Summer is here, and the sun is scorching. With increased health awareness, more and more people are wearing sunglasses when they go out. For many, the reasons for replacing sunglasses are mostly that they're broken, lost, or no longer fashionable… But actually, there's another important reason that's often overlooked: sunglasses have "aged and failed."
Recently, we've often seen articles reminding people that "sunglasses only last two years and should be replaced after that." But is it really true that sunglasses only last two years?
Sunglasses Really "Aging"
The base material of sunglasses lenses can absorb some ultraviolet (UV) rays, and the coating on the lenses can reflect some UV rays. Many sunglasses also incorporate UV-absorbing materials into their lenses. This effectively blocks the vast majority of UV rays, preventing them from harming our eyes.
However, this protection is not permanent.
Because ultraviolet (UV) rays carry high energy, they cause the materials of sunglasses to age, reducing the ability of the sunscreen ingredients to absorb UV rays. The shiny coating on sunglasses is actually the result of metal vapor deposition, and these coatings can wear down and oxidize, reducing their reflectivity. All of these factors diminish the sunglasses' UV protection capabilities.
Furthermore, if we don't take care of our sunglasses, we often cause problems such as direct lens wear, loose temples, and deformation or damage to the frame and nose pads. All of these issues affect the normal use and protective effect of the sunglasses.
Is it really necessary to replace sunglasses every two years?
First, let me clarify that this is not a rumor, but a real study.
Professor Liliane Ventura and her team at the University of São Paulo, Brazil, conducted extensive research on sunglasses, and in one of their papers, they did indeed recommend replacing sunglasses every two years. [1] This conclusion has been cited by many media outlets, and we often see similar content in Chinese today.
However, this conclusion has a premise: the researchers calculated it based on the workload of wearing sunglasses in Brazil… that is, if sunglasses are worn for 2 hours a day, their UV protection will decrease after two years, and they should be replaced.
How to Make Your Sunglasses Last Longer
A good pair of sunglasses is often expensive. If we take good care of them, we can make them protect us for longer. Specifically, we just need to:
Store them promptly when not in use to prevent scratches or direct sunlight.
For drivers, never leave your sunglasses on the dashboard to be exposed to direct sunlight.
When temporarily storing sunglasses, remember to keep the lenses facing upwards to avoid scratches.
Use an eyeglass case or pouch, as these specialized storage containers have soft interiors that won't damage the lenses.
Never casually stuff your sunglasses into your pocket or toss them into your backpack where they can rub against other items like keys, wallets, and phones. This can easily damage the lens coating and may even crush the frame.
When cleaning sunglasses, use dish soap, hand soap, or other cleaning agents to create foam and clean the lenses. Rinse thoroughly and pat dry with a lens cloth, or use dedicated wet lens wipes. This method is less likely to cause scratches than dry wiping.
Wear sunglasses correctly. Don't wear them high on your head, as they are easily knocked off and broken, and the temples may be damaged.
Just Remember These Tips When Choosing Sunglasses
Choosing good sunglasses isn't difficult at all. Just look for sunglasses with the "UV400" or "UV100%" label in reputable stores. These labels indicate that the sunglasses offer nearly 100% protection against ultraviolet rays, which is sufficient for protection.
So how do you choose the color? Generally, for everyday use, prioritize brown or gray lenses, as they have less impact on the color of objects and are more convenient for daily use, especially while driving, as they won't affect the driver's ability to see traffic lights. Additionally, drivers can choose sunglasses with polarized lenses to reduce glare and improve driving comfort.
One easily overlooked aspect when choosing sunglasses is the "shape." It's easy to see that larger sunglasses with a curved shape that fits the face offer the best sun protection.
If sunglasses are the wrong size, the curvature doesn't fit our face shape, or the lenses are too small, even if the lenses have adequate UV protection, light will easily leak through, significantly reducing their sun protection effect.
We often see articles claiming that you can determine the reliability of sunglasses by using a counterfeit money detector lamp and a banknote. The argument is that sunglasses block UV rays, and the counterfeit money detector lamp won't be able to illuminate the security features through them.
This claim is debatable, as it depends on the power and wavelength of the counterfeit money detector lamp. Many counterfeit money detector lamps have very low power and fixed wavelengths; some ordinary glasses can block the UV rays emitted by these lamps, preventing the security features on the banknote from illuminating. Therefore, it's safer to use professional instruments to determine the protective ability of sunglasses. For ordinary consumers, it's most important to look for "UV400" and "UV100%".
In conclusion, sunglasses do "expire and deteriorate," but we don't need to replace them every two years.
