Protection from ultraviolet radiation.

The blue-violet part of the light spectrum is most dangerous to the eyes, as it easily passes through the cornea and lens, and its excess is causing to damage of a retina. Children, the elderly, patients with eye disease who had undergone surgery on the retina or the cornea (eg, laser vision correction), and without exception, blue-eyed blonds and representatives of Caucasoid type to suffer from bright sun in the spring and especially summer. But for the other it is not safe. Craftiness of excessive exposure to solar radiation consist in that person does not see or feel its, but over time it making itself felt.

Statutory requirements for sunglasses are regulated by national standards. According to them, there are three main groups of sunglasses - cosmetics (Cosmetic), conventional (General) and the glasses high degree of protection (High UV-protection). Cosmetic lenses - pink, purple, green and blue - are ineffective to protect and serve only as an accessory. Lenses high degree of protection required for high mountains and polar regions, equatorial-tropical regions, and conditions of ozone anomalies. And finally, lenses General - this summer lenses that meet the requirements of Europe and North America. Sunglasses with high level of UV protection can be with lenses of neutral, brown, greenish-brown color, but not with blue and purple. When choosing sunglasses, pay attention to their labeling. "UVA" and "UVB" shows the percentage of protection from ultraviolet rays (type "B" is considered the most harmful, and type "C" absorbed by the atmosphere). The designation "UV-400 nm" means that the lenses protect eyes from all UV light with wavelengths below 400 nm (the average length of light waves, reaching up to our eyes, - 290-380 nm). If the figure is less than 400, then still part of the rays is passed. Information about protection against infrared radiation does not write on the sunglasses usually and, as a rule, it is implied by default. Some lenses do it better than others, such as lens with polarization.

  

FYI: Every day the National Weather Service calculates the predicted UV Index for the next day in each area of the U.S.

Everyone knows to wear a hat or sun block to protect against ultraviolet radiation. But most overlook the importance eyewear play in protecting their eyes against ultraviolet harm.

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.)