People age differently. Some look younger than their years while others look older. A major reason for this is ultraviolet (UV) light exposure. Parts of the body that get little sunlight exposure are always less aged and damaged than the face. People disinclined to go outdoors, or who always use sun block, have more youthful skin than outdoors people who are indifferent to UV radiation.
The same is true of eyesight. Reducing your risk of cataracts and age-related macular degeneration also requires protection from UV. In this case protection means protective sunglasses or prescription sunglasses.
The behavior of UV light is a bit complicated. The reason is that there are three types, each of which behave differently:
- UVA. UVA is the least energetic of the three types. This means it does less damage to human tissue. However, it is the most penetrating of the three types and can penetrate more deeply into human tissue such as the eyes.
- UVB. UVB is more energetic and more damaging to human tissue than UVA, but has less penetrating power. It’s responsible for sunburns. Although it doesn’t penetrate very deep into your skin, it causes greater damage to the tissue that it does reach. Little of it gets past the outer layer of your eyes. But it can sunburn the surface of your eye’s cornea, which causes snow blindness.
- UVC. UVC is the most energetic of the three types of UV light. It’s also the least penetrating. Because it can’t penetrate the earth’s ozone layer, it doesn’t reach the ground.
The Problem with UVA
The public’s poor understanding of the different types of UV leads to the wrong conclusions about its hazards. The main misconception is that situations where sunburn is less likely to occur, such as on cloudy days, must mean that you are safe from the damaging effects of UV. However, situations where you don’t get sunburned only mean you’re safe from the effects of UVB. You aren’t safe from UVA. As mentioned previously, UVA is the most penetrating of the three types of UV and therefore can damage your eyes even on cloudy days.
Because UVA is the weakest of the three, it also takes longer for its damaging effects to become noticeable. For example, UVA exposure has been linked to eye cataract and macular degeneration problems that occur later in life. UVA’s relative weakness is the reason these problems take so long to manifest.
Cataracts are a clouding of the eye’s lens. Little to no UVB can penetrate into the lens of the eye. Only UVA can do this. Much of the UVA radiation is absorbed into the lens where it slowly does its damage. Some UVA makes it through the lens and penetrates the macula at the back of the eye near the center of the retina. Research indicates that UVA exposure is linked to macular degeneration.
The Pervasiveness of UVA
The penetrating power of UVA means that clouds offer no protection. It also means there’s much more of it than UVB. UVA accounts for 80 to 95 percent of the UV radiation that reaches the ground. UVA penetrates the atmosphere more easily than UVB.
Even the side windows of many cars don’t block UVA. The windshields of cars have a polymer middle layer that prevents shattering. This polymer blocks UVA and UVB. However, the side windows only block UVB. If you regularly commute to work in your car, your exposure to UVA is substantial. This photo of a truck driver shows what 28 years of UVA exposure can do. The left side of his face (which was exposed to the left side window) is aged by UVA.
The eyes are similarly exposed. Adequate eye protection requires sunglasses with polycarbonate or Trivex lenses, or with a UVA/UVB blocking coating on the lenses. Wraparound designs work best at blocking UV coming in from the side. In addition, an anti-reflective lens coating prevents UV radiation from reflecting into your eyes from the inside lens surface.
When you’re outdoors or in a car, you should always wear sunglasses with 100% UVA/UVB protection. Nike offers sunglasses with complete UV protection and has many frame styles and lens options. The same is true for Nike prescription sunglasses. For more details, contact us.