pterygium

**Definition:** A triangular (wing-shaped) fibrovascular proliferation of bulbar conjunctiva that invades the cornea, crossing the limbus. Most often nasal (medial) and may be bilateral. Name derives from Greek "pterygion" = little wing.

**Pathophysiology:** - Chronic UV-B exposure is the main risk factor. UV damages limbal stem cells, causing elastotic degeneration of the subepithelial collagen, fibroblast proliferation, neovascularization, and chronic inflammation. - Other contributors: dry/dusty/windy environments, chronic irritation, and possibly HPV. Prevalence is higher in people with outdoor occupations (farmers, fishermen, surfers) and in tropical or equatorial regions ("surfer's eye"). It is more common in men and with increasing age. - Histology: elastotic (basophilic) degeneration of collagen, a Bowman's layer breach, and conjunctival epithelial hyperplasia with fibrovascular tissue. Pterygium invades and destroys Bowman's layer.

**Clinical features:** - Often asymptomatic. Symptoms include redness, foreign body sensation, tearing, and dryness. - Visual effects: induced corneal astigmatism (with-the-rule or against-the-rule depending on the lesion), and decreased vision if it reaches the visual axis. - Exam: a fleshy, triangular, vascularized tissue with its apex (head) on the cornea. A Stocker line (iron deposition) may be seen at the leading edge.

**Differential/key associations:** - **Pinguecula:** yellowish, raised conjunctival nodule at the limbus that does NOT cross onto the cornea. It is also related to UV exposure and may progress to pterygium. - **Pseudopterygium:** conjunctival scar adherent to the cornea after injury, inflammation, or chemical burn. It can occur at any location and is not attached at the limbus, so a probe can be passed beneath it. - **Conjunctival intraepithelial neoplasia/squamous cell carcinoma and other ocular surface neoplasia:** consider these if the lesion appears atypical (leukoplakic, papilliform, or gelatinous) or unilateral and rapidly growing.

**Management:** - Mild disease: UV-protective sunglasses/hats, artificial tears, and short courses of topical vasoconstrictors or topical steroids/NSAIDs for inflammation. - Surgical excision is indicated for visual axis involvement, significant astigmatism, persistent symptoms, restricted motility, or cosmesis. - Recurrence is the major complication. Using a conjunctival autograft with fibrin glue or sutures lowers recurrence compared with bare sclera excision. Adjuncts such as mitomycin C (antimetabolite) also reduce recurrence but carry a risk of scleral melt/necrosis.

**Boards pearls:** Nasal, wing-shaped conjunctival growth crossing the limbus onto the cornea in a patient with heavy sun exposure = pterygium. Pinguecula does not reach the cornea. Excision has a high recurrence rate, which is lowered with conjunctival autograft.