Did you know that the first sunglasses were worn by courtiers in 14th century China? The smoke-tinted lenses were designed, not to protect eyes, but to conceal their expression! Today, we need sunglasses for an entirely different reason: excessive sun exposure can cause loss of vision, cataracts, and cancer of the eye. Sunglasses offer protection, but what kinds are best?
Most of us do not get enough unprotected sunlight: most sources agree that we need at least 20 minutes a day. But sunglasses are a must when facing prolonged exposure. On the beach or the ski slopes, or when driving, sunglasses will not only prevent glare, but will protect your eyes from the harmful effects of UV rays.
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.
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.
Lightly tinted lenses block 70 percent of UVB and 20 percent of UVA.
Medium-tinted lenses block 95 percent of UVB and 60 percent of UVA.
Dark-tinted lenses block 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.