Pterygiums are triangular overgrowths of the membrane covering the white of the eye called the conjunctiva. This conjunctiva normally only covers the white of the eye but when it grows and invades onto the clear cornea of the eye, we call this a pterygium. It is strongly associated with exposure to UV radiation and hot, dry climates. It is not a cancer and is thus not dangerous but all growths should be checked out to make sure it is not. If the pterygium does grow into the central cornea then the vision can be disturbed and surgical removal may need to be considered. The best protection against pterygiums is prevention by wearing sunglasses whenever outdoors as well as a brimmed hat.