How To Choose Sunglasses, Do You Need Them?

How to choose sunglasses
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When choosing a pair of sunglasses, some people select strictly based on style, others on the amount of eye protection, and some on a combination of the two. Several experts and recent research offer some helpful information on how to choose sunglasses and even question whether you need them.

What kinds of light can damage your eyes?

If you are in the market for a pair of sunglasses that will help protect your eyes against harmful ultraviolet (UV) rays—both UVA and UVB-- one important thing to remember is that darker lenses are not better than lighter ones. Darker lenses can harm your eyes because your pupils don’t constrict, which then allows too much sunlight to enter your eyes, according to Edward Kondrot, MD, an ophthalmologist who commented in a MedPage Today article.

In fact, a new study published in the journal International Ophthalmology explains there is “strong evidence that ultraviolet radiation (UVR) exposure is associated with the formation of eyelid malignancies [basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)], photokeratitis (burned cornea by UVB), climatic droplet keratopathy (CDK; degenerative condition of the cornea), pterygium (a noncancerous growth on the eye), and cortical cataract.”

In the same report, the authors stated there was “insufficient evidence” to state whether age-related macular degeneration is associated with exposure to UV rays. However, they did note that this eye disease is likely related to blue light and other visible radiation.

How do you identify good sunglasses?
Experts generally agree you should shop for sunglasses with lenses that block out UVA and UVB rays, which can damage your DNA. Ultraviolet rays are in the range of 100 nanometers (nm) to 400 nm. Specifically:

  • UVA range from 320 nm to 400 nm; the majority of UV rays that reach the earth are UVA, and they are longer than UVB rays
  • UVB range from 290 nm to 320 nm; they are shorter than UVA rays and mostly absorbed by the ozone layer
  • UVC range from 100 nm to 290 nm and are completely absorbed by the ozone layer and atmosphere

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The eyes can be affected by both UVA and UVB rays, with the shorter waves (UVB) affecting the cornea and the longer waves having the ability to reach the retina and lens. Therefore, shop for sunglasses that block UV rays, and don’t worry so much about how dark the lenses are.

For example, sunglasses advertised as absorbing up to 400 nm or those that say they absorb 99% of UV rays means they have the ability to block up to all of the incoming UV rays. If you like the look of polarized lenses, you should know that while they can reduce glare, they don’t help with fighting UV rays at all.

Do you really need sunglasses?
Every issue has two sides, and the question about sunglasses is no exception. According to Kondrot, not everyone needs sunglasses. In fact, he recommends their use only for his patients who have certain eye diseases, who have undergone cataract surgery, or who engage in prolonged sunlight exposure.

In MedPage Today, Kondrot explained that the human eye has built-in ways to protect itself against harmful rays, such as squinting and looking away from the sun. He noted that such natural responses have “helped people survive for tens of thousands of years.”

Most experts, however, continue to believe the use of sunglasses is a good idea for eye protection. So when it’s time to choose sunglasses, don’t go just for the most stylish: be sure you protect your eyes against harmful UV rays as well.

SOURCES:
MedPage Today
Yam JC, Kwok AK. Ultraviolet light and ocular diseases. International Ophthalmology 2013 May 31. Epub ahead of print

Image: Pixabay

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