Ultraviolet - Uv rays Protection
The sun supports life on our planet, but its life-giving rays also pose dangers. The sun’s primary danger is in the form of ultraviolet (UV) radiation. Artificial sources, like welding machines, tanning beds and lasers, can also produce UV radiation.
Most people are aware of how harmful UV radiation is to the skin. However, many may not realize that UV radiation can harm the eyes, and other components of solar radiation can also affect vision.
There are three types of UV radiation. UV-C is absorbed by the ozone layer and does not present any threat. However, UV-A and UV-B radiation can have long- and short-term negative effects on the eyes and vision.
If your eyes are exposed to excessive amounts of UV radiation over a short period of time, you will likely experience photokeratitis. Like a “sunburn of the eye,” photokeratitis can be painful. Its symptoms include red eyes, a foreign body sensation or gritty feeling in the eyes, extreme sensitivity to light and excessive tearing. Fortunately, these symptoms are usually temporary and rarely cause permanent damage to the eyes.
What is Uv?
Sunlight is the main source of UV rays. Tanning lamps and beds are also sources of UV rays. People who get a lot of UV exposure from these sources are at greater risk for skin cancer.
Even though UV rays make up only a very small portion of the sun’s rays, they are the main cause of the sun’s damaging effects on the eye and skin. UV rays damage the DNA of cells. Skin & Eye cancers start when this damage affects the DNA of genes that control skin cell growth.
There are 3 main types of UV rays:
- UVA rays age skin cells and can damage their DNA. These rays are linked to long-term skin damage such as wrinkles, but they are also thought to play a role in some skin cancers. Most tanning beds give off large amounts of UVA, which has been found to increase skin cancer risk.
- UVB rays have slightly more energy than UVA rays. They can damage cells’ DNA directly, and are the main rays that cause sunburns. They are also thought to cause most skin cancers.
- UVC rays have more energy than the other types of UV rays, but they don’t get through our atmosphere and are not in sunlight. They are not normally a cause of skin cancer.
Both UVA and UVB rays can damage skin and cause skin cancer. UVB rays are a more potent cause of at least some skin cancers, but based on what’s known today, there are no safe UV rays.
The strength of the UV rays reaching the ground depends on a number of factors, such as:
- Time of day: UV rays are strongest between 10 am and 4 pm.
- Season of the year: UV rays are stronger during spring and summer months. This is less of a factor near the equator.
- Distance from the equator (latitude): UV exposure goes down as you get further from the equator.
- Altitude: More UV rays reach the ground at higher elevations.
- Cloud cover: The effect of clouds can vary. Sometimes cloud cover blocks some UV from the sun and lowers UV exposure, while some types of clouds can reflect UV and can increase UV exposure. What is important to know is that UV rays can get through, even on a cloudy day.
- Reflection off surfaces: UV rays can bounce off surfaces like water, sand, snow, pavement, or grass, leading to an increase in UV exposure.
The amount of UV exposure a person gets depends on the strength of the rays, the length of time the skin is exposed, and whether the skin is protected with clothing or sunscreen.
People who live in areas with year-round, bright sunlight have a higher risk of skin cancer. Spending a lot of time outdoors for work or recreation without protective clothing and sunscreen increases your risk.
The pattern of exposure may also be important. For example, frequent sunburns in childhood may increase the risk for some types of skin cancer many years or even decades later.
Skin cancers are one result of getting too much sun, but there are other effects as well. Sunburn and tanning are the short-term results of too much exposure to UV rays, and are signs of skin damage. Long-term exposure can cause early skin aging, wrinkles, loss of skin elasticity, dark patches (lentigos, sometimes called age spots or liver spots), and pre-cancerous skin changes (such as dry, scaly, rough patches called actinic keratoses).
The sun’s UV rays increase a person’s risk of cataracts and certain other eye problems, too. They can also suppress the skin’s immune system. Darker-skinned people are generally less likely to get skin cancer than light-skinned people, but they can still get cataracts and immune suppression.
