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2020 CE - Searching for the Ideal Progressive Lens

How to Protect Patients From Harmful Sunlight

By Carol Dykas, L.O., ABOC, NCLC
Adjunct Faculty, Middlesex Community College

Issue Date: June 2004
Expiration Date: June 30, 2007
This course is approved for one (1) hour of continuing education credit by the
American Board of Opticianry (ABO). Course # SWP135-1
Learning Objectives:
Upon completion of this program, the participant should be able to:
  1. Describe UV light and HEV (blue) light.
  2. Explain which lens offers the best protection against UV and HEV (blue) light.
  3. Describe melanin and how it protects our skin and eyes.


As the hot days of summer approach, the shelves of the department stores begin to fill with shorts, swimsuits and tank tops. The local toy stores are filling their displays with beach toys and the pharmacies are stocking their shelves with a wide range of sun-block products. But how prepared is the average optical shop to provide for the protective needs of their customers? What products do they offer to provide their patients with adequate protection from the ravages of the sun? The light we see and the light we do not can have damaging effects on the eye and the ocular adnexa and optical dispensers need to be prepared to discuss and provide it.

At the beach, sunbathers can apply sun block and many people wear sunglasses. But do they know why? For the optician, there is much more to know and communicate to patients about protecting the eyes from light, visible and invisible, than just dispensing sunwear.

  • What is ultraviolet radiation and how does it threaten vision?
  • What is the risk of exposure to high-energy visible light?
  • Which patients are at greater than average risk?
  • What are the best ways to protect our patients?

UV RADIATION

First, what is ultraviolet (UV) raidation? Light travels through space in the form of waves at different wavelengths. UV waves have a great amount of radiant energy and are not part of the visible light spectrum. UV radiation is a part of the electromagnetic spectrum found between X-Rays (10 to 190nm) and Visible Light (380 to 780nm). Some insects can see ultraviolet light, but UV wavelengths are too short for the human eye to detect.

The UV portion of the electromagnetic spectrum exists between 100 to 380 nanometers. This portion has been subdivided into three separate bands: UV-A (315 to 380nm); UV-B (280 to 315nm); UV-C (190 to 280nm) and UV-V (100-190nm).

UV-A has the lowest energy level but it is still of concern to eyecare professionals. Most professional tanning salons use UV-A lamps on their customers. UV-B, on the other hand, is recognized as a harmful, destructive form of UV light because it causes skin cancer as well as sunburn. UV-C light, with a shorter wavelength and greater energy, is potentially even more dangerous to humans, but most of the sun's UV-C is blocked by the ozone layer in the atmosphere. In industrial and medical applications, UV-C lamps are used to kill bacteria in water and purify air.

UV radiation can reach the eye directly or indirectly. Sunlight reflected off the surface of water, sand, snow or other bright objects relects UV radiation to the eyes. Also, cloudy days are not safe times from UV because the amount of UV transmitted is still significant when the sky is overcast; up to about 80 percent of its normal intensity. Many people do not think to wear UV protective lenses on these days even when they are out of doors for long periods of time.

Exposure to both UV-A and UV-B has been known to contribute to eye disease, including cataracts, macula edema and age related macula degeneration (AMD). Cataracts are a 'clouding' of the normally clear crystalline lens inside of the eye. The crystalline lens is especially at risk from overexposure of UV-A because it provides protection to the retina by absorbing the UVA. A healthy lens allows visible light to reach the retina. As the lens absorbs UVA over its lifetime, it turns yellow and reduces the light that gets through. Cataracts reduce vision by creating a 'flare' which scatters incoming light. (This condition gets its name from its resemblance on a microscopic level to a waterfall or cataract.) To the sufferer, a cataract causes various disturbances of vision, including a halo effect around lights and a general cloudiness that reduces visual acuity. A patient's genetics is a factor in whether he or she will get cataracts, but overexposure to UV radiation, now suspected as a primary cause.

Other disorders are related to overexposure to UV radiation. The epithelial and endothelial cells of the cornea are vulnerable to UV damage, which can lead to photokeratitis, sometimes described as "snow blindness" or "welder's flash," a condition which comes from brief, yet intense, exposure to UV-B light. This condition produces sunburn of the cornea; light sensitivity, tearing and corneal pain as symptoms. If limited to the top corneal layers and because the cornea repairs itself quickly, photokeratitis will heal.

