When choosing bifocal eyeglasses, at first you should know your purpose: for sun-shading, clothes matching, or for decoration? Besides sun-shading, whether it has the functional requirements of preventing ultraviolet? Is there any special requirement for the lens safety function? Only if you clear these objectives and combine the style and the actual effect on my face, can you purchase a pair of suitable sunglasses.
In order to protect your eyes, you can choose anti-ultraviolet sunglasses and eliminate the ultraviolet below 380nm as much as possible. Sunglasses with a safety function have lens made of PC and other materials which resist attacks. For motorcycle riders, drivers and other consumers who have special requirements on the safety performance, it is a good choice.
Consumers should ask for complete package, which is the promise given by the factory about products quality. Or asking the merchants to specify these additional protective function on the invoice, in the event of disputes, you would not be passive because of lack of evidence.
You should choose the colors of sunglasses according to the places for activities. The color of bifocal glasses should have sufficient depth in order to block the light in summer. However, riders and drivers mustn't choose dark-colored lens; otherwise, the discriminating ability will be affected, or even accidents may happen.
The color of sunglasses can’t be bias and won’t make distortion of colors of around scenery. Before wearing sunglasses, observe objects of red, green and yellow colors first. And then put on sunglasses to observe the same objects to test whether the lenses have the color problem.
It is best to choose light gray, brown or smoke color sunglass lens. The following is green, amber, blue and so on, the red is only used for sun bath or on the snowfield. Improper wearing of sunglasses may cause eye illness. It is unnecessary to wear sunglasses in cloudy days and indoors.
Some people wear sunglasses no matter which occasion it is and no matter the sunlight is stronger or weaker. This will increase the burden of eye adjustment necessarily, cause the tension and fatigue of eye muscle and letdown the vision. The infants and children whose visual system development is still not perfect should not wear sunglasses.
In addition to glass sunglasses, the wearing resistance of other lens materials is not great. Users should often pay attention to the surface of the bifocal lens, and change it timely when definition is affected by heavy wear.
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