A pterygium is a benign, wedge shaped growth consisting of conjunctival tissue that extends onto the cornea.
Some become inflamed and red at times, while others may be large and/or thick, causing discomfort or interfering with vision. Generally, however, it may be safely left alone. It is not a cancer, nor will it develop into a cancer.
Pterygia are more likely to develop in people who spend a lot of time in the sun. The actual cause is unknown, however genetic factors may feature, as pterygia can run in families. Many need no treatment.