It may occur in both eyes. The cause is unknown, but it may be the result of exposure to ultraviolet light.
Risk factors are exposure to sunny, dusty, sandy, or windblown areas.
It is rare in children. Protective glasses should be worn to prevent recurrences in people who work outdoors. The probable outcome is good. Call for an appointment with your health care provider if symptoms develop. Call for an appointment with your health care provider if you have had a pterygium in the past and symptoms recur.