Eye damage can be caused by exposure to ultraviolet rays. Consuming long hours in the sun can factor into the type of eye damage a person receives and how much. A couple of examples of eye damage are cataracts, pterygum, snow blindness, and retinal burn.
Cataracts are a very serious reaction to the sun and its UV rays. It causes a loss of clearness in the lens of the eye and clouds vision. If this damage is left untreated it is possible to lose eyesight completely. However, this can be cured with surgery.
Pterygum is another reaction eyes have to UV rays. It is a tissue growth on the white of the eye that hinders vision. It may also cause deterioration of the macula, which is the part of the retina where visual perception is the most clear.
Snow blindness is when the surface of the eye is burnt. The effects of the burn usually recede within just a couple days, but may cause problems in the future. Retinal burn is the last type of reaction that eyes experience in relation to the sun. It does not cause any pain. Therefore, a person may not realize their eyes are sun burnt because of the fact that they don’t experience any pain. The symptoms will emerge hours later, and by this time the damage is already done! It’s worth the while to wear sunglasses. It’s a safer alternative than no sunglasses at all.

References:

http://www.rsc.org/Publishing/ChemScience/Volume/2007/03