How to choose sunglasses.

Look at the bright, colorful world of summer is just unbearably painful if you without sunglasses. When choosing their usually we are interested in two questions: "Is it fit to me?" and "How much?" Advanced customers can also ask about what kind of protection from ultraviolet radiation has favorite model. Here, properly speaking, all questions from average consumer to seller got to come to an end. But, if in choosing sunglasses seriously, but it should not be limited.

You should always pay attention to the material from which made the sunglasses, lenses color and marking. But first things first. Modern optical industry uses to make sunglasses glass and plastic. For a long time, glass lenses were considered the best material because it provides good protection from UV light and less distorted picture. Glass is more resistant to scratches, and its life longer. But in recent years, high-quality polymeric materials appeared, in no way inferior to the mineral (glass), and in some ways even superior to them, and many manufacturers now give preference to plastic. To protect your eyes from harmful radiation, in the manufacture of the plastic are employing special chemical compounds, and on a finished lenses are applied special coating. Sunglasses from such material are obtained light in weight and more practical than glass, which has one drawback - the fragility and traumatism (and therefore sunglasses with glass lenses are not recommended to wear for athletes and children). Plastic also has one drawback - the distortion of objects, but it can be verified by fitting of sunglasses: with qualitative lens, straight lines should not be distorted. Of course, sunglasses - a fashion accessory that adds your charm, mystery and solemnity. Still, their main purpose is different: to weaken the visible light to a comfortable feeling; further weaken the blue light range, the most dangerous to the retina and is the cause of photoretinit (burns the retina by light); to block ultraviolet light, causing a burns to the cornea and conjunctivitis; retain ability to distinguish between traffic signals.

There are five categories of lens opacity in sunglasses:

     0 - let pass 80-100% of the light (lens clear or lightly shaded);

     1 - let pass 43-80% of the light;

     2 - let pass 18-43% of the light;

     3 - 8-18% of the light is passed;

     4 - let pass 3-8% of the world (very dark lenses.)