When we buy food, we are always used to looking at the shelf life, but do you know? Sunglasses also have a "shelf life"! According to the latest research results, the "shelf life" of a pair of sunglasses is about 2 years. After "expiration", sunglasses are likely to lose its role in protecting the eyes.
Inferior sunglasses are harmful
The reason why sunglasses can block ultraviolet rays is because a special coating film is added to the lens. After the lens is coated, it blocks and absorbs ultraviolet rays, and also blocks some useful light, which reduces the transmittance of the lens. Generally, the sunglasses with good quality have strong ability to block ultraviolet rays, and the transmittance is not much decreased, which does not affect the general visual clarity, and the lens coating film has a certain hardness, and the surface is not easy to wear.
Inferior sunglasses are completely different, not only the performance of blocking UV is not strong, the coating film is easy to break, and the transparency of the lens is seriously degraded. The eyes look like things in the dark room. At this time, the pupil will become larger, and the residual ultraviolet rays will be injected in large quantities. In the eyes, the eyes are damaged. Then the surface of the lens is not regular, and the external object is deformed and distorted, causing the eyeball to swell, and gradually experiencing visual fatigue symptoms such as nausea, loss of appetite, forgetfulness, and insomnia.
In view of this, when people buy sunglasses, they can make judgments based on whether the objects are clear or not. For the general public, to buy high-quality sunglasses, the only thing that can be done is to buy sunglasses at a regular optical shop.
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