Pterygium and pingueculum are variants of the same condition in which the conjunctiva (a membrane that covers the white of the eye) is damaged and responds by continuing to grow. In the case of a pterygium, the conjunctiva grows centrally onto the cornea, whereas in a pingueculum the conjunctiva only grows locally on the visible white of the eye.
Pterygia and pinguecula occur more often in people who spend a great deal of time outdoors, especially in sunny climates. Long-term exposure to sunlight, especially ultraviolet (UV) rays, and chronic eye irritation from dry, dusty conditions seem to play an important causal role in thickening the conjunctiva. Protecting the eyes from UV light by wearing sunglasses or a hat with a brim may help to prevent these conditions.
It is most commonly found on the nasal side of the cornea and represents a 'wing' (ptery is wing in Latin) of degenerated conjunctival tissue. A pterygium may be small or grow large enough to interfere with vision by obstructing the pupil. It can also distort the cornea, leading to astigmatism. In severe cases where the vision is affected, surgical removal is considered, although there is a risk the pterygium may grow back.
CAPTION: A small pterygium underneath a soft contact lens
Pinguecula most often occur in the visible white of the eye, adjacent to the edge of the cornea. They are often raised areas of abnormal conjunctival tissue that are generally slow to develop. Occasionally they can become inflamed - due to their raised nature they are the first part of the eye to dry out and are prone to frictional forces from the lids. Lubrication and sometimes therapeutic intervention is required.
CAPTION: A small, reasonably uninflammed pingueculum.