It Happened 50 Hours After Exposure to Sunglasses...
But you know what? Sunglasses also have a "shelf life", and if they work beyond their expiration date, they not only do not provide protection, but can cause damage to the eyes.
1.Exposure to sunlight can affect the UV resistance of sunglasses
Researchers at the University of S ? o Paulo in Brazil conducted simulation experiments in Europe, Australia, New Zealand, and South America. They placed sunglasses under a solar simulator, 30 centimeters from the light emitting point, and continued to "expose" them for 50 hours to see the degradation of their UV resistance.
The Daily Mail of England quoted researchers as saying that wearing sunglasses for two years is still safe. The sunlight varies in different regions of the world, with the highest UV levels in tropical countries and regions, even in winter, which means that the UV protection function of sunglasses degrades faster in these regions. In addition, residents in the southern hemisphere change sunglasses more frequently than those in the northern hemisphere. The researchers also said that prolonged exposure to sunlight not only affects the UV resistance of sunglasses, but also makes lenses more prone to breakage.
2.Weakened reflection indicates aging
Is this research reliable?
There are two main types of sunglasses, one is made of colored glass such as yellow and blue, which absorbs energy and refracts light from the body; The other type is the addition of a coating on the surface of the lens, which reflects ultraviolet light. The shelf life of sunglasses refers to the latter category of sunglasses. On the market, more than 80% of sunglasses are coated.
Generally speaking, this layer of coating is bonded to glass using a physical vapor deposition method. The plating film is generally made of metal materials such as gold, silver, and copper, and the metal materials will undergo oxidation, which will lead to their poor UV resistance.
However, different brands of sunglasses have different manufacturing methods. High priced sunglasses can be coated with several layers of coating, or coated with alloy materials, which has better stability and is not prone to oxidation. Just take a look at the reflective condition of the sunglasses. Newly purchased sunglasses look like mirrors. If the reflective condition becomes weak, it indicates that the coating has oxidized or even fallen off.
3.Eye injury due to extended service of sunglasses
What are the hazards of wearing "over age service" sunglasses for a long time?
The worst case scenario is that ultraviolet rays are directed directly into the eyes and have an impact.
The World Health Organization has published an article titled "Ultraviolet Radiation and Human Health", which points out that 5% of the 18 million people who lose sight due to cataracts worldwide each year are caused by ultraviolet radiation. Ultraviolet rays can also cause other serious eye diseases - keratitis, retinal damage, cataracts, macular degeneration, snow blindness, etc.
Fortunately, most people don't wear sunglasses for too long, even if the coating has fallen off, they won't face ultraviolet light for a long time. However, sunglasses that are out of their shelf life can also easily cause visual fatigue, dry eyes, and eye dryness, which can also lead to increased myopia.
Thank you for your reading
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