A pterygium grows in response to exposure to ultraviolet light. They are more common in light-skinned people living nearer the equator, particularly where outdoor activities are popular. The pterygium can decrease vision in several ways:   distortion of the corneal optics,  disruption of the tear film, growth over the center of the cornea, or induced anterior corneal scarring. Indications for surgery: 1. Growth over the corneal center. 2. Reduced vision due to corneal distortion. 3. Documented growth. 4. Symptoms of discomfort. 5. Cosmesis