Before buying sunglasses, make sure that its lens is appropriately manufactured. There is a simple way to do this. Wear the glasses; close or cover one of your eyes and with your other eye look at a rectangular surface, such as floor tiles. Then move the glasses slowly from side to side. Repeat the action, this time up and down. If the lines are viewed straight, the lenses have a fine quality. If it seems that the lines wiggle or move, especially in the center of the lens, it is better to try another pair.
For people who spend a lot of time in the sun, it is recommended to wear glasses with curved or highly curved frame. While these frames don't have a complicated structure, due to appropriate coverage of the eyes, they easily inhibit all harmful sun rays.