It is important to protect your eyes against damage from the sun.  Much like protecting your skin from harmful UV rays of the sun with sunscreen, sunglasses are a must when on the beach or ski slopes and when driving to prevent glare.  In general, everyone should get in the habit of wearing sunglasses anytime their eyes are exposed to sunlight.  Everyone is at risk for eye damage from the sun year-round.  The risk is greatest from about 10 a.m. to 4 p.m.  Excessive sun exposure can cause loss of vision, cataracts, and even cancer of the eye.

UV rays are a part of sunlight that is an invisible form of radiation which can penetrate and change the structure of skin and eye cells, they are commonly divided into UVB and UVA rays, your sunglasses should block both forms.  UVB rays have shorter wavelengths and are the principle cause of sunburn, skin cancer, and premature aging of the skin.  UVA rays have longer wavelengths and penetrate more deeply, contributing to skin cancer and aging.   People who wear contact lenses that offer UV protection should still wear sunglasses.
 
There are many options to choose from when selecting sunglasses.  Primary concerns are usually fashion related but keep in mind that the main purpose of sunglasses are to protect your eyes.  Children should also wear sunglasses and not the toy versions, but real sunglasses that indicate the UV-protection level just as with adults.  Polycarbonate lenses are generally recommended for children because they are the most shatter-resistant.  Polarized sunglasses can be used for driving and, in fact, can reduce glare from a long, flat surface such as the hood of the car or the road’s surface.  Lightly tinted lenses block roughly 70 percent of UVB and 20 percent of UVA.  Medium-tinted lenses block about 95 percent of UVB and 60 percent of UVA.  Dark-tinted lenses block an average of 99 percent of UVB and 60 percent of UVA.  Sunglasses that wrap around or have side pieces sides offer protection from rays creeping in around the edges.  You could also ask an eye-care professional to test your sunglasses if you’re not sure of their level of UV protection. Any protection is better than no protection :)