How Sunglasses Work

Posted by: Georgia Eye Physicians and Surgeons in Latest News

The eye-care specialists at Georgia Eye Physicians and Surgeons can treat a variety of conditions that impact vision, but we understand that most people would rather never suffer from visual impairment at all.  Fortunately, there are many preventative measures you can take to help keep your eyes healthy and sharp.  One of the most common is the regular use of a high quality pair of sunglasses.

The visible light our eyes can see actually makes up only a portion of the electromagnetic spectrum, which also includes radio waves, gamma rays, and even x-rays.  All of this radiated energy vibrates as it travels, with more powerful waves vibrating at faster rates, or higher frequencies.  Wavelengths at a higher frequency than visible light, like gamma rays, x-rays, and ultraviolet rays, are powerful enough to damage or even destroy living tissue.  While the most damaging forms of radiation produced by the sun are screened out by the earth’s magnetic field and upper atmosphere, ultraviolet radiation in the form of UV-A and UV-B rays constantly bombards us, burning unprotected skin and potentially leading to numerous other health concerns.  The eyes are particularly prone to the adverse effects of ultraviolet radiation, which can cause photokeratitis, snow blindness, cataracts, pterygium, and various forms of eye cancer.

This is why wearing proper eye protection is so important.  Both plastic and glass lenses naturally absorb a certain amount of ultraviolet light while allowing visible light to pass through freely, but ultraviolet absorption can be improved further by adding chemicals to the lens material during manufacturing or by applying special lens coatings.  These alterations make the glass opaque to the shorter, more energetic wavelengths while allowing the longer ones, like visible light, to pass through.  The American Optometric Association (AOA) recommends wearing sunglasses that block out wavelengths up to 400 nanometers (nm), which effectively reflects 99-100 % of UV-A and UV-B light.  Sunglasses which meet this requirement are often labeled as “UV 400.”

However, high quality sunglasses can actually do more than just block out damaging ultraviolet radiation.  They can also help reduce the glare produced by reflective surfaces like water or pavement.  While this does not offer any more protection from the sun, it can make activities like driving or being on the water safer or more enjoyable.  When the intensity of visible light exceeds the levels that can be comfortably absorbed by the retina, we perceive these brighter areas as vague flashes of white, or glare.  Ordinarily, the glare that causes you to wear sunglasses comes from horizontal surfaces, such as water or a highway.  Polarized lenses in sunglasses are fixed at an angle that only allows vertically polarized light to enter, screening out much of the light reflected off of horizontal surfaces and eliminating the glare that can obscure vision.

Finally, premium sunglasses can also incorporate a number of other secondary features, like scratch resistant or anti-reflective coatings to improve convenience and functionality.  Tinted lenses can even eliminate specific frequencies of light, improving visual contrast and sharpness under specific conditions.  Consult with one of the specialists at our optical center to determine what features would best suit your specific needs.  If you have any additional questions about any of the optical services we offer, or would like to schedule an eye exam, please contact Georgia Eye Physicians and Surgeons today. Be sure to follow us on Facebook, Twitter, and Google+ for more to keep your vision healthy.