Over time, the lenses are damaged and fail to protect the eyes from UV radiation. Scientists from Brazil have identified the shelf life of regular sunglasses. He was not more than two years of active use, writes The Daily Mail.
Moreover, experts recommend that manufacturers include this information on the packaging to safeguard consumers of the product. The inhabitants of southern countries need to change glasses more frequently, the inhabitants of the Nordic countries – less. However, it should be remembered that the service life of even the most quality points – no more than two or three years.
Constant sun exposure damages the lens. Old glasses more harmful to the eye than useful. At the moment, branded sunglasses is subjected to the test bright and direct sunlight for 50 hours without a break. However, scientists believe that such a test is not enough.
Preference is given to well-known brands that guarantee the quality of glasses. Forgery or threat to vision or do not protect against solar radiation.