Pterygium

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**Pterygium**
*Classifications and external resources*
ICD-10	H11.0
ICD-9	372.4

Pterygium usually refers to a benign growth of the conjunctiva. Alternately, it refers to any winglike triangular membrane occurring in the neck, eyelids, knees, elbows, ankles or digits (J Pediatr Orthop B 2004, 13:197-201). An example is popliteal pterygium syndrome, which affects the legs. The term comes from the Greek word pterygion meaning "wing".

When associated with the conjunctiva, a pterygium commonly grows from the nasal side of the sclera. It is caused principally by ultraviolet-light exposure (e.g. sunshine). 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, owing to the shadow cast by the nose.

[edit] Pathology

Pterygium in the conjunctiva is characterized by elastotic degeneration of collagen and fibrovascular proliferation. It has an advancing portion called the head of the pterygium, 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 it is found as an incidental finding in middle aged patients who spend a lot of time in the sun.