Two words: Eyelid, sunburn. And if the thought of that kind of torture isn't enough to send sunglasses flying off the shelves, there's also the fact that skipping shades could cause certain types of cataracts, a clouding of the eye's lens, and worsen vision overall. (Sorry, no evidence we need to wear those sunglasses at night… yet.)
Shady Business — The Takeaway
The sun's ultraviolet radiation can cause both short and long-term damage to the eyes Ultraviolet eye radiation: the problem and solutions. Sheedy, J.E., Edlich, R.F. College of Optometry, Ohio State University, Columbus, Ohio, USA. Journal of the Long-Term Effects of Medical Implants, 2004;14(1):67-71.. The immediate effects are pretty obvious: a seriously painful sunburn on the sensitive skin around the eyes. But the long-term effects can be even more problematic. Eye diseases caused by sunlight are known as ophthalmohelioses (say what?!), and include cataracts, damage to the retina, and, eventually, macular degeneration — which all worsen eyesight in their own ways Ultraviolet radiation and the anterior eye. Coroneo, M. Department of Ophthalmology, University of New South Wales, Sydney, Australia. Eye & Contact Lens, 2011 Jul;37(4):214-24. Ultraviolet phototoxicity to the retina. Glickman, R.D. Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX. Eye & Contact Lens, 2011 Jul;37(4):196-205. A review: role of ultraviolet radiation in age-related macular degeneration. Chalam, K.V., Khetpal, V., Rusovici, R., et al. Department of Ophthalmology, University of Florida-College of Medicine, Jacksonville, FL. Eye & Contact Lens, 2011 Jul;37(4):225-32.. Plus, that immediately noticed sunburn repeated over time can result in some seriously scary problems — and sensitive skin around the eyes is especially prone to skin cancer.
But things get complicated when considering sun exposure at different times of the year. One study out of the UK found that Brits get only about ten percent of their lifetime UV exposure during winter months and 60 percent during the summer, and another study found that people in some climates may not actually get enough UV exposure during the winter for beneficial effects (like vitamin D synthesis) Human exposure to solar ultraviolet radiation. Diffey, B.L. Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, UK. Journal of Cosmetic Dermatology, 2002 Oct;1(3):124-30. Is a differentiated advice by season and region necessary? Sliney, D.H., Wengraitis, S. Laser/Optical Radiation Program, USA Center for Health Promotion and Preventive Medicine, Gunpowder, MD. Progress in Biophysics and Molecular Biology, 2006 Sep;92(1):150-60. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. Webb, A.R., Kline, L., Holick, M.F. Vitamin D, Skin, and Bone Research Laboratory, Boston University Medical School, MassachusettsThe Journal of Clinical Endocrinology and Metabolism, 1988 Aug;67(2):373-8.. But researchers in Australia found a substantial proportion of UV exposure occurs in the winter (in part, because people tend to skip protection during cooler months) Seasonal variation in measured solar ultraviolet radiation exposure of adults in subtropical Australia. Neale, R.E., Hamilton, A.R., Janda, M., et al. Cancer and Population Studies, Queensland Institute of Medical Research, Brisbane, Qld, Australia. Photochemistry & Photobiology, 2010 Mar-Apr;86(2):445-8.. It all comes down to location, location, location: Folks living far away from the equator (eh there, we're talkin' aboot you, Canadians) might not need to worry so much about sun protection during the winter, but much of the rest of the world (including almost all of the U.S., South, and Central America) probably should Ultraviolet radiation exposure pattern in winter compared with summer based on time-stamped personal dosimeter readings. Thieden, E., Philipsen, P.A., Wulf, H.C. Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen, Denmark. The British Journal of Dermatology, 2006 Jan;154(1):133-8.. A good indicator of UV exposure, regardless of climate? How much of a shadow someones casts — the longer the shadow, the less UV exposure Is a differentiated advice by season and region necessary? Sliney, D.H., Wengraitis, S. Laser/Optical Radiation Program, USA Center for Health Promotion and Preventive Medicine, Gunpowder, MD. Progress in Biophysics and Molecular Biology, 2006 Sep;92(1):150-60..
But that leaves out one important point: No amount of sun exposure is "good" for eyes. While the skin needs some UV love to properly synthesize vitamin D, the eyes don't need sunlight for any specific reason. Whether it's only 10 percent of our lifetime UV exposure or more than half, being exposed to sunlight in the winter (and fall and spring) can contribute to worsening eyesight. Outdoor sports on a fresh blanket of snow (or ice) can up to double those UV rays, and higher altitudes (we're looking at you, skiers and snowboarders) also up exposure. Check that little sticker on a pair of shades before purchasing to check for both UV-A and UV-B protection between 99 and 100 percent (anything less just won't block it!). And in this case, the bigger the better — larger lenses and wrap-around styles help block out more light than smaller ones Ultraviolet eye radiation: the problem and solutions. Sheedy, J.E., Edlich, R.F. College of Optometry, Ohio State University, Columbus, Ohio, USA. Journal of the Long-Term Effects of Medical Implants, 2004;14(1):67-71..
Throw on some extra-large stunna shades year-round to protect eyes from UV damage. Even in off-peak sun seasons, those rays can do some damage.