Pterygium, a raised, whitish, wedge of fibrovascular tissue, invades the cornea and can affect vision. It starts within the interpalpebral conjunctiva as a pingueculae and extends into the cornea and may require surgery. Pterygia have been directly linked to overexposure of UV radiation and are more common among patients who live in warmer climates or those who spend a great deal of time out of doors. Most patients remain fairly asymptomatic, while some may complain of a foreign body sensation. In worse cases, pterygium may become red and inflamed. As the pterygium increases in size and the symptoms get worse, or vision is impaired, the chances of surgery to remove the pterygium becomes more likely.

UV radiation also causes damage to the delicate skin surrounding the eyes, ranging from premature wrinkling to cancer. In fact, about 10 percent of all skin cancer occurs on the sensitive eyelids.

HIGH ENERGY VISIBLE LIGHT

Overexposure to UV radiation is not the only threat to vision. Light that falls within the visible spectrum has been shown to cause eye damage. High Energy Visible light (HEV), which is in the violet/blue band (380 to 530nm) can cause damage to the eyes as well. Most people are somewhat aware of the UV threat to their skin, some to their vision, but very few realize the harm from HEV blue light. HEV blue light goes can damage the retina.

Extended exposure to HEV blue light, may increase the risk of developing age-related macular degeneration (AMD). Macular Degeneration is the result of photochemical damage affecting the macula, the central vision portion of the retina. It is the leading cause of blindness in persons over the age of 50. The visual effect of severe AMD can be described as looking at a clock and being able to see the numbers, but not the hands. According to a recent report, one person in six, at the age of 55, will develop AMD. That figure amounts to a potential epidemic, especially as the majority of Baby Boomers are at that age. A patient with AMD loses his or her central vision, which makes driving and many tasks we take for granted impossible. Unfortunately, this condition slowly worsens and its damage is usually irreversible.

WHEN UV PROTECTION IS MOST IMPORTANT

Because overexposure to UV and HEV light can cause significant damage to vision, even blindness, it is important to recognize who is at special risk. This includes anyone who spends extended time outside. Professional drivers and salespeople who are frequently on the road fall into that category. So do construction workers, police officers, farmers, sports fans and laborers. Laboratory workers who are exposed to UV light as part of their job are at risk, as are vacationers, who are otherwise indoors during the day, and who may be preparing to spend extended periods of time in the sun or snow. The beach, with highly reflected surf and sand all around, is a place of high exposure to UV and HEV light. And fresh snow poses an even greater risk, reflecting up to 88 percent of the light that strikes it. Geography is a factor--the closer to the equator, where the UV and HEV radiation is stronger--the greater the exposure. Altitude is a factor as well--UV radiation intensity grows by approximately 5 percent for every 1,000 feet of elevation. If, therefore, a patient is heading for a southern destination, higher altitudes, snow, etc., he or she should plan for greater eye protection.

Patients taking certain medications are also at extra risk because their medicine causes increased photosensitivity. Medicine containers often carry this very warning. It is simply another way of saying that the medicine causes an increased absorption of UV radiation. This happens because certain drugs can cause compounds to accumulate in the lens and retina, as well as in the skin, making those areas more susceptible to greater UV absorption. Some of the drugs causing heightened photosensitivity include Tetracycline, oral contraceptives, retinoids and phenothiazines. As a general rule, any patient taking medicine that increases photosensitivity should assume that such an increase applies to their eyes as well as their skin.

Contact lens wearers are at risk, too. Soft contact lenses can transmit up to 50 percent more UV light to the eye. So even if your contact lenses provide UV protection, you still need sunglasses. Contact lenses do not cover the eye completely nor the surrounding adnexa. Studies have not yet proven the effectiveness of these lenses in protecting our eyes from the harmful effects of UV radiation.

The effects of UV radiation are cumulative and the likelihood of contracting an eye malady related to overexposure increases as a person gets older and receives more and more UV and HEV radiation. As advances in medical science continue to lengthen the life span, the average person is more likely to be affected by diseases caused by increased acculmuation of the effects of UV and HEV.

And finally, children are at heightened risk. Kids may be outside for long periods of time in the sun. Certainly most children do not think much about eye protection and usually neither do their parents. With their clearer corneas and lenses, children's eyes actually admit greater levels of UV and HEV light than adults. In adults, UV light is absorbed by the lens and provides an increasingly more protective barrier to UV. This does not exist in the young eye and, as a result, can make its way to the retinas of young children, where even small amounts, accumulated over time can lead to damage. However it is alarmingly rare to see kids outside wearing sunglasses, even when their parents are wearing a pair.

