Pterygium

Causes 
The cause is unknown, but it is more common in people with excess outdoor exposure to sunlight and wind, such as those who work outdoors. 

Risk factors are exposure to sunny, dusty, sandy, or windblown areas. Farmers, fishermen, and people living near the equator are often affected. Pterygium is rare in children. 

Symptoms 
The primary symptom of a pterygium is a painless area of elevated white tissue, with blood vessels on the inner or outer edge of the cornea. 

Treatment 
No treatment is required unless the pterygium begins to block vision -- then it should be removed with surgery. Wear protective glasses and a hat with a brim to prevent the condition from returning. 

Prevention 
Protecting the eyes from ultraviolet light may help prevent this condition.