The ability to feel pain when our tissue is damaged causes us to avoid harmful situations. This is why it’s difficult to deliberately place one’s hand into a blast furnace. Our skin would sense the infrared (heat) radiation long before any damage is done. However, we can’t directly sense ultraviolet (UV) radiation, and because of this, we can easily overexpose ourselves to its harmful effects. That’s why you aren’t aware of your skin burning from UV radiation until after the damage is done when it’s sunburned.
The same is true of UV damage to the eyes. Unlike a sunburn, from which you can recover, UV eye damage can cause blindness from macular degeneration, and cataracts, which are a clouding of the eye lens. UV light can cause a growth in the white part of the eye called a pterygium. Recovery from these kinds of injuries when possible, often requires surgery.
Most people are aware that UV radiation is harmful to the eyes. Because UV doesn’t induce pain like heat radiation, it’s easy to simply shrug it off. Another problem is that UV eye damage can take years and even decades of exposure before its harmful effects to the eyes become apparent. This delayed reaction can convince some people that UV eye damage won’t happen to them.
Yet another problem is that UV insensitivity can cause you to expose yourself in situations that you think should be safe, such as when clouds are blocking the sun.
Factors That Influence Ultraviolet Exposure
Because you can’t sense UV radiation, you must be aware of situations that place you at risk. These include:
Sunshine, including its UV component, is most intense above the equator. In these regions of the world, UV light comes straight down through the atmosphere from space. This means it takes the shortest, most direct path through the atmosphere. In northerly and southerly latitudes, sunlight angles through more atmosphere, which absorbs more UV light.
You can get an idea of the UV exposure for your locality by looking up the UV index for your region. From the UV index you can look up exposure times that cause sunburn. If you live in an area with a high UV index, Nike Prescription Glasses with UV Protection is a good idea.
Time of Day and the Season
The higher the sun is in the sky, the less atmosphere it travels through before reaching you. Therefore, exposure is greatest in the summer during the solar noon hours (a period of about 4 hours). It’s least intense during sunrise and sunset in the winter. However, don’t get too relaxed in the winter because sun reflection from snow cover can more than make up for this, especially during the noon hours.
The greater your altitude, the less atmospheric protection above your head. Keep this fact in mind when vacationing in or moving to a mountainous area. For every 1000 meters (3,281 feet), your UV exposure increases by about 11%. For example, if you live in Boston and decide to hike to the top of Mount Washington (6,289 feet altitude) in New Hampshire, your UV exposure will increase by about 21%.
Cloud cover will reduce UV radiation. However, this depends on the thickness of the cover. If you’re underneath very dark clouds, lightning strike is your primary concern rather than UV exposure (which is minimal). Thin wispy clouds provide negligible protection. An intermediate cloud thickness simply delays the harmful effects of UV exposure. If you are doing a day long bike ride on a cloudy day, protect your eyes with Nike prescription sunglasses.
Wearing a hat with a brim does little good when standing on a snow field, a beach, a boat in the water, or on concrete. All of these surfaces reflect UV light to your eyes from below. Metal surfaces and even sea-foam reflect UV light.
Believe it or not, if you can see the blue sky when standing in a shaded spot, UV radiation is still reaching your eyes. The atmosphere scatters UV light in all directions. When you look at a section of the sky, scattered UV light is entering your eyes. Blue light also does the same thing, which is why the sky is blue.
Do your prescription glasses provide 100% UVA and UVB protection? If not, get a pair of Nike prescription sunglasses or Nike prescription glasses with UV protection. Contact us for more details.