A pterygium, meaning wing, is a benign growth of the conjunctiva. It more commonly tends to grow from the nasal side of the sclera. It is caused principally by damage from ultraviolet sun exposure. It appears predominantly on the nasal side because the cornea acts as a lens for sunlight on the medial/nasal side but not on the lateral/temporal side due to the shadow cast by the nose.
Pathology
Pterygium is characterized by elastotic degeneration of collagen and fibrovascular proliferation.
It has an advancing portion called the head of the pteygium, which is connected to the main body of the pterygium by the neck. Sometimes a line of iron deposition can be seen adjacent to the head of the pterygium called Stocker's line. As it is a benign growth , it requires no treatment unless it grows to such an extent that it covers the pupil, obstructing vision. Wearing protective sunglasses with side shields will help prevent their formation or stop further growth.
Occasionally found as an incidental finding in middle aged patients who spend a lot of time in the sun.