The benefits and disadvantages of UV light
Why is it important? What are the risks?
Intense UV radiation can damage the skin and eyes – that much we know. Yet our bodies simply can’t do without UV light, and we benefit from it in a number of different ways. BETTER VISION explains: What are the different types of UV light? What are the upsides and downsides of UV light? How do we benefit from it? How can it hurt us?
The benefits of UV light
Summer means fun in the sun! For many people, this is the best time of year. They head out to enjoy the great weather, spending time at sidewalk cafés, parks and pools. When people mention UV light, they often only talk about its damaging qualities – but we benefit from UV radiation in different ways. UV light impacts numerous metabolic processes in people, plants and animals. But our digital way of life means we’re spending more time indoors and thus don’t see the daylight all that much. So it’s even more important to step outside more often and take part in outdoor activities to make ourselves feel good and stay healthy. All the same, we should ensure that we are sufficiently protected from the sun – that applies to our skin as much as it does to our eyes. To ensure you’re fully protected, we recommend wearing either a high-quality pair of sunglasses or clear lenses with an integrated UV filter up to 400 nm.1 That’s because UV radiation can damage our eyes in a number of ways – but there are great ways to protect ourselves, too.
The downsides of UV light
Spending a lot of time in the sun means intense radiation – this can damage your skin and eyes if you don’t protect them from the sun and wear good sunglasses with UV protection. Chronic eye damage caused by UV radiation cannot be treated. But what exactly are the negative effects of UV light on our eyes and skin?
Eye damage caused by UV light
When people think of sun protection, the first thing that springs to mind is their skin. But our eyes are also sensitive to UV radiation – not only when the sun is shining but in the shade, too. Not only at noon, but all day, every day. Even on a cloudy day, UV radiation can be as high as 70 to 75 percent on the ground due to reflection and dispersion.2 Water, for instance, reflects up to 20 percent of UV radiation, fresh snow roughly 88 percent, sand up to 25 percent and a concrete road around 12 percent.3
In terms of UV protection, the earlier you start, the better – but then again, it’s never too late to start!
Children’s eyes are particularly sensitive to UV rays. By the time we turn 20, we’ve already been exposed to around half the amount of the UV radiation a 60-year-old has been exposed to. In other words, by the time we turn 20, we’ll have absorbed around as much UV radiation as we would between the ages of 20 and 60!4
If we don’t protect ourselves, we could end up damaging our eyelids and the skin around our eyes, or even develop one of many other diseases, such as those affecting the cornea. These include conjunctivitis and photokeratitis (a.k.a. ultraviolet keratitis). These terms refer to damage to the cornea caused by strong UV radiation that you find up in the mountains. In continuous intense light, we run the risk of the eye’s lens becoming cloudy, which can lead to premature cataract. UV radiation is also suspected of causing tumours on the eyelid.
In order to effectively protect both the eyes and the surrounding skin from UV radiation, we recommend wearing both sunglasses and normal, clear lenses with full UV protection up to 400 nm. This way, you’ll be protected whatever the weather – even on cloudy days.
Here’s a tip for contact lens wearers: while contact lenses with UV protection are available, they don’t protect your sensitive eyelids, particularly the edges. That’s why we recommend you invest in a good pair of sunglasses capable of blocking incident light.
Damaging effects of UV light on your skin
UV radiation can also damage our skin. We know that excessive tanning outdoors and spending too much time on the tanning bed are responsible for the increased rate of skin cancer. UV exposure is therefore the main cause of skin cancer. A major risk is that the eyes are not normally taken into account when people think about sun protection. In fact, 5–10 percent of all skin cancer cases involve the eyes.5 To ensure that this sensitive area is protected from UV radiation, we recommend wearing both sunglasses and normal glasses with full UV protection up to 400 nm. This will also protect the area around the eyes against premature photoaging, which is caused primarily by UV radiation. Common long-term effects of excessive tanning are expanded pores and blood vessels, damage to the connective tissue, blackheads and dry skin. In addition to sunburn and redness, UV light can cause a variety of symptoms that are often collectively referred to as a “sun allergy”. However, there is no such thing as a sun or light allergy in medicine. Instead, what people are referring to are certain symptoms rather than an actual allergy. Illnesses that people frequently call a sun allergy can generally be traced back to sunlight, and to the UV portion of light in particular. For example, a widespread illness caused by UV radiation is polymorphic light eruption, also known as sun eczema. Symptoms typically become evident when we expose our skin to a large amount of sunlight, such as on the first long walk we take when spring arrives. Extremely itchy reddening, blisters or nodules form on the areas affected. Depending on the person’s skin, the severity of the symptoms can vary enormously. Taking certain medications in connection with UV radiation can even elicit a reaction that seems like an allergy. In medical jargon, this illness is known as phototoxic or photoallergic photodermatitis.
