Why is Sunlight Bad for Your Eyes?
With winter behind us and summer right around the corner, many are looking forward to spending more time outside, but people are also concerned about the potential dangers that sunlight may cause. We’ve all heard the warnings to use sunscreen and wear sunglasses, but it can often be difficult to figure out why these things are necessary or what is at stake. At Georgia Eye Physicians and Surgeons, we are fundamentally concerned with all aspects of eye care. Here is some insight into exactly how excessive exposure to sunlight can affect your eyes.
The sun constantly emits radiation across most of the electromagnetic spectrum, from extremely high frequency x-rays to comparatively low frequency radio waves. The vast majority of this radiation, however, is effectively blocked by the earth’s natural magnetic field and the uppermost layers of atmosphere, leaving only ultraviolet, infrared, and visible light to have a significant impact on the earth’s surface. Of these three, ultraviolet light has the highest frequency and so is potentially the most damaging to living tissue. The ultraviolet light that makes it through the atmosphere is further divided into two levels, UV-A and UV-B, based on their relative frequencies. Each of these forms of UV light has different effect on the human body and the eyes.
The higher energy, more damaging UV-B rays are primarily responsible for sun-tanning and sunburn. However, in high doses, they can cause photokeratitis, a painful inflammation of the cornea somewhat similar to sunburn on the surface of the eye. Photokeratitis can be extremely painful and, in severe cases, can cause temporary blindness, but is usually reversible and does not seem to result in any long-term damage. UV-B radiation also plays a role in causing eyelid conditions and irregular skin growths, or pterygium, which can affect the outermost portions of the eyes. UV-A rays, on the other hand, are closer to visible light rays and have a lower energy level than UV-B radiation, but are potentially even more dangerous. The transparent outer layer of the eye, or cornea, completely blocks UV-B wavelengths, but weaker UV-A light can pass through without you even knowing it, damaging the far more sensitive lens and retina inside the eye itself. Overexposure to UV-A radiation has been linked to the development of certain types of cataracts, and some research suggests UV-A rays may also play a role in development of macular degeneration.
Unfortunately, the damage that sunlight can cause to the eyes is cumulative, which means that even small amounts can slowly accumulate over time, leading to serious visual impairment as you get older. This is why wearing proper eye protection is so important, even in young children. Both plastic and glass lenses can naturally absorb most ultraviolet light while allowing visible light to pass through freely and the lenses of sunglasses are specially treated to provide even greater protection. The American Optometric Association (AOA) recommends wearing sunglasses that block out wavelengths up to 400 nanometers (nm), which effectively reflects 99-100 % of both UV-A and UV-B light. Sunglasses which meet this requirement are usually labeled as “UV 400.”
Taking a few simple precautions while enjoying the outdoors can help preserve your vison and avoid many difficulties in the future. If you have any concerns about your vision, or any questions about how to best maintain the health of your eyes, please contact Georgia Eye Physicians and Surgeons to make an appointment with Dr. William Segal or Dr. Marc Lay to schedule an eye exam. Be sure to follow us on Facebook, Twitter, and Google+ for more information on how to keep your vision clear and healthy.