Sunday, June 5, 2016

Sunglasses don't just look cool, they protect your eyes and lids

Skin is sensitive to the sun's ultra-violet radiation. Ask Ellie!
Photo: George Powell
Summer's already here unofficially in North America. Time for us all to hit the beach remember to wear sunblock, a hat, and sunglasses.

Sunlight helps us maintain sufficient vitamin D in our systems, historically warding off tuberculosis and ricketts and possibly lowering the risk of some cancers (lung, colon, and breast cancers).

However, exposing our skin to too much ultraviolet (UV) light contributes to a host of health problems, sunburn being just the most immediate and obvious.


The radiation causes our skin to age more quickly (wrinkles, loss of elasticity) and produce brown spots (e.g. freckles, "age" spots) from melanin to help protect it from further damage.

Skin cancer is the biggest problem. UVA radiation (over 95% of the UV radiation that reaches Earth’s surface) penetrates the skin, where it can contribute to skin cancer by generating DNA-damaging molecules hydroxyl and oxygen radicals.

Our eyes and eyelids are equally vulnerable: skin cancer on the eyelids can be difficult to detect, so be sure to check for any changes to eyelashes or eyelids. UV light can cause not only eye cancers but also lead to:
  • Corneal burns and inflammation (photokeratitis)
  • Cataracts (clouding of the lens of the eye)
  • Solar Retinopathy (damage to the retina)
  • Macular degeneration (deterioration of the central part of the retina, the macula)
  • Benign growths on the eye.
Not good.

Happily, sunglasses can function like sunblock for your eyes, but to be effective, they need to offer sufficient protection from the various UV rays.


So what offers good protection?


The Mayo Clinic in the U.S. recommends that to protect your eyes, look for sunglasses that:
  • Block 99 to 100 percent of both UVA and UVB rays
  • Screen out 75 to 90 percent of visible light
  • Have lenses that are perfectly matched in color and free of distortions and imperfections
  • Have lenses that are gray for proper color recognition
  • Wrap around your eyes or fit closely, to reduce glare from the sides as well.

The American Academy of Opthamology guidelines support these standards, saying sunglasses should:

Block 99% of ultraviolet (UV) rays
  • This includes UVA and UVB radiation, which is considered more dangerous to the eyes and skin than UVA radiation.
  • Look for sunglasses that block 99-100% of UVA and UVB light. sometimes labeled as "UV absorption up to 400nm." (This is the same as 100% UV absorption.)
  • Both plastic and glass lenses absorb some UV light, and lenses show have coatings or materials that improve UV absorption.

Photo: AllAboutVision
Have Polarized lenses
  • These cut reflected glare — the sunlight that bounces off smooth surfaces like pavement, car windows, or water, making them particularly useful for driving, fishing or boating.
  • While polarization is not related to UV light absorption, many polarized lenses now have a UV-blocking substance.
  • You should still check the label on the sunglasses to make sure they provide maximum UV protection.

Wrap around your eyes or fit closely to your face
  • Studies have shown that enough UV rays enter around ordinary eyeglass frames to reduce the benefits of protective lenses.
  • Wraparound sunglasses or those with wide arms adjacent to your temples are shaped to keep light from shining around the frames and into your eyes.
  • Large-framed wraparound sunglasses can protect your eyes from all angles.

Wrap-around glasses with a broad side band.
Flames are extra. Photo: MaximumEyewear
Glacier glasses protect eyes from the sides,
as well as the front. Photo: AmazonUK

Meeting official safety standards
While no universal standard for sunglass protection capacity yet exists, three regional standards have been created:
  • The Australian Standard AS/NZS 1067:2003 rates sunglasses from 0 to 4 based on the amount of absorbed light. The "0" rating provides some initial protection from UV radiation and sunglare, and "4" indicates a high level of protection (don't wear when driving).
  • The European standard EN 1836:2005 has four protection ratings: 0 for insufficient UV protection, 2 for sufficient UHV protection, 6 for good UHV protection and 7 for full UHVV protection. The standard rates only radiation up to 380 nm, not up to 400 nm ("UV400"), as required in other countries (incl. the United States) and recommended by experts.
  • The U.S. standard is ANSI Z80.3-2001, with 3 protection categories, and the lens should allow no more than 1% of UVB (280 to 315 nm) transmittance and no more than 0.3 times the visual light transmittance for UVA (315 to 380 nm). 

Additional safety standards require lenses to resist certain impacts, such as a metal object flung at the lenses.


What features do not necessarily protect your eyes from UV radiation?


Mirrored lenses look cool and make your owner
wonder what you are (not) thinking.
Photo: BoredomKicker, Pinterest
Lens darkness
  • Most standard colors (gray, brown, green, or yellow) will work for normal wear, but you would want a darker lens if you will be wearing the glasses in very bright conditions (e.g. snow, waterskiing).
  • The color and darkness do not tell you anything about the lenses' ability to block UV light. You can even put a clear UV blocking coating on your regular glasses, though you'd still probably squint.

Mirror coated lenses
  • Mirror finishes are thin layers of various metallic coatings on an ordinary lens. 
  • They look cool and allow you to close your eyes while talking to people.
  • They reduce the amount of visible light entering your eyes, but they may not fully protect you against UV radiation.

Photochromic lenses
  • These lenses automatically darken in bright light and lighten in low light, which can be super convenient, especially for prescription eyeglasses.
  • Like overall lens color, this process (which takes 30 seconds to 5 minutes) is also independent of the glasses' ability to block UV light, so you should ensure that the label states that they do.

Gradient lenses
Best times to be out on the beach are
early and late in the day.
Bonus: gorgeous skies!
  • Single gradient lenses are shaded at the top of the lens and lighter on the bottom, which can cut glare from the sky but allow you to see clearly below. 
  • This configuration makes them useful for driving (so you can still see your dashboard) but not for the beach or snow, where light comes in from below.
  • Double-gradient lenses are dark on top and bottom and lighter in the middle can help with light reflected up off the snow or water but make it harder to drive!

Blocks 90% of infrared rays
  • Infrared wavelengths are invisible and produce heat. 
  • Sunlight has low levels of infrared rays, and the eye tolerates infrared well.
  • Also, research has not shown a close connection between eye disease and infrared rays.

If all this information isn't enough for one day, you can try this quiz about sunglasses - then learn more here and here, or on the other links in this post. I learned a lot researching this post!

1 comment:

  1. I find this blog with very educative and helpful content on sunglasses, i only they look cool and didnt know they protect our eyes from light rays.

    ReplyDelete