Acne aestivalis frequently comes up in connection with the damage caused by UV light. The skin suddenly forms itchy red patches, flecks on the skin, blisters and nodules. The term “acne” is actually misleading, since this isn’t a textbook case of acne – just the symptoms are similar. This reaction is actually a unique form of sun eczema. Acne aestivalis is not only caused by intense UVA radiation, but primarily by an allergic reaction to sunscreen. While the exact cause is unknown, we do know that the effect of UV radiation on greasy sunscreen can cause the skin’s oil glands to become inflamed. This reaction will lead to the aforementioned symptoms.
Tip: In some cases you can prevent Acne aestivalis by using special sunscreen (available at specialist retailers) that soothes sensitive skin when applied regularly.
When enjoying the sunshine at the beach, make sure you protect your eyes by wearing high-quality sunglasses with a UV filter up to 400 nm and regularly apply enough sunscreen to prevent radiation damage. ZEISS PhotoFusion self-tinting lenses feature complete UV protection up to 400 nm.
What exactly is UV light? Where does it come from?
The biggest source of UV radiation on Earth comes from the sun. People usually refer to it as “UV light.” In physics terms, however, this is incorrect as it’s not light per se, but in fact radiation. While light and radiation are both made up of electromagnetic waves and are part of what’s known as the electromagnetic spectrum, where all kinds of these wavelengths are brought together, there is a difference between the two: light is something we are capable of perceiving. “Radiation” is the invisible part of the wavelength spectrum that includes infrared, X-ray, microwaves and UV rays.
The different types of UV light
There are different types of UV rays, and each one affects the body in a different way. A distinction is made between UV-A, UV-B and UV-C radiation.
(100 to 280 nm) barely penetrates our skin and retina, but a large dose can still cause red skin and painful eye inflammation. UVC radiation also destroys cells, which is why it is used in artificial disinfectants. Yet even if UV-C radiation were to cause damage, you don’t need to take any special precautions because the ozone layer absorbs it completely – even in those areas where the ozone layer has been damaged.
UV-A radiation/UV-B radiation
UV-A radiation (315 to 400 nm) and UV-B radiation (280 and 315 nm) have a similar effect on the body. They can trigger acute medium- and long-term damage:
Enjoyed in moderation, UV-A and UV-B rays tan the skin, but high doses can cause redness, rashes, allergies or sunburn, for instance on the eyelids. UV-B radiation can cause acute photokeratitis (a.k.a. UV keratitis), a type of damage to the cornea.
UV radiation may lead to conjunctivitis.
UVA radiation can speed up skin aging (or photoaging) and weaken our ability to see. It increases the risk of early-onset age-related macular degeneration (AMD). UVA radiation is also suspected of causing cancer of the eyelid, triggering dangerous changes to the cornea and it can even lead to cataract. 48 percent of all cases of blindness around the world are caused by cataract – and in around 20 percent, UV radiation is responsible for causing or exacerbating the disease. There are also indicators that UVA and UVB radiation could be partially responsible for melanoma. Tissue growth on the conjunctiva and at the edge of the cornea (e.g. Pterygium conjunctivae) and Pinguecula are typical symptoms of excessive UV exposure.
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UVA radiation can reach up to 400 nm; International Commission on Non-Ionizing Radiation Protection (ICNIRP), American Conference of Governmental and Industrial Hygienists (ACGIH), ISO 21348 (definitions of Solar Irradiance Spectral Categories), also applied in Australian Sunlens Standard AS/NZS 1067:2003 and definition adopted by the World Health Organization (WHO)
UV index by time and season: http://www.who.int/uv/publications/globalindex/en/ - Calbo, J., & González, J. A. (2005). Empirical studies of cloud effects on UV radiation: A review. Reviews of Geophysics, 43(2).
Sliney DH. Physical factors in cataractogenesis: ambient ultraviolet radiation and temperature. Invest Ophthalmol Vis Sci. 1986 May;27(5):781-90.
18. Green AC, Wallingford SC, McBride, P. Childhood exposure to ultraviolet radiation and harmful skin effects: Epidemiological evidence. Prog Biophys Mol Biol. 2011 Dec: 107(3): 349-355
Cook BE Jr, Bartley GB. Treatment options and future prospects for the management of eyelid malignancies: an evidence-based update. Ophthalmology2001 Nov; 108(11):2088-98. - Abraham J, Jabaley M, Hoopes JE. Basal cell carcinoma of the medial canthal region. Am J Surg 1973; Oct; 126(4):492-5.