Aetiology

Ultraviolet (UV) light exposure appears to be a major factor in the development of pterygium as it is more common in people living in areas with high UV light exposure and those who work outdoors.[1]​​[2]​​[3] However, the aetiology of pterygia is not fully understood. Other potential causes include hereditary or immunological mechanisms, chronic ocular irritants, tear film anomalies, and the human papilloma and Epstein-Barr viruses.[1]​[6]​[7]​[8]​[9]​[10]​

Pathophysiology

Pterygia typically form on the nasal aspect of the cornea. Reasons for this are unknown. The temporal limbus may be shaded to a greater extent than the nasal limbus, by the eyelashes, eyelid curvature, and brow, or that total internal reflection within the cornea may focus light preferentially at the nasal limbus.​[11]

Dysfunction of the corneal epithelial limbal stem cells caused by chronic ultraviolet exposure may be important, disrupting the normal barrier that prevents the conjunctiva from growing onto the cornea.[12]​ Others have postulated that pterygium formation is primarily the result of a degenerative alteration of the conjunctiva rather than the limbal stem cells.

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