Sunglasses Should Be Replaced Every Two Years

Many people use a pair of sunglasses for many years. In fact, sunglasses also have a shelf life, which is related to wearing time, lens material, wearing habits, and regional sunshine. Generally speaking, the best use period of sunglasses is roughly two years, after which it is best to replace them with a new pair.

First of all, the main wear and aging of sunglasses is the joint parts of the lens and the frame. There are currently three main types of lenses: resin polarizers, resin PC lenses (AC, CR39, and nylon are all temporarily classified into this category), and glass lenses. Lightweight and comfortable resin polarizer and resin PC lens are not wear-resistant, and will scratch over time. Many people do not know that the lenses are worn out, and relying on eye adjustment to try to see clearly will increase fatigue in the long run, resulting in decreased vision. Therefore, usually the lens should be put up to avoid scratches on the mirror surface.

Secondly, exposure to sunlight for a long time will reduce the ability of the lens to protect against ultraviolet rays and easily cause damage to the cornea. Through a simulation experiment, the researchers put the sunglasses under the sunlight simulator, 30 cm away from the luminous point, and continued to "expose" for 50 hours, and found that the UV protection ability of the lenses would be degraded. Tropical countries and regions have the highest levels of UV rays, which means that the UV protection of sunglasses degrades faster in these places. Even if the lens material of high-quality sunglasses is made of special materials, it will deteriorate over time. If the UV protection function of sunglasses is reduced, the cornea and retina will be damaged, and diseases such as solar keratitis and corneal endothelial damage will occur.

In addition, the sunglasses belong to the flat lens series, and only allow the diopter of plus or minus 8 degrees at most, beyond this error range is an unqualified product. According to market testing, nearly 30% of the diopter of sunglasses exceeds the error range, and some are even as high as 20 degrees. Consumers with normal vision wear this kind of sunglasses, just like wearing a pair of myopia or hyperopia glasses. After a summer, they will be "trained" into myopia or hyperopia patients by inferior glasses. Therefore, if you have symptoms such as dizziness, nausea, and dazzling after wearing sunglasses, you should take them off immediately.