Pterygium
   Pterygium is a fleshy triangle injury that covers cornea from conjunctiva. Usually it is on the sides of the eyes. This injury is formed from benign connective tissue and conjunctiva vessels. 
   Pterygium reason: Ultraviolet rays of the sun are effective in formation of ptergiums. Sever wind, dust and dirt provoke eyes and they are effective in formation of ptergiums as well.