Pterygium (ophthalmology)

In ophthalmology, a pterygium is a degenerative condition of the eye affecting the conjunctiva and the cornea. It it thought to be an irritative phenomenon associated with exposure to ultraviolet light and is found particularly in people who work outdoors in hot, dusty climates. Globally there is a relationship between decreased incidence in the upper latitudes and relatively increased incidence in lower latitudes - this is thought to be because of elevated levels of ultraviolet light exposure in the lower latitudes.

• are seen as wedge-shaped lesions spreading onto the cornea almost always from the nasal side (1)
• pathologically, it is a degeneration of Bowman's membrane of the cornea which extends into the conjunctival epithelium. The process usually begins at the medial and lateral borders of the cornea. It progresses towards the centre taking with it a continuation of the conjunctival epithelium
• the condition is usually asymptomatic. The highest prevalence is in patients over the age of 40 years, while patients aged 20-40 years are reported to have the highest incidence of pterygia (1). It is uncommon for patients to present with pterygia prior to age 20 years.
• visual disturbances may result from encroachment on the pupillary area.
• it may be removed surgically but recurrence is common. Protective glasses for outdoor work are advised.

The conjunctival lesions are identical to those of pingueculae. Note that pterygia and pingueculae are both benign growths on the surface of the eye - the only distinguishing difference is that pterygia grow over the edge of the cornea.