What is Ultraviolet Radiation?
Ultraviolet (UV) Radiation is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than that of x-rays. Specifically, it’s radiation with wavelengths in the spectrum between 400nm and 100nm. The three types of UV radiation we’re concerned with regarding eye protection are UVA, UVB, and UVC, in order from longest to shortest wavelengths, respectively. While UV radiation is often referred to as UV light, that is technically incorrect because you cannot see UV rays with the naked eye.
How is UV Radiation dangerous to our eyes?
Ultraviolet radiation is dangerous to the human eye for several reasons. If too much UV radiation is absorbed by the eye, structures such as the cornea, lens, and the retina can be badly damaged. Pterygia and pingueculae, which are unsightly formations on the eye’s surface, are cause by overexposure to UVB rays and can cause corneal problems and obstruct vision. Photokeratitis, also known as snow blindness or arc eye (mountaineers and welders are particularly at risk) is akin to a sunburn of the cornea/conjunctiva and is caused by overexposure to UV rays. Other serious effects of UV overexposure include macular degeneration and cataract formation, both of which can lead to blindness.
What factors increase risk of overexposure to UV Radiation?
Several factors including geographic location, altitude, time of day, environment, and medication can increase the risk of overexposure to ultraviolet rays.
Geographic Location – UV levels increase closer to Earth’s equator and decrease further away from it
Altitude – UV levels increase at high altitude
Time of Day – UV levels are highest at midday
Environment – open spaces, particularly ones that are snow-covered or reflective surfaced, increase UV levels – sometime by as much as 100%. UV levels in cities and urban settings are typically lower
Medication – certain medications such as tetracycline, sulfa drugs, birth control pills, diuretics, and tranquilizers can increase the body’s sensitivity to UV rays
Note: cloud cover does NOT significantly reduce UV levels. Current UV Index levels for the United States can be found here.
How can we protect our eyes from UV Radiation?
Sunglasses can provide excellent eye protection from harmful UV rays! Look for sunglasses that block 100% of UV rays. Frames with large lenses or wraparound frames provide the best coverage. Not all sunglasses block 100% of UV rays, so be sure to examine the documentation of your sunglasses to know how well you’re protected. Also know that the amount of UV protection sunglasses provide is unrelated to the color and darkness of the lenses.
It is not clear exactly how much exposure to solar radiation will cause eye damage, and also differs from one person to the next, but the American Optometric Association recommends wearing quality sunglasses that offer UV protection in addition to wearing a hat or cap with a wide brim whenever you spend time outdoors. So if you don’t already, bring a pair of quality 100% UV protective sunglasses to the beach, to the park, or anywhere you spend time outdoors.