Friday, April 4, 2014

Sun Protection 101

After a bitter and seemingly endless winter, spring has finally sprung in New England!  In honor of sunny days to come, I've decided to put together some things to take into consideration when selecting sunglasses.  And, more expensive does not necessarily mean better!  Read on for some tips to make your time in the sun safer and more comfortable (and look like a rock star, while you're at it):

1.  UV Protection: 

There are three types of UV light -- UVA, UVB, and UVC.  UVA radiation, albeit less damaging than UVB, is the most prevalent and can contribute to early aging (wrinkles, cataract development).  UVB light is the most intense form of UV light and is responsible for sunburns.  Both UVA and UVB light likely contribute to cataract development, macular degeneration, and cancers of the sensitive skin along the eyelid.  UVC radiation is blocked by the atmosphere and does not reach earth.

It is crucial to note that UV light can easily pass through clouds; so, don't forget sunglasses on an overcast day!  Rays are strongest between 10am and 2pm.  Additionally, things like sunlamps, tanning beds, and photosensitizing drugs increase your risks.  Those that live at high altitudes or near the equator should exercise additional caution.

Look for sunglasses that offer protection from 99 to 100 percent of both UVA and UVB radiation. This includes those labeled as "UV 400," which blocks all light rays with wavelengths up to 400 nanometers (which covers UVA and UVB light).  Also, wraparound sunglasses are beneficial because they can limit UV rays entering from the sides of the frame.


2.  Impact Resistance:

By FDA standards, all sunglasses must meet certain impact standards.  However, no lens is truly unbreakable.  Plastic lenses are less likely to shatter when compared with glass (virtually no glasses are actually made of glass, as ironic as it sounds).  Lenses made of material like polycarbonate or Trivex are used in many sports sunglasses.  These materials are incredibly tough (ie they will not shatter), but may scratch easily.  If you buy polycarbonate lenses in particular, look for those with scratch-resistant coatings.

3.  Polarization:

Polarized lenses cut reflected glare, such as that reflected off water or pavement.  They are especially helpful for water activities (fishing, boating), and skiing.  They are also particularly useful for driving on a sunny day.  Keep in mind, polarization has nothing to do with UV protection; though, some polarized lenses are now combined with a UV blocking substance.  If you opt for polarization, also make sure the lenses include UVA and UVB protection. 

One other thing to keep in mind regarding polarized lenses is that they may reduce the visibility of images produced by LCDs or LEDs found on the digital screens of ATMs, self-service gas pumps, and the dashboards of some cars.  With polarized lenses, you will likely also have trouble seeing your cell phone or GPS device.  In particular, pilots generally should not get polarized lenses as it can render LCD displays on instrument panels nearly invisible.


4. Lens color/darkness

This is mostly a matter of personal preference.  While you may be more comfortable in bright sunlight with a darker tint, keep in mind the lens color says nothing about UV protection.  In fact a dark tint without UV protection can cause more harm than a lighter shade without UV protection, as the pupils of your eye will dilate more with the darker tint allowing more UV light to pass through and damage your lens and retina!  So, again, regardless of the color of the lenses, make sure they also include 99-100% of UVA and UVB protection.

Athletes like skiers and target shooters may prefer yellow tints because they work well in low light, can reduce haze and improve contrast for a sharper image.

4.  Mirror-coated lenses

Mirror-coated lenses (also called "flash-coated") are highly reflectived surfaces on the front of lenses so they limit the amount of light entering the eye.  They are very useful for outdoor activities in bright sunlight.  Mirror coatings are available in nearly any color, and the choice as to which color is purely cosmetic; they all work the same way.  The color of the mirror coating in no way affects your color vision (though the lens color/tint itself can have some effect on color perception).

5.  Photochromic lenses:

Often referred to by a popular name brand, "Transitions," photochromic lenses are the type of lenses that darken in sunlight.  The amount they darken is based on the amount of UV light to which they are exposed.  While there are some newer types of photochromic lenses that will darken inside a vehicle, most do not achieve an adequate amount of darkening (since the windshield blocks UV light), making them a  less than ideal choice for driving.  They are great for people (especially kids) who wear prescription glasses and prefer not to have a second set of prescription sunglasses.

6.  Gradient and double gradient lenses:

Gradient lenses are darker at the top of the lens than the bottom.  They are popular for driving, as the darker portion allows for greater comfort when looking at the road, but the lighter shade on the bottom still allows the dashboard to be seen easilty.  Double gradient lenses are tinted from the bottom up, in addition from the top down.  They can help shield your eyes from both overhead light and light reflecting from water or pavement.


7.  Blue-blocking 
 
While it is still controversial if blue light (from electronics) is damaging to your eyes, lenses are now available that block this wavelength.  The jury is still out, but this may be a good option for those who currently have, or have a strong family history of, macular degeneration or cataracts.



While everyone can benefit from sun protection, keep in mind that certain people have a greater risk for eye conditions stemming from UV light exposure.  Certain medications -- Psoralens (used in treating psoriasis), tetracycline, doxycycline, allopurinol, and phenothiazine  -- can make your skin and eyes more sensitive to light, raising the risk for eye disease.  Contact lens wearers should investigate whether their contacts offer UV protection (some do!); similarly, those that have undergone cataract surgery may want to ask their surgeon whether their artificial lens includes UV protection.  If they do not, sunglasses are even more crucial. 

Additionally, sunglasses cannot protect your eyes from certain intense light sources such as arc welding, tanning lights, snowfields, or sun gazing, especially during a solar eclipse.  Looking at any of these light sources without adequate protection can cause painful changes to the cornea as well as loss of vision if the retina is affected.


I hope this guide was helpful!  Happy spring to all; enjoy those rays of sunlight safely!








some information sourced from:
http://www.allaboutvision.com/faq/sunglasses.htm
http://www.aao.org/eyecare/tmp/sunglasses.cfm







1 comment: