The most familiar way to protect your eyes from the UV rays of the sun is by wearing sunglasses.

Sunglasses are able to block some UV rays that may cause damage to your eyes and help protect your eyes from harmful effects. If you think a wide-brimmed hat is enough to block out these harmful rays, think again: snow, water, dry sand, and sea foam are all able to reflect the sun’s UV rays back up into your face, making sunglasses essential for protecting your eyes.

You should wear sunglasses that block 100 percent UV whenever you are outdoors in daylight. Your eyes need protection even on cloudy days because the sun's damaging UV rays can penetrate cloud cover.

Sunglass frames with a “face-hugging” wraparound style provide the best protection because they limit how much sunlight reaches your eyes from all sides.

What is UV?

While many people refer to ultraviolet radiation as "UV light," this term technically is incorrect because you cannot see UV rays. Ultraviolet radiation is invisible.

There are three categories of UV radiation:

1. UVC: These are the highest energy UV rays and potentially could be the most harmful to your eyes and skin. Fortunately, the atmosphere's ozone layer blocks virtually all UVC rays. UVC rays have wavelengths that range from 100 to 280 nanometers (nm).

2. UVB: UVB rays have slightly longer wavelengths (280-315 nm) and lower energy than UVC rays. These rays are filtered partially by the ozone layer, but some still reach the earth's surface. In low doses, UVB radiation stimulates the production of melanin (a skin pigment), causing the skin to darken, creating a suntan. But in higher doses, UVB rays cause sunburn that increases the risk of skin cancer. 

Because the cornea appears to absorb 100 percent of UVB rays, this type of UV radiation is unlikely to cause cataracts and macular degeneration, which instead is linked to UVA exposure (see below).

3. UVA: UVA rays are closer to visible light rays and have lower energy than UVB and UVC rays. But UVA rays can pass through the cornea and reach the lens and retina inside the eye. Overexposure to UVA radiation has been linked to the development of certain types of cataracts, and research suggests UVA rays may play a role in development of macular degeneration.