While most people know that they should protect their eyes in some general way, sunglasses are usually worn primarily as a fashion statement, which means people feel that they don't need to be worn. Our task therefore, as health care providers should be to educate our patients and help them to understand that their very sight is in jeopardy. Fashion is an adjunct to healthy vision... not the other way around. This admonition applies even more so to their children.

EYE PROTECTION

What can we do to protect ourselves and our patients from this threat to our vision? The most effective solution is to alter our behavior to avoid situations where the risk is greatest. This could mean avoiding doing outdoor work or exercise when the sun is high overhead. For most of us, though, we are not in a position to make those kind of choices all the time, especially if our work takes us outside during the day.

The body offers a strong line of defense against high-energy radiation. The adult eye, for instance, becomes yellow and naturally filters some of the UV and HEV light--which is why children and young teens receive greater exposure to harmful light on the retina. Also, there is melanin. Melanin is the pigment that gives us our hair and skin color, and colors the iris in our eyes. It is also present in the retinal pigment epithelium, behind the retina. Melanin absorbs more UV radiation than HEV light and more HEV light (blue) than green, and so on, filtering the more harmful radiation in greater amounts than the less harmful light. Melanin absorbs 90 percent of the light coming into the back of the eye, preventing glare and functioning like the black paint inside a camera. Unfortunately, we lose melanin as we age. Some sunwear today replicates the absorption characteristics of melanin by incorporating material to mimic the UV and HEV absorption achieved naturally by the eye. Know the UV absorptive characteristics of the lens materials used in your office as well as UV absorption by treatements like photochromics.

SUNGLASSES, ONE OF THE BEST LINES OF DEFENSE

Sunglasses are one of our best lines of defense against damaging radiation from sunlight. Well-designed, well-fitted sunglasses are a must for anyone going out of doors during daylight hours. Eyecare specialists deal with the general misconception that sunglasses have been and remain a fashion accessory first and a preventative measure second. This dichotomy needs to be reversed.

For example, discussing and demonstrating the effectiveness of polarized sun lenses with all patients affords the opportunity to teach about the harmful effects of the sun (UV and HEV), and introduces a wonderful premium product at the same time. Polycarbonate polarized products recently introduced to the market provide the patient increased safety from injury while participating in recreational activities and protection from the harmful effects of UV and HEV light as well as protection from the distracting and potentially dangerous effects of glare.

Cheap sunglasses, referred to in a popular song, are usually a bad idea. As discussed, a significant amount of radiation comes to the eyes via reflected light. We need not look straight into the sun to be at risk. Hence, too small or ill-fitting glasses will allow a significant amount of UV and HEV light into the eyes from the periphery, defeating the very purpose of the glasses.

Wrap-around style sunglasses are not just fashion. They prevent much more harmful light from reaching the eye and its surrounding adnexa than more conventional sunglasses do. When working properly, and fitted well, the glasses block 75 percent to 90 percent visible light, 100% of the UV and can significantly reduce HEV. Quality sunglasses will be free of distortions and imperfections, which can cause fatigue and eye strain.

It is true that sunglasses can block UV and HEV light, not all sunglasses are alike. Educate patients to wear lenses that are labeled: 98 percent to 100 percent UV protection. This means a minimum of 90 percent UVA and 95 percent UVB absorption. However, do not be fooled by the color or shade of the lenses. A darker lens without the appropriate UV protection will only allow the pupil to dilate, welcoming the damaging radiation through like an open door. Amber lenses block HEV light and newly developed lenses that incorporate synthetic melanin have become available. These latter lenses reduce HEV light without significant loss in color perception.

IN CONCLUSION

As opticians, we are constantly looking for ways to better serve our patients. With the predicted increase in cataracts and macular degeneration, become part of the eyecare community's effort to enlighten the public about protection from UV and HEV radiation. Dispense quality, protective sunglasses and lenses with adequate UV protection. Help patients to understand that by taking preventative measures now they are safeguarding their and their children's eyesight for years to come.

Take a strong stance on UV protection for all patients by enacting a policy that requires the use of UV protective lenses for everyone. Certainly this is easy enough to provide. Most high-index lenses are 100% UV protective. Polycarbonate lenses provide ~100 percent UV absorption and some of the stock lens products that we use are available with UV absorbing dyes. Even those lenses that are not completely UV ansorptive can be treated in-office with UV dyes applied in your tint tank. Make a commitment to provide all of your patients with complete UV protection. It may be the most generous gift that you will give this year.



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