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TLDR: The answer is yes, both, depending. If your sunglass lenses aren’t made of the right materials, they won’t protect your eyes from UV damage, and if they’re too dark they may cause eyestrain. If your sunglass lenses are made of the right materials like polycarbonate, and they’re the right lightness or darkness, they will protect your eyesight and health and are good for you.
Now here’s the romance copy you can skip if you just wanted an answer, not an essay.
Sunlight – a double-edged sword
Without sunlight, there’d be no life on Earth. It’s easy to forget that as we slather our skin with sunscreen to avoid melanoma, or slap on hats and sunglasses to keep our face and eyes from frying. Our friend sunlight can be pretty intense, even on cloudy days. While its mostly welcome, sunlight does have some toxic aspects – namely, those invisible UV rays that cause the most damage to our delicate cells.
We value our sight and eyes. These two fragile organs help us define the world, filtering light reflecting off objects through our optic nerve for interpretation by our brains. Damage to our eyes affects how well they age. Physical impacts, UV exposure, bacterial and viral infections, diseases that cause nerve damage, alcohol consumption, dryness and strain, and even eye makeup can increase the risk to your eyes.
How do UV rays cause cancer and damage?
UV rays are a primary damaging factor for eyes. But how does ultraviolet light wreak such havoc?
All light is a form of radiation. While most radiation is benign as it lacks energy to cause cellular damage, certain types of radiation like UV are stronger and have the power to remove electrons from cells through ionization. This damages the DNA inside the cell, so that when the cell is replaced, it may become cancer. It also speeds up the process of cell replacement, which in turn speeds up aging. UVA, UVB, and UVC rays are all damaging, but UVC rays are mostly prevented from reaching us by the atmosphere. That’s why we’re mainly worried about UVA and UVB.
The process that damages and kills our skin and eye cells is the same one used to sanitize items from the bacteria on them. The UV light attacks the bacteria’s DNA and causes it to die. On the flip side, while it causes damage, UVB rays also stimulate the production of Vitamin D from the cholesterol in our skin. Talk about a trade-off. You get a vital vitamin you need for aging, while simultaneously being aged as your cells receive damage or expire and are replaced. That’s basically what happens when you get sunburned – whole swathes of skin just die off and are replaced.
Where and when are UV rays the strongest?
The atmosphere naturally filters out some UV rays, and not just UVC. People who live at lower elevations may take more time to become sunburned as the thicker atmosphere blocks UV light. People who live at higher elevations, or in mountainous areas, will need more protection because more UV light comes through the thinner atmosphere. The rays are also strongest at the height of day from 10 am to 4 pm for the same reason – traveling through the atmosphere at an angle blocks more UV, straight on blocks less. Spring and summer seasons, as well as living on the equator, will also raise UV exposure. Surprisingly, clouds block less UV light than you’d think, so wear sunscreen even if it’s cloudy outside.
UV exposure also occurs indoors! Beyond tanning beds, other sources of UV include black lights, mercury vapor lamps, plasma torches, mercury arc lamps and sanitizers, and even some car headlights. If you work in an industry where welding is frequently used, or at a tanning salon, don’t forget to wear protection for your skin and eyes.
The wrong lenses can be damaging
Since you can’t slather sunscreen on your eyes (please don’t), eyewear is your best choice to protect your eyes from UV. But not all eyewear provides the level of protection you need.
If the lenses are made from acrylic, but don’t have a filter that blocks UV light, then your eyes are not being protected. Most polarized sunglass lenses are made of acrylic, as it’s easier to secure the film on acrylic than on other plastics. Always check to make sure your polarized sunglasses also block 100% of UVA and UVB rays.
If you’re confident your eyes are protected when they aren’t, you may end up receiving more damage than you’re aware of. You may spend too long in a situation that will hurt your eyes, like hitting the slopes at the height of day with glaring white snow. Lenses that are made from actual glass or extra cheap plastics won’t block UV light – so find out what your lenses are made of!
What are the right lenses for you?
The primary material for most eyewear and sunglass lenses is polycarbonate. Polycarbonate plastic naturally has 100% UV protection, even without any colors or films applied. Polycarbonate is also a shatter-resistant plastic that is lightweight. However, it will scratch easily, so protect your lenses. Unlike acrylic films, though, scratches won’t remove any protective coating, and they’ll keep blocking those rays.
Eyewear may also use Trivex – which is more expensive because it provides more clarity, is rarer than polycarbonate, and is incredibly lightweight. Trivex also provides 100% UV protection.
Different uses and times of day require different colorations of your lens to prevent eyestrain. Darker gray and brown sunglasses work best at the height of day, where lighter amber, green, and yellow lenses work best in mornings, evenings, and cloudy days.
A gradient lens is a good way to prevent eyestrain. The lighter coloration at the bottom of the lens provides more clarity and focus at your hand level or below. This means you can see phone screens, dashboards, and books easier. The darker coloration at the top of the lens protects against ambient light.
Be aware of the edges!
While your lens might protect against all UV that directly hits it, it won’t protect against the sneaky rays that might come in from the side, top, or bottom. Some sunglasses – particularly wide temple or wrap around sports sunglasses – will help block that gap.
The trade-off with wide temples is that they may also block some of your peripheral vision. Sports wrap sunglasses are a good compromise, because the curve of the frame may allow for more vision on the side, while hugging the shape of your face to prevent light from sneaking in the edges. Full frame sunglasses often provide more coverage than half frame sunglasses, and we highly recommend the full curve shield sunglasses that keep peripheral vision AND mind the gap.
If you really want to protect against peripheral light, then we also suggest choosing sports goggles with polycarbonate lenses or optometrist-recommended sunglasses.
Protecting your eyeballs
It’s all about protection. Look for a UV 400* or 100% UV protection rating while you are searching for your next pair. Choose a lens color that feels the most comfortable for your eyes and choose a lens style with the features that work the best for you. If you have questions, reach out to your family physician or an optometrist.
*The UV 400 rating indicates the lenses protect beyond the UV range of light, up to 400 nanometers.