Pterygium

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**Pterygium**
*Classification & external resources*
ICD-10	H 11.0
ICD-9	372.4

Pterygium removal surgery

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 associated with, and thought to be caused by ultraviolet-light exposure (e.g. sunshine), low humidity, and dust. 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. The location of the line can give an indication of the pattern of growth. As it is a benign growth, it requires no treatment unless it grows to such an extent that it covers the pupil, obstructing vision. Some patients may also choose surgery if the growth becomes too unsightly. The exact cause is unknown. Wearing protective sunglasses with side shields and/or wide brimmed hats and using artificial tears throughout the day may 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.