In this way, they trick the eye: the pupil dilates more to detect less light, but in the eye comes a greater amount of harmful ultraviolet and infrared radiation, thereby increasing the risk of eye injury. The problem is that solar radiation is stored in the lens and not deleted. The eyes have solar capital, ie the effect of radiation is cumulative. In addition, poor quality glasses lenses tend to have irregularly carved, so that users can get without being aware of it, sunglasses with a small graduation and suffer headaches hours after for this reason. Legislation Community 1997 (1836) contains a set of standards to be met before the glasses on the market. First, it must pass the laboratory tests, from the mechanics, and assess possible to deform the frame, to measurements with a spectrophotometer to analyze the ability to filter visible light and ultraviolet rays. After passing these checks, they get the 'CE' minimum quality criteria, although some markets and bazaars glasses look the brand without having passed quality inspection.
Therefore, we must also establish that this type-approval is accompanied by an extra-label usually attached to the pin on which are also given instructions for cleaning and maintenance, where the manufacturer or importer to take responsibility for that section meets European guarantees. In addition to the CE, that attention must be on the label or sticker affixed to the lens to provide certain information such as sunscreen, legislation that meets or whether it protects or not against lightning ultraviolet (UV). The zero is used for low-light conditions for the winter or very overcast skies. Zero filter glasses absorb 20% of sunlight. Filter 1 is most appropriate for spaces with low light solar cities with moderate light and sun, as these lenses absorb up to 56% of the radiation. The filter 2 is used for sites with medium light, including bright winters. Ideal for sports like running or biking, and are, along with 3 filter lenses, best-selling glasses.
The filter 3 is suitable for environments with a solar light, such as that on a sunny day at the beach or the countryside and absorbs up to 90% of the light. Finally, the filter 4 is designed for sunglasses that are used in mountain sports is greater than 3. 000 meters, or water. Solar absorption capacity, which reaches 97%, makes them unsuitable for driving, because in a shaded tunnel or unduly limit vision. In choice of sunscreen, the color of the eye itself also a factor. The users should take extra precautions are blue eyes, and behind them the green eyes, and finally, those of darker brown eyes. The price may be indicative of quality, and in fact the most expensive glasses tend to be of good quality, but, and here is the key, there are cheaper and of satisfactory quality. A comparative analysis of the magazine published last summer, which studied 20 glasses whose prices ranged from 12.90 to 286 euros, found that all met the stringent tests of the European standard EN 1836:2006 which regulates the quality of sunglasses. That is, the twenty filtered ultraviolet radiation almost completely, were fit to drive and pass the tests of resistance. Optical specialists argue that in glasses with such a difference in the price differences are not reflected in sun protection, but in quality and clarity of vision. It seems very likely to be so, but the truth is that what matters in health is protection from the sun, the eye health. Others