Sunglasses Article
Introduction:
There are three types of UV (ultra-violet) rays. UVC is blocked by the ozone layer, and therefore will not be discussed in this article.
It is highly recommended to select eyewear that will block both UVA and UVB. These glasses are labeled UV 400.
Resist the temptation to purchase cheap sunglasses.
They typically only block around 65% of UV rays. Moreover, they are made using less-than-optimal quality lenses which can include distortion. This, in turn, can lead to eye strain and possibly headaches.
It is important to know that ultraviolet can go right through clouds. Therefore, it is advised to wear UV protection even if it is not a clear sunny day.
Kids and teenagers should also wear sunglasses whenever not in school (Schools tend to frown upon kids wearing sunglasses, even if it is only outside during recess). Their eyes are still developing, making them even more susceptible to UV damage.
UV rays coming from the temporal sides can be very damaging as well.
These rays are condensed by the cornea onto the nasal conjunctiva, facilitating pinguecula (yellow bump on the white of the eye), which can lead to pterygium formation over time. A pterygium is defined as the conjunctiva growing over the cornea.
UV rays hitting the eye straight on are even more damaging, causing cataracts (lens turning opaque, similar to looking through a very dirty windshield) and macular degeneration (loss of central vision).
Protect your eyes:
1. Polycarbonate lenses. This type of lens has a built-in UV-blocker, which prevents 99% of UV rays from going through. Since it is a clear lens, light will still be very bright. Also, this lens does not block UV rays coming from the sides.
2. UV-blocking lenses. Lenses, made plastic are coated with a UV blocker. They retain a very slight yellow hue after the coating process. Furthermore, they not block UV rays coming from the sides.
3. Clip-ons. They have to be mounted on regular glasses every time UV may be present. Clip-ons are therefore only useful to people already wearing glasses. They will block both UV and light. However, they do not block UV rays coming from the sides.
4. Fit-overs. This option is also only for people already wearing glasses. Other than the fact that they do not need to be mounted on glasses, they are very similar to clip-ons. The main difference is that they block UV rays coming from the sides as well as from directly in front.
5. Transitions. These lenses go from clear to dark in the presence of UV rays. It is another option useful only to those who need prescription glasses. The main drawbacks are that they do not block UV rays coming from the sides, and that the lenses do not get very dark inside cars. This is due to the fact that the windshield blocks most of the UV rays needed to make the lenses change color.
6. Sunglasses (with prescription or not). This is the best option. Especially the wrap-around designs that block UV rays from every direction.
Notes:
Polarized eyewear does not block more UV rays, but eliminates glare, for a much more comfortable experience. Polarized lenses are available for options 3,4 and 6.
Warning:
UV rays are not the only cause of cataracts, macular degeneration, pinguecula and pterygium.
For example, macular degeneration can also be attributed to tobacco. A pterygium can result from wind or dust.
Therefore, wearing UV-blocking eyewear may not be sufficient in preventing these eye diseases, but it will definitely slow them down.
