A pterygium is an elevated, superficial, external ocular mass that usually forms over the perilimbal conjunctiva and extends onto the corneal surface. Pterygia can vary from small, atrophic quiescent lesions to large, aggressive, rapidly growing fibrovascular lesions that can distort the corneal topography, and, in advanced cases, they can obscure the optical center of the cornea. [1, 2]
The pathophysiology of pterygia is characterized by elastotic degeneration of collagen and fibrovascular proliferation, with an overlying covering of epithelium. Histopathology of the abnormal collagen in the area of elastotic degeneration shows basophilia with hematoxylin and eosin stain. This tissue also stains with elastic tissue stains, but it is not true elastic tissue, in that it is not digested by elastase. [1, 2]
Occurrence within the United States varies with geographical location. Within the continental United States, prevalence rates vary from less than 2% above the 40th parallel to 5-15% in latitudes between 28-36°. A relationship is thought to exist between increased prevalence and elevated levels of ultraviolet light exposure in the lower latitudes. [3, 4]
Internationally, the relationship between decreased incidence in the upper latitudes and relatively increased incidence in lower latitudes persists.
Pterygia can cause a significant alteration in visual function in advanced cases. They also can become inflamed, resulting in redness and ocular irritation.
Pterygia are reported to occur in males twice as frequently as in females.
It is uncommon for patients to present with pterygia prior to age 20 years. Patients older than 40 years have the highest prevalence of pterygia, while patients aged 20-40 years are reported to have the highest incidence of pterygia.
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