Pterygium
A pterygium is a wing-shaped growth of conjunctiva and fibrovascular tissue on the superficial cornea (Fig 6-2). As with pingueculae, the pathogenesis of pterygia is strongly correlated with UV light exposure, although environmental insults such as exposure to dust, wind, or other irritants causing chronic ocular inflammation may also be factors. The predominance of pterygia on the nasal side in the interpalpebral zone is theorized to result from light passing medially through the cornea, focusing on the nasal limbus area, while the shadow of the nose reduces the intensity of light transmitted to the temporal limbus. The prevalence of pterygia increases steadily with proximity to the equator, and the condition is more common in men than women, in persons 20–30 years of age (the most common age range for onset of pterygia), and in people who work outdoors. The histopathology of pterygia is similar to that of pingueculae (basophilic degeneration of elastotic fibers), except that a pterygium invades the superficial cornea, which is preceded by dissolution of the Bowman layer. For further discussion of the histopathology of both pingueculae and pterygia, see BCSC Section 4, Ophthalmic Pathology and Intraocular Tumors.
Astigmatism (regular and irregular), as well as corneal scarring, occurs in proportion to pterygium size. A pigmented iron line (Stocker line) may be seen in the cornea, anterior to the edge of the pterygium. A pterygium must be distinguished from a pseudopterygium, which may occur after trauma or chemical burns or secondary to inflammatory corneal disease. It is important to maintain an index of suspicion for carcinoma in situ or squamous cell carcinoma, primarily in patients with atypical presentations.
Treatment with artificial tears can alleviate associated ocular irritation, but as with pingueculae, long-term use of topical corticosteroids is contraindicated. Excision is indicated if the pterygium causes persistent discomfort or chronic irritation; exhibits progressive growth toward the central cornea or visual axis (>3–4 mm), causing blurred vision or irregular astigmatism; is cosmetically unacceptable; or restricts ocular motility. See Chapter 13 for discussion of the surgical treatment of pterygium.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.