Introduction
Background
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.
Pathophysiology
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.
Frequency
United States
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.
International
Internationally, the relationship between decreased incidence in the upper latitudes and relatively increased incidence in lower latitudes persists.
Mortality/Morbidity
Pterygia can cause a significant alteration in visual function in advanced cases. They also can become inflamed, resulting in redness and ocular irritation.
Sex
Pterygia are reported to occur in males twice as frequently as in females.
Age
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.
Clinical
History
Patients with pterygia present with a variety of complaints, ranging from no symptoms to significant redness, swelling, itching, irritation, and blurring of vision associated with elevated lesions of the conjunctiva and contiguous cornea in one or both eyes.
Physical
A pterygium can present as any of a range of fibrovascular changes on the surface of the conjunctiva and the cornea. It is more common for the pterygium to present on the nasal conjunctiva and to extend onto the nasal cornea, although it can present temporally, as well as in other locations.
- The clinical presentation can be divided into 2 general categories, as follows:
- One group of patients with pterygium can present with minimal proliferation and a relatively atrophic appearance. The pterygia in this group tend to be flatter and slow growing and have a relatively lower incidence of recurrence following excision.
- The second group presents with a history of rapid growth and a significant elevated fibrovascular component. The pterygia in this group have a more aggressive clinical course and a higher rate of recurrence following excision.
Causes
- Risk factors for pterygium include the following:
- Increased exposure to ultraviolet light, including living in subtropical and tropical climates
- Engaging in occupations that require outdoor activities
- A genetic predisposition to the development of pterygia appears to exist in certain families.
- A predilection exists for males to develop this condition in significantly higher numbers than females, although this finding may represent an increased exposure to ultraviolet light in this portion of the population.
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Further Reading
Keywords
pterygia, ocular mass, ocular lesion, corneal surface, corneal topography, diplopia, double vision, vision loss
