A pterygium is a growth of tissue that extends from the conjunctiva to the cornea. It is caused by chronic exposure to Sunlight (UV), wind and conditions that dry out the eye. It can become large enough to cause visual distortion and moderate to severe dry eye symptoms. To prevent the growth of pterygia, it is important to keep your eyes moist with artificial tears, and use appropriate UV blocking sunglasses. Pterygia can also be surgically removed if it is causing visual distortion or symptoms of discomfort.