Try not to be deceived by the colour or cost of your sunglasses. Each pair's level of protection against harmful UV rays is different. As your eyes absorb light, which is a form of energy, the process creates heat or chemical reactions in the eye tissue. These reactions can damage the eye's natural ability to heal itself and cause some types of cancer. Knowing what to look for in a good pair of sunglasses' UV protection can protect your eyes against damage from UV rays, bright light and blue light that dances off summer water.
Put the sunglasses on. Looking at a rectangular pattern, such as floor tiles, move your head up and down and side to side. If the lines stay straight, then the amount of distortion is acceptable.
Hold the pair out in front of yourself and look for a uniform tint across the whole lens. If the lens is darker in one area than another, the UV protection is not effective for the whole eye. Deep scratches that appear lighter or clear in the tint of your lenses reduce UV protection, as well.
Hold the glasses at an arm's length. Look through them at a straight line in the distance, like the edge of a door. Slowly, move the lens across the line of the door edge. Any hint of distortion -- the straight edge sways, curves or moves -- means the lens is flawed.
Try the glasses on in front of a mirror. If you can see your eyes easily through the lenses, they are too light to block all UV and UVB rays.
Check the label. It should say the lenses block 99-100 per cent of UV rays or claim UV absorption up to 400nm, which is the same as 100 per cent UV blockage.