Ultraviolet is an invisible but highly energetic type of light. It’s energetic in the sense that it can change molecules. This includes molecules that make up the tissues of the eyes. Two types of ultra violet light reach the earth’s surface: UVA and UVB. When UVB causes damage, you’ll know about it within a few hours. It’s what causes sunburn and snow blindness. Fortunately, its penetrating power is limited in that it won’t pass through glass and doesn’t penetrate very deeply into the skin or the eyes.
On the other hand, UVA has greater penetrating power but is less energetic than UVB. This means it takes longer for UVA to do extensive damage. With enough years of exposure, UVA may cause serious eye problems that can threaten blindness. UVA penetrates ordinary glass as well as cloud cover. When you hear or read advice about always wearing UV blocking sunglasses while outdoors, protection against UVA is one of the main concerns.
The problem with this advice is that it’s difficult for many people to consistently wear sunglasses 100% of the time when outdoors. Always carrying around a pair of sunglasses and always switching them out with your normal prescription glasses when walking out the door is inconvenient for many, and just plain impractical for others.
While intense sunlight glare will certainly motivate you to wear sunglasses, it’s too easy to forget on overcast days. You will also need to wear them while driving because the side windows of many cars don’t block UVA.
However, there is a simple remedy for this inconvenience. You can get a pair of Nike prescription glasses with clear lenses that either have built-in UV protection or have a UV protective coating applied to it. This is a set and forget solution because you’ll always wear your regular Nike prescription glasses since your vision depends on them.
This especially works well with children because they spend more time outdoors than adults. A significant amount of lifetime UV exposure occurs before the age of 18 years.
Lens Materials with Built-In UV Protection -Polycarbonate
By protection, we mean materials that block 100% of both UVA and UVB light. Polycarbonate does this. Therefore, a lens made from this material doesn’t require special treatment or coatings. An additional benefit of polycarbonate is that it’s extremely strong and impact resistant. This makes it the perfect lens material for kids. It has a higher index level than standard CR-39 plastic, which means polycarbonate requires less material (it’s thinner) than CR-39 for a given prescription level. However, its optical quality is less than that of CR-39.
Trivex blocks all (100%) UV light. It’s almost as resistant to impact as polycarbonate and also works well for kids. It has an optical quality comparable to CR-39 but costs twice as much as polycarbonate.
High Index Lens Plastics
Most high index lens plastics of 1.67 or higher have built-in UV protection as well. You should only consider these if you require high prescription glasses. These lenses cost more than either Trivex or polycarbonate and aren’t appropriate if you need low to medium prescription glasses.
Many plastic lenses will block some but not all UV radiation. If your lenses aren’t polycarbonate or Trivex and their labeling indicates less than 100% UV protection or has no UV protection indication at all, then you should get an additional coating that protects against all UV light.
If the idea of UV blocking glasses with clear lenses seems odd to you, it’s probably because you associate the dark tint of sunglasses with UV protection. However, this is a common misconception. Most tinted sunglasses also have either a UV blocking coating or are made from a UV blocking material. Tint by itself has nothing to do with UV blocking. A polarized lens by itself does not necessarily block all UV light either. If your current pair of prescription glasses doesn’t block all UV radiation, and this concerns you, contact us for more information.