Ultraviolet light is the component of sunlight most responsible for eye damage. Ultraviolet light rays come in three main types – A, B and C – categorized according to their wavelengths.

UV-C is the shortest and potentially the most dangerous wavelength, but it is largely absorbed by the Earth's atmosphere and therefore is less of a threat than UV-A or UV-B.

UV-A, a longer wavelength, usually induces skin tanning and browning and is responsible for premature skin aging.

UV-B, a shorter wavelength, causes sunburns and is most often associated with skin cancer. Additional studies show that long term exposure to UV radiation is one of the risk factors associated with cataracts.

Excessive exposure to UV light, especially from light reflected off sand, snow, or pavement, can produce a burn on the surface of the eye. Like a sunburn on the skin, eye surface burns are painful but usually temporary.

Long-term exposure of the eye to UV light affects not only its surface (cornea and conjunctiva), but also its internal structures (lens and retina). UV exposure is a risk factor in the development of cataracts, or clouding of the lens. Cataracts are one of the leading causes of reduced vision in the United States.

The American Academy of Ophthalmology, the world's largest association of eye physicians and surgeons, recommends protecting the eyes from harmful UV rays. Sunglasses with UV blocking lenses can help shield eyes from UV rays in sunlight.

However, even most sunglasses that offer UV protection block only about 50% of UV radiation because sunlight also enters the eye from above and around the sunglasses. Wearing a broad brimmed hat with sunglasses can further reduce exposure to UV rays, as can wearing UV blocking contact lenses in conjunction with sunglasses.

Source: http://www.jnj.com/