The UV Index
As noted above, the amount of UV light reaching the ground in any given place depends on a number of factors, including the time of day, time of year, elevation, and cloud cover. To help people better understand the strength of UV light in their area on a given day, the National Weather Service and the Environmental Protection Agency (EPA) have developed the UV Index. It gives people an idea of how strong the UV light is in their area, on a scale from 1 to 11+. A higher number means greater risk of exposure to UV rays and a higher chance of sunburn and skin damage that could ultimately lead to skin cancer.
The UV Index is given daily for regions throughout the country. Many television, online, and smartphone weather forecasts include the projected UV Index. Further information about the UV Index, as well as your local UV Index forecast, can be found on the EPA’s website at www.epa.gov/sunsafety/uv-index-1. Smartphone apps are available from the EPA at www.epa.gov/enviro/uv-index-mobile-app. As with any forecast, local changes in cloud cover and other factors could change the actual UV levels experienced.
Protecting Your Eyes from Shorter-Wavelength Visible Light
Chronic exposure to shorter-wavelength visible light (blue and violet light) may also be harmful to the retina. Many digital devices emit this shorter-wavelength visible light.
Blue light is part of the visible light spectrum. The sun emits blue light, as do artificial light sources, such as LEDs, computers and smartphones. Some types of blue light can be beneficial, helping us regulate our bodies’ internal biological clocks.
However, blue-violet light can be harmful to the eyes, specifically the retina. It is a risk factor for the onset of age-related macular degeneration, a deterioration of the part of the retina responsible for sharp, central vision.
A recent study found that Americans spend almost 2 ½ hours on their tablets and smartphones every day. In addition, most offices and stores use fluorescent light bulbs, and LED lights are becoming increasingly popular.
Lenses that absorb harmful blue light but allow beneficial blue light through your lenses are entering the marketplace. You could also apply a special clear coating to traditional lenses to enhance their ability to block these harmful rays while you use computers and smartphones.
UV Radiation Checklist
If you can answer “yes” to one or more of the following questions, you could be at higher risk for harm to the eyes from UV radiation:
See your doctor of optometry every year for a comprehensive eye examination. It is a good way to monitor your eye health, maintain good vision and keep track of your solar radiation protection needs, as well as advances in eye protection.
Wear sunglasses that block UV rays
The longer the eyes are exposed to solar radiation, the greater the risk of developing cataracts or macular degeneration later in life. It is not clear how much exposure to solar radiation will cause damage. Therefore, whenever you spend time outdoors, wear quality sunglasses that offer UV protection and a hat or cap with a wide brim. Also, certain contact lenses can provide additional UV protection.
UV-blocking sunglasses are important for protecting the delicate skin around the eyes, as well as the eyes themselves. Research has shown that long hours in the sun without protecting your eyes increase your chances of developing certain eye diseases.
To provide adequate protection for your eyes, sunglasses should:
- block out 99 to 100 percent of both UV-A and UV-B radiation, Before you buy, check the label to make sure they do. Labels that say “UV absorption up to 400 nm” or “Meets ANSI UV Requirements” mean the glasses block at least 99% of UV rays. Those labeled “cosmetic” block about 70% of UV rays. If there is no label, don’t assume the sunglasses provide any UV protection.
- screen out 75 to 90 percent of visible light;
- have lenses that are perfectly matched in color and free of distortion and imperfection; and
- have lenses that are gray for proper color recognition.
Darker glasses are not necessarily better because UV protection comes from an invisible chemical in or applied to the lenses, not from the color or darkness of the lenses. Look for an ANSI label.
Large-framed and wraparound sunglasses are more likely to protect your eyes from light coming in from different angles. Children need smaller versions of real, protective adult sunglasses – not toy sunglasses.
Ideally, all types of eyewear, including prescription glasses and contact lenses, should protect against UV rays. Some contact lenses are now made to block most UV rays. But because they don’t cover the whole eye and surrounding areas, they are not sufficient eye protection when used alone.
If you participate in potentially eye-hazardous outdoor work or sports, your sunglass lenses should be made from polycarbonate or Trivex® material. These lenses provide the most impact resistance.
If you spend a lot of time outdoors in bright sunlight, consider wearing wraparound frames for additional protection from the harmful solar radiation.
Don’t forget protection for children and teenagers. They typically spend more time in the sun than adults.
- American Optometric Association
- American Cancer Society