- Deborah S Jacobs, MD
Deborah S Jacobs, MD
- Associate Professor of Ophthalmology, Part-Time
- Harvard Medical School
A pterygium is a triangular wedge of fibrovascular conjunctival tissue that typically starts medially on the nasal conjunctiva and extends laterally onto the cornea (picture 1). "Pterygium" refers to the shape of the tissue, which looks like an insect wing. The plural form of pterygium is pterygia.
A pterygium is sometimes thought of as a trivial problem, because it is unlikely to threaten visual acuity unless it approaches the visual axis. Nevertheless, it can be a cause of concern to patients because of the abnormal appearance it confers upon the eye and the irritation that is often associated with it. Although benign in the sense that pterygium is not cancerous, it can have important adverse effects on vision if proliferation approaches or reaches the visual axis.
This topic will focus on the clinical presentation, diagnosis, and treatment of pterygium. Some conditions that may occasionally be confused with pterygium are discussed in detail elsewhere. (See "Conjunctivitis" and "Blepharitis" and "Episcleritis" and "Photokeratitis".)
Worldwide prevalence of pterygium varies from 1 to 25 percent, depending on the population studied [1-6]. Pterygium occurs more commonly in tropical regions, although the exact mechanisms for this are not well-known [7-9]. The prevalence of pterygium is associated with chronic sun exposure  and specifically to ultraviolet (UV) light [11-13], which may partly explain the geographic variation in prevalence.
Several population-based studies have found higher rates of pterygium to be associated with older age, male sex, fewer years of education, and outdoor job location [2,6,14-16]. In the Barbados Eye Study, approximately one-fourth of the black participants had pterygium, a frequency that was 2.5 to 3 times higher than among whites in this study . Among black participants, lower rates of pterygium were associated with darker skin complexion. Lower rates were also associated with always using sunglasses outdoors and using prescription glasses [1,16]. One study in Australia found a higher rate of pterygium in rural areas compared to urban areas (6.7 and 1.7 percent, respectively), partly as a result of ocular sun exposure .
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