The sun is a natural source of ultraviolet (UV) radiation. The development of many eye diseases is associated with excessive exposure to UV radiation. If you think that UV radiation can only lead to long-term consequences, you are mistaken.
People resting in the mountains or at sea without sunglasses can almost immediately feel discomfort in their eyes. After 6-12 hours of being in the bright sun, severe lacrimation, photophobia, complaints of redness of the eyes and a feeling that there is a foreign object in the eyes may appear. These are signs of photokeratitis, a painful eye condition caused by exposure of insufficiently protected eyes to the ultraviolet rays. This condition leads to a decrease in vision, which can last up to 48 hours.
Both adults and children regardless of skin pigmentation are highly likely to damage their eyes due to UV radiation. It is important to remember that the damage from UV radiation is cumulative, it accumulates throughout life.
It is proved by eye doctors that 80% of the lifetime dose of UV radiation we receive by the age of 18. The UV radiation can not be blocked by fog or clouds. The highest amount of UV radiation you risk getting is in the middle of the day, at high altitudes and when light is reflected from water or snow.
The most important guideline in choosing glasses is the reliability of the UV filter. Sunglasses should block 100% of the harmful radiation. Give preference to lenses marked with UV400 and remember that the color intensity of the lenses does not affect this protective ability.
The lens material can be glass, plastic, polycarbonate, next-generation polyurethane (NXT) and acrylic. The main thing is that the lens should have high optical properties and not distort color perception.
Sunglasses vary in light transmission. There are five categories of filters. They are indicated by a number from 0 to 4 (usually it is indicated on the inner surface of the lens). The filter marked “0” transmits from 80 to 100% of the light, with “4” it’s from 3 to 8%. In a city for driving a car, the first or second category of the filter is enough but for a trip to the sea or to the mountains, only the third or fourth.
The color of the lenses depends on your preferences and lifestyle. The most comfortable for the eyes are gray, brown or green lenses. The choice of additional coverage depends on the purpose of the sunglasses.
Polarized glasses allow you to feel comfortable even in the brightest light and reliably block sun glare. Such glasses are recommended for driving a car, playing sports in the mountains and beach holidays.
There are special photochromic lenses. They change their color depending on the external lighting. In the room, they are transparent or with a little tint and darken on the street. Drivers should choose special photochromic lenses as car glass blocks most of the UV radiation, under the influence of which the lens changes color.
Sunglasses should be bought only in trusted optics stores. If you doubt the quality of the UV filter, contact the optics salon where the degree of protection against UV radiation can be checked using a special device (spectrophotometer).
Remember that it is better to be completely without glasses than in dark glasses without proper UV protection. In sunshine, our pupils reflexively decrease in diameter, limiting the harmful effects of UV radiation on the lens and retina. If you are wearing sunglasses without a UV filter, the pupil will remain wide and even more harmful radiation will penetrate the eye. If you doubt the quality of the sunglasses, it is better to refrain from buying them.