Why do some types of sunglasses damage your eyes? Why is it very essential that sunglasses must have ultraviolet protection (otherwise it is better not to use them at all)? What are ultraviolet rays?...
The UV rays are not visible to our eyes, but they are emitted from the sun together with the visible and non visible spectrum. In other words, they are sun rays that we don't see, but are pretty damaging to our skin and eyes. When we stay too long in the sun we get sunburn from these rays.
Now imagine these rays inside your eyes, or like it is otherwise called, in the retina. Retina is one of the most sensible part of our eyes. The light is captured there and thanks to the retina it is translated in neurological messages, which are deciphered by our brain and voila the images are seen. Do not think that the ultraviolet spectrum is bad, by any means! It is also good and thanks to it, we can produce the vitamin D in our skin.)
The lenses of sunglasses are composed of filters that form a barrier to a part of the sun’s visible spectrum rays, so in this way we can comfortable see in sunlight. But, when we put on the sunglasses the amount of light entering in our eyes is, in this way, reduced, resulting in the eyes being physiologically dilated. The major part of the sunglasses are so dark that even when our pupils are fully dilated, the amount of visible sunlight entering into our eyes doesn't make us uncomfortable.
The problem is the absence of ultraviolet filters in some cheap sunglasses, because if these kind of rays are not stopped and the pupils are dilated, the amount of UV-rays entering the retina will increase dramatically, resulting in damaging it! So, you can get retina burn just like sun burn of the skin! Especially if you use sunglasses without UV-filters in high latitude and snowing areas. Because the higher we are, the bigger is the amount of sun radiation that we take, especially UV-rays.
So, when you go skiing, sunglasses with UV protection are a must and if you like to wear normal sunglasses, be sure that they have the UV- protection filters, or don't use them at all.