasses to their appointments, and I check them for the degree of surface area coverage, the quality of the lens optics (imaged onto a screen through a projector) and UV and visible spectrum blocking on a spectrometer. Patients have been incredibly appreciative of this information and, not surprisingly, our optical sunglass sales have increased dramatically of late. This approach doesn't take up much time and works well when practitioners present it as an educational opportunity rather than a presentation by another staff member, which may be perceived as a sale presentation.
What other precautions can we take to boost UVR protection? A hat alone provides no protection from UVR that's reflected from surfaces. But, a combination of sunglasses and a wide-brimmed hat provides an eight-fold decrease in UVR exposure. The optimal combination for protection from UVR, however, appears to be sunglasses, a hat with a wide brim and, where possible, UV-blocking contact lenses. Soft contact lenses cover the limbal stem cells, which decreases the PLF effect and the resultant risk for pterygium. The average contact lens blocks 10 percent of UV-A and 30 percent of UV-B. Some Class 2 contact lenses (Biomedics by CooperVision, Precision UV by CIBA Vision and some GP lenses) block higher amounts of UVR. A Class 2 level is achieved with greater than 70 percent UV-A and greater than 95 percent UV-B. To date, Acuvue Oasys and Acuvue Advance brands (both Vistakon) are the only lenses to provide Class 1 (more than 90 percent UV-A and 99 percent UV-B) UVR protection. Both Acuvue Oasys and Acuvue Advance brands received the American Optometric Association and the World Council of Optometry's Global Seal of Acceptance for contact lens UV-blocking.
We must also educate our patients about other potential risk factors. With the newer understanding about the effect that a thinner cornea may have on UVR transmission to the crystalline lens, we need to proactively educate our LASIK patients about the potential increased risk of cataracts and the importance of post-surgical UV protection. We also need to discuss the ocular damage that may occur from photosensitizing systemic medications, such as Accutane (isotretinoin, Hoffman-LaRoche) and tetracycline, both of which are often used by pediatric patients. By querying patients about their lifestyle, we are able to further assess risk factors (such as time spent outdoors). UVR exposure is the most significant modifiable risk factor in the development of cortical cataracts and pterygium.
SOS
As stated earlier, the most critical issue is simplification of the message. Using the acronym SOS for solar ocular syndrome can help combine the many deleterious effects of UVR exposure into one pointed lesson. The overall message must be simple. We must communicate these three succinct SOS factors to our patients:
• Ultraviolet radiation can damage the eyes.
• People must adequately protect their eyes from ultraviolet damage.
• The best combination for optimal ultraviolet protection includes sunglasses, a brimmed hat and UV-blocking contact lenses (where applicable).
To encourage patients to use optimal UV protection, we should promote beautiful, bright, healthy eyes. Also, ask patients if they are using "eye sunscreen." The resultant puzzled expressions will provide an opportunity to educate about optimal UV protection.
Bring up the issue of UV protection with all of your contact lens patients, even those who are otherwise happy with their current lenses. By doing so, you can offer your patients the option of an added feature that their current lenses may not provide, which may enhance their opinion of your services. We're often hesitant to discuss new options with contact lens patients who are otherwise satisfied with their current lenses. By not discussing other options, we miss a valuable education opportunity that not only will demonstrate that we are staying current with advances in contact lenses, but also will help to build long-term patient loyalty by showing our interest in their long-term visual welfare.
We all want our patients leaving our offices seeing better than when they came in. We should also set a goal of wanting our patients to know more than when they came in. An educated patient will more likely become loyal, refer others and respond to our recall efforts because the value of the care they received is enhanced by this education process.
Nowhere is this need more important or the opportunity greater than with younger patients. I practice in the Sun Belt, where we have up to 315 days of sunshine per year. Even on cloudy days, about 40 percent of UVR is transmitted. I discuss UV protection with all parents, and, whenever possible, I fit my younger patients with UV-blocking contact lenses. In fact, when a contact lens manufacturer's representative visits my office with a new contact lens, my first question is always, "Does the lens include UV-blocking?"
Always take the time to discuss the importance of UV protection with parents, and they will be grateful that you are looking out for the long-term health of their children. When I speak with parents of young patients, I explain to them that UV radiation may cause long-term damage to their child's eyes, just as it may to their skin. I relay to them the latest scientific findings regarding UV exposure and stress the importance of UV-blocking lenses because kids spend more time outdoors compared to adults. I try to prescribe contact lenses that block almost 100 percent of UVR, and I have yet to see a parent question the value of this feature or express anything other than appreciation.
Make sure to deliver the message about SOS to your patients. The ocular effects of UVR should be as important and widely discussed as the potential skin effects. If you explain to patients that they need to protect their eyes and then provide them with simple ways to do it, you might exceed their expectations of you as a clinician and successfully take the opportunity to deliver an important message about saving their eyes.
Conclusion
UVR can cause ocular problems, which are exacerbated by the decrease of the ozone layer and the increase of light to our planet. You should be aware of this and educate your patients about how to best protect their eyes. CLS
Dr. Cohen is in private practice in Scottsdale, Ariz. He is a past-president of the Arizona Optometric Association. He was a founding faculty member of The Vision Care Institute, and he has served as a national spokesperson concerning UV and the eyes. Dr. Cohen has also participated in numerous FDA studies and has lectured nationally and internationally.
For references, please visit www.clspectrum.com/references.asp and click on document #153.
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